TY - JOUR A1 - Abbas, Ioana M. A1 - Vranic, Marija A1 - Hoffmann, Holger A1 - El-Khatib, Ahmed H. A1 - Montes-Bayón, María A1 - Möller, Heiko Michael A1 - Weller, Michael G. T1 - Investigations of the Copper Peptide Hepcidin-25 by LC-MS/MS and NMR⁺ JF - International Journal of Molecular Sciences N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others. KW - hepcidin-25 KW - copper KW - nickel KW - copper complex KW - ATCUN motif KW - metal complex KW - MS KW - NMR structure KW - metal peptide KW - metalloprotein KW - metallopeptide KW - isomerization KW - racemization KW - purity KW - reference material Y1 - 2018 U6 - https://doi.org/10.3390/ijms19082271 SN - 1422-0067 SN - 1661-6596 VL - 19 IS - 8 PB - Molecular Diversity Preservation International CY - Basel ER - TY - JOUR A1 - Abbasi, Ali A1 - Xu, Yaolin A1 - Khezri, Ramin A1 - Etesami, Mohammad A1 - Lin, C. A1 - Kheawhom, Soorathep A1 - Lu, Yan T1 - Advances in characteristics improvement of polymeric membranes/separators for zinc-air batteries JF - Materials Today Sustainability N2 - Zinc-air batteries (ZABs) are gaining popularity for a wide range of applications due to their high energy density, excellent safety, and environmental friendliness. A membrane/separator is a critical component of ZABs, with substantial implications for battery performance and stability, particularly in the case of a battery in solid state format, which has captured increased attention in recent years. In this review, recent advances as well as insight into the architecture of polymeric membrane/separators for ZABs including porous polymer separators (PPSs), gel polymer electrolytes (GPEs), solid polymer electrolytes (SPEs) and anion exchange membranes (AEMs) are discussed. The paper puts forward strategies to enhance stability, ionic conductivity, ionic selectivity, electrolyte storage capacity and mechanical properties for each type of polymeric membrane. In addition, the remaining major obstacles as well as the most potential avenues for future research are examined in detail. KW - Ionic selectivity KW - Ionic conductivity KW - Gel polymer KW - Ion exchange KW - Porous KW - polymer Y1 - 2022 U6 - https://doi.org/10.1016/j.mtsust.2022.100126 SN - 2589-2347 VL - 18 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdissa, Negera A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Ndakala, Albert A1 - Majer, Zsuzsanna A1 - Neumann, Beate A1 - Stammler, Hans-Georg A1 - Sewald, Norbert A1 - Yenesew, Abiy T1 - A xanthone and a phenylanthraquinone from the roots of Bulbine frutescens, and the revision of six seco-anthraquinones into xanthones JF - Phytochemistry letters N2 - Phytochemical investigation of the dichloromethane/methanol (1:1) extract of the roots of Bulbine frutescens led to the isolation of a new xanthone, 8-hydroxy-6-methylxanthone-1-carboxylic acid (1) and a new phenylanthraquinone, 6',8-O-dimethylknipholone (2) along with six known compounds. The structures were elucidated on the basis of NMR and MS spectral data analyses. The structure of compound 1 was confirmed through X-ray crystallography which was then used as a reference to propose the revision of the structures of six seco-anthraquinones into xanthones. The isolated compounds were evaluated for cytotoxicity against human cervix carcinoma KB-3-1 cells with the phenylanthraquinone knipholone being the most active (IC50 = 0.43 mu M). Two semi-synthetic knipholone derivatives, knipholone Mannich base and knipholone-1,3-oxazine, were prepared and tested for cytotoxic activity; both showed moderate activities (IC50 value of 1.89 and 2.50 mu M, respectively). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. KW - Bulbine frutescens KW - Xanthone KW - seco-Anthraquinone KW - Phenylanthraquinone KW - Cytotoxicity KW - Structure revision Y1 - 2014 U6 - https://doi.org/10.1016/j.phytol.2014.04.004 SN - 1874-3900 SN - 1876-7486 VL - 9 SP - 67 EP - 73 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdissa, Negera A1 - Induli, Martha A1 - Akala, Hoseah M. A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Ndakala, Albert A1 - Yenesew, Abiy T1 - Knipholone cyclooxanthrone and an anthraquinone dimer with antiplasmodial activities from the roots of Kniphofia foliosa JF - Phytochemistry letters N2 - A new phenylanthrone, named knipholone cyclooxanthrone and a dimeric anthraquinone, 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol were isolated from the roots of Kniphofia foliosa together with the rare naphthalene glycoside, dianellin. The structures were determined by NMR and mass spectroscopic techniques. The compounds showed antiplasmodial activities against the chloroquine-resistant (W2) and chloroquine-sensitive (D6) strains of Plasmodium falciparum with 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol being the most active with IC50 values of 1.17 +/- 0.12 and 4.07 +/- 1.54 mu g/ml, respectively. KW - Kniphofia foliosa KW - Asphodelaceae KW - Roots KW - Anthraquinone KW - Knipholone cyclooxanthrone KW - 10-Methoxy-10,7 '-(chrysophanol anthrone)-chrysophanol KW - Dianellin KW - Malaria Y1 - 2013 U6 - https://doi.org/10.1016/j.phytol.2013.02.005 SN - 1874-3900 VL - 6 IS - 2 SP - 241 EP - 245 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdou, Nicole A1 - Alonso, Bruno A1 - Brun, Nicolas A1 - Landois, Perine A1 - Taubert, Andreas A1 - Hesemann, Peter A1 - Mehdi, Ahmad T1 - Ionic guest in ionic host BT - ionosilica ionogel composites via ionic liquid confinement in ionosilica supports JF - Materials chemistry frontiers N2 - Ionosilica ionogels, i.e. composites consisting of an ionic liquid (IL) guest confined in an ionosilica host matrix, were synthesized via a non-hydrolytic sol-gel procedure from a tris-trialcoxysilylated amine precursor using the IL [BMIM]NTf2 as solvent. Various ionosilica ionogels were prepared starting from variable volumes of IL in the presence of formic acid. The resulting brittle and nearly colourless monoliths are composed of different amounts of IL guests confined in an ionosilica host as evidenced via thermogravimetric analysis, FT-IR, and C-13 CP-MAS solid-state NMR spectroscopy. In the following, we focused on confinement effects between the ionic host and guest. Special host-guest interactions between the IL guest and the ionosilica host were evidenced by H-1 solid-state NMR, Raman spectroscopy, and broadband dielectric spectroscopy (BDS) measurements. The three techniques indicate a strongly reduced ion mobility in the ionosilica ionogel composites containing small volume fractions of confined IL, compared to conventional silica-based ionogels. We conclude that the ionic ionosilica host stabilizes an IL layer on the host surface; this then results in a strongly reduced ion mobility compared to conventional silica hosts. The ion mobility progressively increases for systems containing higher volume fractions of IL and finally reaches the values observed in conventional silica based ionogels. These results therefore point towards strong interactions and confinement effects between the ionic host and the ionic guest on the ionosilica surface. Furthermore, this approach allows confining high volume fractions of IL into self-standing monoliths while preserving high ionic conductivity. These effects may be of interest in domains where IL phases must be anchored on solid supports to avoid leaching or IL spilling, e.g., in catalysis, in gas separation/sequestration devices or for the elaboration of solid electrolytes for (lithium-ion) batteries and supercapacitors. Y1 - 2022 U6 - https://doi.org/10.1039/d2qm00021k SN - 2052-1537 VL - 6 IS - 7 SP - 939 EP - 947 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Abegaz, Berhanu M. A1 - Peter, Martin G. T1 - Emodine and emodinanthrone rhamnoside acetates from fruits of rhamnus prinoides Y1 - 1995 SN - 0031-9422 ER - TY - JOUR A1 - Abouserie, Ahed A1 - Zehbe, Kerstin A1 - Metzner, Philipp A1 - Kelling, Alexandra A1 - Günter, Christina A1 - Schilde, Uwe A1 - Strauch, Peter A1 - Körzdörfer, Thomas A1 - Taubert, Andreas T1 - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry. KW - Ionic liquids KW - Alkylpyridinium salts KW - Structure elucidation KW - Phase transitions Y1 - 2017 U6 - https://doi.org/10.1002/ejic.201700826 SN - 1434-1948 SN - 1099-0682 SP - 5640 EP - 5649 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Abouserie, Ahed A1 - Zehbe, Kerstin A1 - Metzner, Philipp A1 - Kelling, Alexandra A1 - Günter, Christina A1 - Schilde, Uwe A1 - Strauch, Peter A1 - Körzdörfer, Thomas A1 - Taubert, Andreas T1 - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry. KW - Ionic liquids KW - Alkylpyridinium salts KW - Structure elucidation KW - Phase transitions Y1 - 2017 U6 - https://doi.org/10.1002/ejic.201700826 SN - 1434-1948 SN - 1099-0682 SP - 5640 EP - 5649 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Adamovich, Sergey N. A1 - Mirskova, Anna N. A1 - Mirskov, Rudolf G. A1 - Schilde, Uwe T1 - Synthesis and crystal structure of 1,4,10,13-tetraoxa-7,16-diazoniumcyclo-octadecane bis(4-chloro-2-methyl-phenoxyacetate) JF - Chemistry central journal N2 - The title compound was prepared by the reaction of 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane with 4-chloro-2-methyl-phenoxyacetic acid in a ratio of 1:2. The structure has been proved by the data of elemental analysis, IR spectroscopy, NMR ((1)H, (13)C) technique and by X-ray diffraction analysis. Intermolecular hydrogen bonds between the azonium protons and oxygen atoms of the carboxylate groups were found. Immunoactive properties of the title compound have been screened. The compound has the ability to suppress spontaneous and Con A-stimulated cell proliferation in vitro and therefore can be considered as immunodepressant. Y1 - 2011 U6 - https://doi.org/10.1186/1752-153X-5-23 SN - 1752-153X VL - 5 IS - 17 PB - BioMed Central CY - London ER - TY - JOUR A1 - Adebayo, Segun Emmanuel A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Reich, Oliver A1 - Regen, Christian A1 - Münzberg, Marvin A1 - Abdan, Khalina A1 - Hanafi, Marsyita A1 - Zude-Sasse, Manuela T1 - Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear JF - Postharvest Biology and Technology N2 - Quality attributes of fruit determine its acceptability by the retailer and consumer. The objective of this work was to investigate the potential of absorption (μa) and reduced scattering (μs’) coefficients of European pear to analyze its fruit flesh firmness and soluble solids content (SSC). The absolute reference values, μa* (cm−1) and μs’* (cm−1), of pear were invasively measured, employing multi-spectral photon density wave (PDW) spectroscopy at preselected wavelengths of 515, 690, and 940 nm considering two batches of unripe and overripe fruit. On eight measuring dates during fruit development, μa and μs’ were analyzed non-destructively by means of laser light backscattering imaging (LLBI) at similar wavelengths of 532, 660, and 830 nm by means of fitting according to Farrell’s diffusion theory, using fix reference values of either μa* or μs’*. Both, the μa* and the μa as well as μs’* and μs’ showed similar trends. Considering the non-destructively measured data during fruit development, μa at 660 nm decreased 91 till 141 days after full bloom (dafb) from 1.49 cm−1 to 0.74 cm−1 due to chlorophyll degradation. At 830 nm, μa only slightly decreased from 0.41 cm−1 to 0.35 cm−1. The μs’ at all wavelengths revealed a decreasing trend as the fruit developed. The difference measured at 532 nm was most pronounced decreasing from 24 cm−1 to 10 cm−1, while at 660 nm and 830 nm values decreased from 15 cm−1 to 13 cm−1 and from 10 cm−1 to 8 cm−1, respectively. When building calibration models with partial least-squares regression analysis on the optical properties for non-destructive analysis of the fruit SSC, μa at 532 nm and 830 nm resulted in a correlation coefficient of R = 0.66, however, showing high measuring uncertainty. The combination of all three wavelengths gave an enhanced, encouraging R = 0.89 for firmness analysis using μs’ in the freshly picked fruit. KW - Absorption KW - Non-destructive KW - Pear KW - Quality KW - Scattering Y1 - 2017 U6 - https://doi.org/10.1016/j.postharvbio.2017.04.004 SN - 0925-5214 SN - 1873-2356 VL - 130 SP - 56 EP - 63 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Bivigou Koumba, Achille Mayelle A1 - Miasnikova, Anna A1 - Busch, Peter A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Polystyrene-block-poly (methoxy diethylene glycol acrylate)-block-polystyrene triblock copolymers in aqueous solution-a SANS study of the temperature-induced switching behavior JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - A concentrated solution of a symmetric triblock copolymer with a thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) middle block and short hydrophobic, fully deuterated polystyrene end blocks is investigated in D2O where it undergoes a lower critical solution temperature-type phase transition at ca. 36 A degrees C. Small-angle neutron scattering (SANS) in a wide temperature range (15-50 A degrees C) is used to characterize the size and inner structure of the micelles as well as the correlation between the micelles and the formation of aggregates by the micelles above the cloud point (CP). A model featuring spherical core-shell micelles, which are correlated by a hard-sphere potential or a sticky hard-sphere potential together with a Guinier form factor describing aggregates formed by the micelles above the CP, fits the SANS curves well in the entire temperature range. The thickness of the thermoresponsive micellar PMDEGA shell as well as the hard-sphere radius increase slightly already below the cloud point. Whereas the thickness of the thermoresponsive micellar shell hardly shrinks when heating through the CP and up to 50 A degrees C, the hard-sphere radius decreases within 3.5 K at the CP. The volume fraction decreases already significantly below the CP, which may be at the origin of the previously observed gel-sol transition far below the CP (Miasnikova et al., Langmuir 28: 4479-4490, 2012). Above the CP, small, and at higher temperatures, large aggregates are formed by the micelles. KW - Hydrogel KW - Thermoresponsive KW - LCST behavior KW - SANS Y1 - 2015 U6 - https://doi.org/10.1007/s00396-015-3535-6 SN - 0303-402X SN - 1435-1536 VL - 293 IS - 5 SP - 1515 EP - 1523 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Grillo, Isabelle A1 - Kulkarni, Amit A1 - Sharp, Melissa A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of aggregation in micellar solutions of thermoresponsive triblock copolymers - influence of concentration, start and target temperatures JF - Soft matter N2 - In aqueous solution, symmetric triblock copolymers with a thermoresponsive middle block and hydrophobic end blocks form flower-like core-shell micelles which collapse and aggregate upon heating through the cloud point (CP). The collapse of the micellar shell and the intermicellar aggregation are followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while heating micellar solutions of a poly((styrene-d(8))-b-(N-isopropyl acrylamide)-b-(styrene-d(8))) triblock copolymer in D2O rapidly through their CP. The influence of polymer concentration as well as of the start and target temperatures is addressed. In all cases, the micellar collapse is very fast. The collapsed micelles immediately form small clusters which contain voids. They densify which slows down or even stops their growth. For low concentrations and target temperatures just above the CP, i.e. shallow temperature jumps, the subsequent growth of the clusters is described by diffusion-limited aggregation. In contrast, for higher concentrations and/or higher target temperatures, i.e. deep temperature jumps, intermicellar bridges dominate the growth. Eventually, in all cases, the clusters coagulate which results in macroscopic phase separation. For shallow temperature jumps, the cluster surfaces stay rough; whereas for deep temperature jumps, a concentration gradient develops at late stages. These results are important for the development of conditions for thermal switching in applications, e.g. for the use of thermoresponsive micellar systems for transport and delivery purposes. Y1 - 2013 U6 - https://doi.org/10.1039/c2sm27152d SN - 1744-683X VL - 9 IS - 5 SP - 1685 EP - 1699 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Kulkarni, Amit A1 - Jain, Abhinav A1 - Wang, Weinan A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Pipich, Vitaliy A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response N2 - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902714p SN - 0024-9297 ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Meier-Koll, Andreas A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition and the segmental dynamics in concentrated micellar solutions of P(S-b-NIPAM) diblock copolymers JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We investigate concentrated solutions of poly(styrene-b-N-isopropyl acrylamide) (P(S-b-NIPAM)) diblock copolymers in deuterated water (D2O). Both structural changes and the changes of the segmental dynamics occurring upon heating through the lower critical solution temperature (LCST) of PNIPAM are studied using small-angle neutron scattering and neutron spin-echo spectroscopy. The collapse of the micellar shell and the cluster formation of collapsed micelles at the LCST as well as an increase of the segmental diffusion coefficient after crossing the LCST are detected. Comparing to our recent results on a triblock copolymer P(S-b-NIPAM-b-S) [25], we observe that the collapse transition of P(S-b-NIPAM) is more complex and that the PNIPAM segmental dynamics are faster than in P(S-b-NIPAM-b-S). KW - Block copolymers KW - Responsive polymers KW - Small-angle neutron scattering KW - Neutron spin-echo spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2382-3 SN - 0303-402X VL - 289 IS - 5-6 SP - 711 EP - 720 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Metwalli, Ezzeldin A1 - Diethert, Alexander A1 - Grillo, Isabelle A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump JF - Macromolecular rapid communications N2 - Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems. KW - polymer physics KW - thermoresponsive polymers KW - small-angle neutron scattering KW - time-resolved measurements Y1 - 2012 U6 - https://doi.org/10.1002/marc.201100631 SN - 1022-1336 VL - 33 IS - 3 SP - 254 EP - 259 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Adem, Fozia A. A1 - Mbaveng, Armelle T. A1 - Kuete, Victor A1 - Heydenreich, Matthias A1 - Ndakala, Albert A1 - Irungu, Beatrice A1 - Yenesew, Abiy A1 - Efferth, Thomas T1 - Cytotoxicity of isoflavones and biflavonoids from Ormocarpum kirkii towards multi-factorial drug resistant cancer JF - Phytomedicine : international journal of phytotherapy and phytopharmacology N2 - Background: While incidences of cancer are continuously increasing, drug resistance of malignant cells is observed towards almost all pharmaceuticals. Several isoflavonoids and flavonoids are known for their cytotoxicity towards various cancer cells. Methods: The cytotoxicity of compounds was determined based on the resazurin reduction assay. Caspases activation was evaluated using the caspase-Glo assay. Flow cytometry was used to analyze the cell cycle (propodium iodide (PI) staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP) (JC-1) and reactive oxygen species (ROS) (H2DCFH-DA). CCRF-CEM leukemia cells were used as model cells for mechanistic studies. Results: Compounds 1, 2 and 4 displayed IC50 values below 20 mu M towards CCRF-CEM and CEM/ADR5000 leukemia cells, and were further tested towards a panel of 7 carcinoma cells. The IC50 values of the compounds against carcinoma cells varied from 16.90 mu M (in resistant U87MG.Delta EGFR glioblastoma cells) to 48.67 mu M (against HepG2 hepatocarcinoma cells) for 1, from 7.85 mu M (in U87MG.Delta EGFR cells) to 14.44 mu M (in resistant MDA-MB231/BCRP breast adenocarcinoma cells) for 2, from 4.96 mu M (towards U87MG.Delta EGFRcells) to 7.76 mu M (against MDA-MB231/BCRP cells) for 4, and from 0.07 mu M (against MDA-MB231 cells) to 2.15 mu M (against HepG2 cells) for doxorubicin. Compounds 2 and 4 induced apoptosis in CCRF-CEM cells mediated by MMP alteration and increased ROS production. Conclusion: The present report indicates that isoflavones and biflavonoids from Ormocarpum kirkii are cytotoxic compounds with the potential of being exploited in cancer chemotherapy. Compounds 2 and 4 deserve further studies to develop new anticancer drugs to fight sensitive and resistant cancer cell lines. KW - Apoptosis KW - Cancer KW - Ormocarpum kirkii KW - Isoflavone KW - Biflavonoid KW - Multi-drug resistance Y1 - 2019 U6 - https://doi.org/10.1016/j.phymed.2019.152853 SN - 0944-7113 SN - 1618-095X VL - 58 PB - Elsevier CY - München ER - TY - JOUR A1 - Ahnert, Karsten A1 - Abel, Markus A1 - Kollosche, Matthias A1 - Jorgensen, Per Jorgen A1 - Kofod, Guggi T1 - Soft capacitors for wave energy harvesting JF - Journal of materials chemistry N2 - Wave energy harvesting could be a substantial renewable energy source without impact on the global climate and ecology, yet practical attempts have struggled with the problems of wear and catastrophic failure. An innovative technology for ocean wave energy harvesting was recently proposed, based on the use of soft capacitors. This study presents a realistic theoretical and numerical model for the quantitative characterization of this harvesting method. Parameter regions with optimal behavior are found, and novel material descriptors are determined, which dramatically simplify analysis. The characteristics of currently available materials are evaluated, and found to merit a very conservative estimate of 10 years for raw material cost recovery. Y1 - 2011 U6 - https://doi.org/10.1039/c1jm12454d SN - 0959-9428 SN - 1364-5501 VL - 21 IS - 38 SP - 14492 EP - 14497 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Akampurira, Denis A1 - Akala, Hoseah M. A1 - Derese, Solomon A1 - Heydenreich, Matthias A1 - Yenesew, Abiy T1 - A new C-C linked benzophenathridine-2-quinoline dimer, and the antiplasmodial activity of alkaloids from Zanthoxylum holstzianum JF - Natural product research N2 - The CH2Cl2/MeOH (1:1) extract of Zanthoxylum holstzianum stem bark showed good antiplasmodial activity (IC50 2.5 +/- 0.3 and 2.6 +/- 0.3 mu g/mL against the W2 and D6 strains of Plasmodium falciparum, respectively). From the extract five benzophenanthridine alkaloids [8-acetonyldihydrochelerythrine (1), nitidine (2), dihydrochelerythine (3), norchelerythrine (5), arnottianamide (8)]; a 2-quinolone alkaloid [N-methylflindersine (4)]; a lignan [4,4 '-dihydroxy-3,3 '-dimethoxylignan-9,9 '-diyl diacetate (7)] and a dimer of a benzophenanthridine and 2-quinoline [holstzianoquinoline (6)] were isolated. The CH2Cl2/MeOH (1:1) extract of the root bark afforded 1, 3-6, 8, chelerythridimerine (9) and 9-demethyloxychelerythrine (10). Holstzianoquinoline (6) is new, and is the second dimer linked by a C-C bond of a benzophenanthridine and a 2-quinoline reported thus far. The compounds were identified based on spectroscopic evidence. Amongst five compounds (1-5) tested against two strains of P. falciparum, nitidine (IC50 0.11 +/- 0.01 mu g/mL against W2 and D6 strains) and norchelerythrine (IC50 value of 0.15 +/- 0.01 mu g/mL against D6 strain) were the most active. KW - Antiplasmodial KW - benzophenanthridine alkaloid KW - holstzianoquinoline; KW - rutaceae KW - Zanthoxylum holstzianum Y1 - 2022 U6 - https://doi.org/10.1080/14786419.2022.2034810 SN - 1478-6419 SN - 1478-6427 VL - 37 IS - 13 SP - 2161 EP - 2171 PB - Taylor & Francis CY - London [u.a.] ER - TY - JOUR A1 - Akarsu, Pinar A1 - Grobe, Richard A1 - Nowaczyk, Julius A1 - Hartlieb, Matthias A1 - Reinicke, Stefan A1 - Böker, Alexander A1 - Sperling, Marcel A1 - Reifarth, Martin T1 - Solid-phase microcontact printing for precise patterning of rough surfaces BT - using polymer-tethered elastomeric stamps for the transfer of reactive silanes JF - ACS applied polymer materials N2 - We present a microcontact printing (mu CP) routine suitable to introduce defined (sub-) microscale patterns on surface substrates exhibiting a high capillary activity and receptive to a silane-based chemistry. This is achieved by transferring functional trivalent alkoxysilanes, such as (3-aminopropyl)-triethoxysilane (APTES) as a low-molecular weight ink via reversible covalent attachment to polymer brushes grafted from elastomeric polydimethylsiloxane (PDMS) stamps. The brushes consist of poly{N-[tris(hydroxymethyl)-methyl]acrylamide} (PTrisAAm) synthesized by reversible addition-fragmentation chain-transfer (RAFT)-polymerization and used for immobilization of the alkoxysilane-based ink by substituting the alkoxy moieties with polymer-bound hydroxyl groups. Upon physical contact of the silane-carrying polymers with surfaces, the conjugated silane transfers to the substrate, thus completely suppressing ink-flow and, in turn, maximizing printing accuracy even for otherwise not addressable substrate topographies. We provide a concisely conducted investigation on polymer brush formation using atomic force microscopy (AFM) and ellipsometry as well as ink immobilization utilizing two-dimensional proton nuclear Overhauser enhancement spectroscopy (H-1-H-1-NOESY-NMR). We analyze the mu CP process by printing onto Si-wafers and show how even distinctively rough surfaces can be addressed, which otherwise represent particularly challenging substrates. KW - microcontact printing KW - capillary-active substrates KW - silane chemistry KW - PDMS surface grafting KW - surface patterning KW - shuttled RAFT-polymerization Y1 - 2021 U6 - https://doi.org/10.1021/acsapm.1c00024 SN - 2637-6105 VL - 3 IS - 5 SP - 2420 EP - 2431 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Al Nakeeb, Noah A1 - Kochovski, Zdravko A1 - Li, Tingting A1 - Zhang, Youjia A1 - Lu, Yan A1 - Schmidt, Bernhard V. K. J. T1 - Poly(ethylene glycol) brush-b-poly(N-vinylpyrrolidone)-based double hydrophilic block copolymer particles crosslinked via crystalline alpha-cyclodextrin domains JF - RSC Advances N2 - Self-assembly of block copolymers is a significant area of polymer science. The self-assembly of completely water-soluble block copolymers is of particular interest, albeit a challenging task. In the present work the self-assembly of a linear-brush architecture block copolymer, namely poly(N-vinylpyrrolidone)-b-poly(oligoethylene glycol methacrylate) (PVP-b-POEGMA), in water is studied. Moreover, the assembled structures are crosslinked via alpha-CD host/guest complexation in a supramolecular way. The crosslinking shifts the equilibrium toward aggregate formation without switching off the dynamic equilibrium of double hydrophilic block copolymer (DHBC). As a consequence, the self-assembly efficiency is improved without extinguishing the unique DHBC self-assembly behavior. In addition, decrosslinking could be induced without a change in concentration by adding a competing complexation agent for alpha-CD. The self-assembly behavior was followed by DLS measurement, while the presence of the particles could be observed via cryo-TEM before and after crosslinking. Y1 - 2019 U6 - https://doi.org/10.1039/c8ra10672j SN - 2046-2069 VL - 9 IS - 9 SP - 4993 EP - 5001 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Al-Naji, Majd A1 - Schlaad, Helmut A1 - Antonietti, Markus T1 - New (and old) monomers from biorefineries to make polymer chemistry more sustainable JF - Macromolecular rapid communications N2 - This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers. KW - biodegradable polymers KW - biorefineries KW - carbohydrate‐ based KW - monomers KW - green polymers KW - lignocellulosic biomass Y1 - 2020 U6 - https://doi.org/10.1002/marc.202000485 SN - 1022-1336 SN - 1521-3927 VL - 42 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Alarcon, Julio A1 - Alderete, Joel B. A1 - Aguila, Sergio A1 - Peter, Martin G. T1 - Regio and stereoselective hydroxylation of alpha-agarofuran by biotransformation of rhizopus nigricans N2 - A new synthesis of 9 alpha-hydroxy-alpha-agarofuran (6 alpha) is described, using a microbiological hydroxylation alpha-agarofuran (5) as the key reaction. The stereochemistry of the biohydroxylation was determined on the basis of a NOESY-experiment and GIAO calculations at the B3LYP/cc-pVDZ level. A strong gamma-effect was observed at C15 of the agarofuran ring which was correctly predicted by the GIAO-B3LYP calculations Y1 - 2005 ER - TY - JOUR A1 - Alarcon, Julio A1 - Alderete, Joel B. A1 - Peter, Martin G. A1 - Becerra, Juan J. A1 - Silva, M. T1 - Study on synthesis of 3 alpha,4 alpha-dihydroxy-dihydro-beta-agarofuran Y1 - 1998 ER - TY - JOUR A1 - Ali, Mostafa A1 - Homann, Thomas A1 - Khalil, Mahmoud A1 - Kruse, Hans-Peter A1 - Rawel, Harshadrai Manilal T1 - Milk whey protein modification by coffee-specific phenolics effect on structural and functional properties JF - Journal of agricultural and food chemistry : a publication of the American Chemical Society N2 - A suitable vehicle for integration of bioactive plant constituents is proposed. It involves modification of proteins using phenolics and applying these for protection of labile constituents. It dissects the noncovalent and covalent interactions of beta-lactoglobulin with coffee-specific phenolics. Alkaline and polyphenol oxidase modulated covalent reactions were compared. Tryptic digestion combined with MALDI-TOF-MS provided tentative allocation of the modification type and site in the protein, and an in silico modeling of modified beta-lactoglobulin is proposed. The modification delivers proteins with enhanced antioxidative properties. Changed structural properties and differences in solubility, surface hydrophobicity, and emulsification were observed. The polyphenol oxidase modulated reaction provides a modified beta-lactoglobulin with a high antioxidative power, is thermally more stable, requires less energy to unfold, and, when emulsified with lutein esters, exhibits their higher stability against UV light. Thus, adaptation of this modification provides an innovative approach for functionalizing proteins and their uses in the food industry. KW - coffee phenolic compounds KW - whey proteins KW - antioxidants KW - protein-phenol interactions KW - modeling KW - functionalizing proteins Y1 - 2013 U6 - https://doi.org/10.1021/jf402221m SN - 0021-8561 VL - 61 IS - 28 SP - 6911 EP - 6920 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ali, Mostafa A1 - Homann, Thomas A1 - Kreisel, Janka A1 - Khalil, Mahmoud A1 - Puhlmann, Ralf A1 - Kruse, Hans-Peter A1 - Rawel, Harshadrai Manilal T1 - Characterization and modeling of the interactions between coffee storage proteins and phenolic compounds JF - Journal of agricultural and food chemistry : a publication of the American Chemical Society N2 - This study addresses the interactions of coffee storage proteins with coffee-specific phenolic compounds. Protein profiles, of Coffea arabica and Coffea canephora (var robusta) were compared. Major Phenolic compounds were extracted and analyzed with appropriate methods. The polyphenol-protein interactions during protein extraction have been addressed by different analytical setups [reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Trolox equivalent antioxidant capacity (TEAC) assays], with focus directed toward identification of covalent adduct formation. The results indicate that C. arabica proteins are more susceptible to these interactions and the polyphenol oxidase activity seems to be a crucial factor for the formation of these addition products. A tentative allocation of the modification type and site in the protein has been attempted. Thus, the first available in silico modeling of modified coffee proteins is reported. The extent of these modifications may contribute to the structure and function of "coffee melanoidins" and are discussed in the context of coffee flavor formation. KW - Coffee beans KW - storage proteins KW - phenolic compounds KW - antioxidants KW - protein-phenol interactions KW - modeling Y1 - 2012 U6 - https://doi.org/10.1021/jf303372a SN - 0021-8561 VL - 60 IS - 46 SP - 11601 EP - 11608 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Aloni, Sapir Shekef A1 - Perovic, Milena A1 - Weitman, Michal A1 - Cohen, Reut A1 - Oschatz, Martin A1 - Mastai, Yitzhak T1 - Amino acid-based ionic liquids as precursors for the synthesis of chiral nanoporous carbons JF - Nanoscale Advances N2 - The synthesis of chiral nanoporous carbons based on chiral ionic liquids (CILs) of amino acids as precursors is described. Such unique precursors for the carbonization of CILs yield chiral carbonaceous materials with high surface area (approximate to 620 m(2) g(-1)). The enantioselectivities of the porous carbons are examined by advanced techniques such as selective adsorption of enantiomers using cyclic voltammetry, isothermal titration calorimetry, and mass spectrometry. These techniques demonstrate the chiral nature and high enantioselectivity of the chiral carbon materials. Overall, we believe that the novel approach presented here can contribute significantly to the development of new chiral carbon materials that will find important applications in chiral chemistry, such as in chiral catalysis and separation and in chiral sensors. From a scientific point of view, the approach and results reported here can significantly deepen our understanding of chirality at the nanoscale and of the structure and nature of chiral nonporous materials and surfaces. Y1 - 2019 U6 - https://doi.org/10.1039/c9na00520j SN - 2516-0230 VL - 1 IS - 12 SP - 4981 EP - 4988 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Alrefai, Anas A1 - Mondal, Suvendu Sekhar A1 - Wruck, Alexander A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Brandt, Philipp A1 - Janiak, Christoph A1 - Schoenfeld, Sophie A1 - Weber, Birgit A1 - Rybakowski, Lawrence A1 - Herrman, Carmen A1 - Brennenstuhl, Katlen A1 - Eidner, Sascha A1 - Kumke, Michael Uwe A1 - Behrens, Karsten A1 - Günter, Christina A1 - Müller, Holger A1 - Holdt, Hans-Jürgen T1 - Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties JF - Journal of Inclusion Phenomena and Macrocyclic Chemistry N2 - By varying reaction parameters for the syntheses of the hydrogen-bonded metal-imidazolate frameworks (HIF) HIF-1 and HIF-2 (featuring 14 Zn and 14 Co atoms, respectively) to increase their yields and crystallinity, we found that HIF-1 is generated in two different frameworks, named as HIF-1a and HIF-1b. HIF-1b is isostructural to HIF-2. We determined the gas sorption and magnetic properties of HIF-2. In comparison to HIF-1a (Brunauer-Emmett-Teller (BET) surface area of 471m(2) g(-1)), HIF-2 possesses overall very low gas sorption uptake capacities [BET(CO2) surface area=85m(2) g(-1)]. Variable temperature magnetic susceptibility measurement of HIF-2 showed antiferromagnetic exchange interactions between the cobalt(II) high-spin centres at lower temperature. Theoretical analysis by density functional theory confirmed this finding. The UV/Vis-reflection spectra of HIF-1 (mixture of HIF-1a and b), HIF-2 and HIF-3 (with 14 Cd atoms) were measured and showed a characteristic absorption band centered at 340nm, which was indicative for differences in the imidazolate framework. KW - Gas-sorption KW - Ligand design KW - Magnetic properties KW - Supramolecular chemistry KW - Solvothermal synthesis Y1 - 2019 U6 - https://doi.org/10.1007/s10847-019-00926-6 SN - 1388-3127 SN - 1573-1111 VL - 94 IS - 3-4 SP - 155 EP - 165 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Andayi, Andrew W. A1 - Yenesew, Abiy A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Gitu, Peter M. A1 - Jondiko, Ogoche J. I. A1 - Akala, Hoseah M. A1 - Liyala, Pamela A1 - Wangui, Julia A1 - Waters, Norman C. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Antiplasmodial flavonoids from Erythrina sacleuxii N2 - The acetone extracts of the root bark and stem bark of Erythrina sacleuxii showed antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the acetone extract of the root bark afforded a new isoflavone, 7-hydroxy-4 -methoxy-3'- prenylisoflavone (trivial name 5-deoxy-3' - prenylbiochanin A) along with known isoflavonoids as the antiplasmodial principles. Flavonoids and isoflavonoids isolated from the stem bark of E. sucleuxii were also tested and showed antiplasmodial activities. The structures were determined on the basis of spectroscopic evidence Y1 - 2006 UR - http://www.thieme-connect.com/ejournals/toc/plantamedica U6 - https://doi.org/10.1055/s-2005-873200 SN - 0032-0943 ER - TY - JOUR A1 - Andersen, S. O. A1 - Peter, Martin G. A1 - Roepstorff, Peter T1 - Cuticular sclerotization in insects Y1 - 1996 ER - TY - JOUR A1 - Andrews, N. L. P. A1 - Ferguson, T. A1 - Rangaswamy, A. M. M. A1 - Bernicky, A. R. A1 - Henning, N. A1 - Dudelzak, A. A1 - Reich, Oliver A1 - Barnes, Jack A. A1 - Loock, Hans-Peter T1 - Hadamard-Transform Fluorescence Excitation-Emission-Matrix Spectroscopy JF - Analytical chemistry N2 - We present a fluorescence excitation-emission-matrix spectrometer with superior data acquisition rates over previous instruments. Light from a white light emitting diode (LED) source is dispersed onto a digital micromirror array (DMA) and encoded using binary n-size Walsh functions ("barcodes"). The encoded excitation light is used to irradiate the liquid sample and its fluorescence is dispersed and detected using a conventional array spectrometer. After exposure to excitation light encoded in n different ways, the 2-dimensional excitation-emission-matrix (EEM) spectrum is obtained by inverse Hadamard transformation. Using this technique we examined the kinetics of the fluorescence of rhodamine B as a function of temperature and the acid-driven demetalation of chlorophyll into pheophytin-a. For these experiments, EEM spectra with 31 excitation channels and 2048 emission channels were recorded every 15 s. In total, data from over 3000 EEM spectra were included in this report. It is shown that the increase in data acquisition rate can be as high as [{n(n + 1)}/2]-fold over conventional EEM spectrometers. Spectral acquisition rates of more than two spectra per second were demonstrated. Y1 - 2017 U6 - https://doi.org/10.1021/acs.analchem.7b02400 SN - 0003-2700 SN - 1520-6882 VL - 89 SP - 8554 EP - 8564 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Andrews, Nicholas L. P. A1 - Ross, Rachel A1 - Munzke, Dorit A1 - van Hoorn, Camiel A1 - Brzezinski, Andrew A1 - Barnes, Jack A. A1 - Reich, Oliver A1 - Loock, Hans-Peter T1 - In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber JF - Optics express : the international electronic journal of optics N2 - We describe an in-fiber interferometer based on a gas-filled hollow-core photonic crystal fiber. Expressions for the sensitivity, figure of merit and refractive index resolution are derived, and values are experimentally measured and theoretically validated using mode field calculations. The refractive indices of nine monoatomic and molecular gases are measured with a resolution of delta(ns) < 10(-6). (C)2016 Optical Society of America Y1 - 2016 U6 - https://doi.org/10.1364/OE.24.014086 SN - 1094-4087 VL - 24 SP - 14086 EP - 14099 PB - Optical Society of America CY - Washington ER - TY - JOUR A1 - Andrianov, Ivan A1 - Saalfrank, Peter T1 - Free vibrational relaxation of H adsorbed on a Si(100) surface investigated with the multi-configurational time-dependent Hartree method JF - Chemical physics letters N2 - The results of a quantum-mechanical study of vibrational relaxation of hydrogen adsorbed on a Si(100) surface with the multi-configurational time-dependent Hartree (MCTDH) method are presented. A two-dimensional subsystem is coupled non-linearly to a bath of harmonic oscillators (phonons of the Si bulk), and the relaxation of subsystem vibrations proceeds primarily via a two-phonon process. Characteristic times of the system evolution agree well with our previous perturbation theory study. The vibrational population decay is non-exponential, exhibiting pronounced recurrences due to finite bath size. The dependence of the lifetimes of the vibrational levels on the bath size and on the coupling details is investigated. Y1 - 2006 U6 - https://doi.org/10.1016/j.cplett.2006.11.067 SN - 0009-2614 VL - 433 SP - 91 EP - 96 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, I. A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - The effect of humic acid on the formation and solubility of secondary solid phases (Nd(OH)CO3 and Sm(OH)CO3) JF - Radiochimica acta : international journal for chemical aspects of nuclear science and technology N2 - The formation of secondary Ln(III) solid phases (e.g. Nd(OH)CO3 and Sm(OH)CO3) has been studied as a function of the humic acid (HA) concentration in 0.1 M NaClO4 aqueous solution and their solubility has been investigated in the neutral pH range (6.5-8) under normal atmospheric conditions. Nd(III) and Sm(III) were selected as analogues for trivalent lanthanide and actinide ions. The solid phases under investigation have been prepared by alkaline precipitation and characterized by TGA, ATR-FTIR, XRD, TRLFS, DR-UV-Vis and Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicate that Nd(OH)CO3 and Sm(OH)CO3 are stable and remain the solubility limiting solid phases even in the presence of increased HA concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurs, the inorganic (Ln(OH)CO3) and the organic phase (HA), which is adsorbed on the particle surface of the former. Nevertheless, HA affects the particle size of the solid phases. Increasing HA concentration results in decreasing crystallite size of the Nd(OH)CO3 and increasing crystallite size of the Sm(OH)CO3 solid phase, and affects inversely the solubility of the solid phases. However, this impact on the solid phase properties is expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - Lanthanide ions KW - Humic acid KW - Solid phase KW - Solubility KW - Raman KW - TRLFS KW - DR-UV-Vis Y1 - 2011 U6 - https://doi.org/10.1524/ract.2011.1812 SN - 0033-8230 VL - 99 IS - 4 SP - 217 EP - 223 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, Ioannis A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3) JF - Journal of rare earths N2 - The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - lanthanide ions KW - humic acid KW - solid phase KW - solubility KW - Raman KW - TRLFS KW - DR-UV-Vis KW - rare earths Y1 - 2011 U6 - https://doi.org/10.1016/S1002-0721(10)60490-5 SN - 1002-0721 VL - 29 IS - 6 SP - 516 EP - 521 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Apitz, Sabine E. A1 - Bell, Elanor M. A1 - Damgaard, Lars A1 - Gilbert, Franck A1 - Glud, R A1 - Hall, P. O. J. A1 - Kershaw, P. J. A1 - Nickel, L A1 - Parker, R A1 - Rabouille, Christophe A1 - Shimmield, Grahamm A1 - Solan, Martin A1 - Soltwedel, Thomas A1 - Spagnoli, Federico A1 - Witte, Ursula T1 - Coastal Ocean Benthic Observatories (COBO) : integrated tools for the in situ observation and study of benthic ecosystem biogeochemical processes Y1 - 2005 ER - TY - JOUR A1 - Aravopoulou, Dionysia A1 - Kyriakos, Konstantinos A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Kyritsis, Apostolos T1 - Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The thermoresponsive behavior of two diblock copolymers PS-b-PNIPAM and PS-b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt % polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS-b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS-b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS-b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS-b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε′. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS-b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric “jump” experiments show that the kinetics of micellar aggregation in the PS-b-PMDEGA solution is slower than that in the PS-b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε′, is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcb.7b09647 SN - 1520-6106 VL - 122 IS - 9 SP - 2655 EP - 2668 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Arias, Hugo R. A1 - Feuerbach, Dominik A1 - Schmidt, Bernd A1 - Heydenreich, Matthias A1 - Paz, Cristian A1 - Ortells, Marcelo O. T1 - Drimane Sesquiterpenoids Noncompetitively Inhibit Human alpha 4 beta 2 Nicotinic Acetylcholine Receptors with Higher Potency Compared to Human alpha 3 beta 4 and alpha 7 Subtypes JF - Journal of natural products N2 - The drimane sesquiterpenoids drimenin, cinnamolide, dendocarbin A, and polygodial were purified from the Canelo tree (Drimys winteri) and chemically characterized by spectroscopic methods. The pharmacological activity of these natural compounds were determined on hα4β2, hα3β4, and hα7 nicotinic acetylcholine receptors (AChRs) by Ca2+ influx measurements. The results established that drimane sesquiterpenoids inhibit AChRs with the following selectivity: hα4β2 > hα3β4 > hα7. In the case of hα4β2 AChRs, the following potency rank order was determined (IC50’s in μM): drimenin (0.97 ± 0.35) > cinnamolide (1.57 ± 0.36) > polygodial (62.5 ± 19.9) ≫ dendocarbin A (no activity). To determine putative structural features underlying the differences in inhibitory potency at hα4β2 AChRs, additional structure–activity relationship and molecular docking experiments were performed. The Ca2+ influx and structural results supported a noncompetitive mechanism of inhibition, where drimenin interacted with luminal and nonluminal (TMD-β2 intrasubunit) sites. The structure–activity relationship results, i.e., the lower the ligand polarity, the higher the inhibitory potency, supported the nonluminal interaction. Ligand binding to both sites might inhibit the hα4β2 AChR by a cooperative mechanism, as shown experimentally (nH > 1). Drimenin could be used as a molecular scaffold for the development of more potent inhibitors with higher selectivity for the hα4β2 AChR. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jnatprod.7b00893 SN - 0163-3864 SN - 1520-6025 VL - 81 IS - 4 SP - 811 EP - 817 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Armin, Ardalan A1 - Durrant, James R. A1 - Shoaee, Safa T1 - Interplay Between Triplet-, Singlet-Charge Transfer States and Free Charge Carriers Defining Bimolecular Recombination Rate Constant of Organic Solar Cells JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Despite the myriad of organic donor:acceptor materials, only few systems have emerged in the life of organic solar cells to, exhibit considerable reduced bimolecular recombination, with respect to the random encounter rate given by the Langevin equation. Monte Carlo simulations have revealed that the rate constant of the formation of electron-hole bound states depends on the random encounter of opposite charges and is nearly given by the Langevin equation for the domain sizes relevant to efficient bulk heterojunction systems. Recently, three studies :suggested that charge transfer states dissociating much faster than their decay rate to the ground state, can result in reduced bimolecular recombination by lowering the recombination rate to the ground state as a loss pathway. A separate study identified another loss pathway and suggested that forbidden back electron transfer from triplet charge transfer states to triplet excitons is a key to achieving reduced recombination. Herein we further explain the reduced bimolecular recombination by investigating the limitations of these two proposals. By solving kinetic rate equations for a BHJ system with realistic rates, we show that both of these previously presented conditions must only be held at the same time fora system to exhibit non-Langevin behavior. We demonstrate that suppression of both of the parallel loss channels of singlet and triplet states can be achieved through increasing the dissociation rate of the charge transfer states; a crucial requirement to achieve a high charge carrier extraction efficiency. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcc.7b04825 SN - 1932-7447 VL - 121 SP - 13969 EP - 13976 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André T1 - Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity N2 - Water-soluble block copolymers were prepared from the non-ionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]-ammonio propane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermo- responsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0°C and 100°C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates can be prepared in water which switch reversibly, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus. Y1 - 2002 ER - TY - JOUR A1 - Arys, Xavier A1 - Fischer, Peter A1 - Jonas, Alain M. A1 - Koetse, Marc M. A1 - Legras, Roger A1 - Laschewsky, André A1 - Wischerhoff, Erik T1 - Ordered polyelectrolyte multilayers : rules governing layering in organic binary multilayers Y1 - 2003 ER - TY - JOUR A1 - Ast, Sandra A1 - Rutledge, Peter J. A1 - Todd, Matthew H. T1 - Reversing the triazole topology in a cyclam-triazole-dye ligand gives a 10-fold brighter signal response to Zn2+ in aqueous solution JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The fluorescence response of a set of cyclam-triazole-dye ligands is controlled by the appended dye, but simple reversal of the triazole topology affords a novel probe for Zn2+ with a longer fluorescence lifetime and higher fluorescence quantum yield upon Zn2+ binding ( = 2.0 ns, Phi(f) = 0.76). KW - Sensors KW - Zinc KW - Click chemistry KW - Fluorescence KW - Electrochemistry Y1 - 2012 U6 - https://doi.org/10.1002/ejic.201201072 SN - 1434-1948 IS - 34 SP - 5611 EP - 5615 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ast, Sandra A1 - Schwarze, Thomas A1 - Müller, Holger A1 - Sukhanov, Aleksey A1 - Michaelis, Stefanie A1 - Wegener, Joachim A1 - Wolfbeis, Otto S. A1 - Körzdörfer, Thomas A1 - Dürkop, Axel A1 - Holdt, Hans-Jürgen T1 - A highly K+-Selective Phenylaza-[18]crown-6-Lariat-Ether-Based Fluoroionophore and its application in the sensing of K+ Ions with an optical sensor film and in cells JF - Chemistry - a European journal N2 - Herein, we report the synthesis of two phenylaza-[18]crown-6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K+ ions under simulated physiological conditions. The presence of a 2-methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat-free phenylaza-[18] crown-6 ether analogues. Probe 1 shows a high K+/Na+ selectivity and a 2.5-fold fluorescence enhancement was observed in the presence of 100 mm K+ ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8% per 1 mm K+ within the range 1-10 mm K+. The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K+ ions on both the extracellular and intracellular levels. KW - crown compounds KW - fluorescence KW - gels KW - potassium KW - sensors Y1 - 2013 U6 - https://doi.org/10.1002/chem.201302350 SN - 0947-6539 SN - 1521-3765 VL - 19 IS - 44 SP - 14911 EP - 14917 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Atilaw, Yoseph A1 - Duffy, Sandra A1 - Heydenreich, Matthias A1 - Muiva-Mutisya, Lois A1 - Avery, Vicky M. A1 - Erdelyi, Mate A1 - Yenesew, Abiy T1 - Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata JF - Molecules N2 - In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4-ethoxy-3-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum. KW - Tephrosia aequilata KW - chalcone KW - retrochalcone KW - aequichalcone A KW - aequichalcone B KW - aequichalcone C KW - pterocarpene KW - antiplasmodial Y1 - 2017 U6 - https://doi.org/10.3390/molecules22020318 SN - 1420-3049 VL - 22 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Atilaw, Yoseph A1 - Heydenreich, Matthias A1 - Ndakala, Albert A1 - Akala, Hoseah M. A1 - Kamau, Edwin A1 - Yenesew, Abiy T1 - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine: A new schizozygane indoline alkaloid from Schizozygia coffaeoides JF - Phytochemistry letters N2 - The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC50 = 8-12 mu g/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14 alpha, 15 alpha-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC50 = 13-52 mu m). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. KW - Schizozygia coffaeoides KW - Schizozygane indoline alkaloid KW - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine KW - Dimeric anthraquinone KW - Cassiamin A KW - Cassiamin B Y1 - 2014 U6 - https://doi.org/10.1016/j.phytol.2014.07.003 SN - 1874-3900 SN - 1876-7486 VL - 10 SP - 28 EP - 31 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Attenberger, Bianca A1 - Moussa, Mehdi El Sayed A1 - Brietzke, Thomas Martin A1 - Vreshch, Volodimir A1 - Holdt, Hans-Jürgen A1 - Lescop, Christophe A1 - Scheer, Manfred T1 - Discrete Polymetallic Arrangements of Ag-I and Cu-I Ions Based on Multiple Bridging Phosphane Ligands and pi-pi Interactions JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - A simple and straightforward approach to new polymetallic Ag-I and Cu-I supramolecules is presented. The reaction of N,P,N,P,N ligand 2 with Ag-I ions affords a trimetallic complex bearing a triangular Ag-3 core; metallophilic interactions are stabilized by ligands that display a multiple bridging coordination mode as 10-electron donors. Heteroleptic polymetallic Ag-I and Cu-I complexes based on ligand 2 and the 1,12-diazaperylene (dape) ligand are obtained by an alternative molecular organization of the polymetallic arrays compared to that in homoleptic complexes of ligand 2. KW - Heterocycles KW - N KW - P ligands KW - Pi interactions KW - Polyaromatic fragments KW - Supramolecular chemistry Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500445 SN - 1434-1948 SN - 1099-0682 IS - 18 SP - 2934 EP - 2938 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Conrad, Franziska A1 - Koch, Andreas A1 - Schilde, Uwe A1 - Poeppl, Andreas A1 - Strauch, Peter T1 - 1,10-phenanthroline-dithiolate mixed ligand transition metal complexes : synthesis, characterization and EPR spectroscopy N2 - A series of new N2S2 mixed ligand transition metal complexes, where N-2 is phenanthroline and S-2 is 1,2- dithiooxalate (dto) or 1,2-dithiosquarate (dtsq), has been synthesized and characterized. IR spectra reveal that the 1,2- dithiolate ligands are coordinated via the sulfur atoms forming a N2S2 coordination sphere. The copper(II) complex [Cu(phen)(dto)] was studied by EPR spectroscopy as a diamagnetically diluted powder. The diamagnetic dilution resulted from doping of the copper complex into the isostructural host lattice of the nickel complex [Ni(phen)(dto)]. The electronic situation in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of EHT and DFT calculations. Furthermore, one side product, chlorobis(1,10-phenanthroline)copper(I) ethanol solvate hydrate [(phen)(2)CuCl]center dot C2H5OH center dot H2O, was formed by a reduction process and characterized by X-ray diffraction. In the crystal packing one-dimensional columns of dimers are formed, stabilized by significant pi-pi interactions. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00201693 U6 - https://doi.org/10.1016/j.ica.2010.01.021 SN - 0020-1693 ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Koch, Andreas A1 - Mickler, Wulfhard A1 - Schilde, Uwe A1 - Strauch, Peter T1 - EPR spectroscopy of 4, 4 '-Bis(tert-butyl)-2, 2 '-bipyridine-1, 2-dithiolatocuprates(II) in host lattices with different coordination geometries JF - Zeitschrift für anorganische und allgemeine Chemie N2 - A series of new heteroleptic MN2S2 transition metal complexes with M = Cu2+ for EPR measurements and as diamagnetic hosts Ni2+, Zn2+, and Pd2+ were synthesized and characterized. The ligands are N2 = 4, 4'-bis(tert-butyl)-2, 2'-bipyridine (tBu2bpy) and S2 =1, 2-dithiooxalate, (dto), 1, 2-dithiosquarate, (dtsq), maleonitrile-1, 2-dithiolate, or 1, 2-dicyanoethene-1, 2-dithiolate, (mnt). The CuII complexes were studied by EPR in solution and as powders, diamagnetically diluted in the isostructural planar [NiII(tBu2bpy)(S2)] or[PdII(tBu2bpy)(S2)] as well as in tetrahedrally coordinated[ZnII(tBu2bpy)(S2)] host structures to put steric stress on the coordination geometry of the central CuN2S2 unit. The spin density contributions for different geometries calculated from experimental parameters are compared with the electronic situation in the frontier orbital, namely in the semi-occupied molecular orbital (SOMO) of the copper complex, derived from quantum chemical calculations on different levels (EHT and DFT). One of the hosts, [NiII(tBu2bpy)(mnt)], is characterized by X-ray structure analysis to prove the coordination geometry. The complex crystallizes in a square-planar coordination mode in the monoclinic space group P21/a with Z = 4 and the unit cell parameters a = 10.4508(10) angstrom, b = 18.266(2) angstrom, c = 12.6566(12) angstrom, beta = 112.095(7)degrees. Oxidation and reductions potentials of one of the host complexes, [Ni(tBu2bpy)(mnt)], were obtained by cyclovoltammetric measurements. KW - 1 KW - 2-Dithiosquarate KW - 1 KW - 2-Dithiooxalate KW - 1 KW - 2-Dicyanoethene-1 KW - 2-dithiolate KW - 4 KW - 4'-Bis(tert-butyl)-2 KW - 2'-bipyridine KW - X-ray structure KW - EPR KW - Copper KW - Nickel KW - Zinc Y1 - 2012 U6 - https://doi.org/10.1002/zaac.201100517 SN - 0044-2313 VL - 638 IS - 6 SP - 965 EP - 975 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Schilde, Uwe A1 - Strauch, Peter T1 - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridinedichlorometal(II) - Synthesis, structure and EPR spectroscopy JF - Inorganica chimica acta : the international inorganic chemistry journal N2 - Due to the better solubility of the 4,4'-substituted bipyridine ligand a series of 4,4'0-bis(tert-butyl)-2,2'-bipyridinedichlorometal(II) complexes, [M(tbbpy)Cl(2)], with M = Cu, Ni, Zn, Pd, Pt was synthesised and characterised. The blue copper complex 4,4'-bis(tert-butyl)-2,2'-bipyridinedichlorocopper(II) was isolated in two different polymorphic forms, as prisms 1 with a solvent inclusion and solvent-free as needles 2. Both structures were determined by X-ray structure analysis. They crystallise in the monoclinic space group P2(1)/c with four molecules in the unit cell, but with different unit cells and packing motifs. Whereas in the prisms 1, with the unit cell parameters a = 12.1613(12), b = 10.6363(7), c = 16.3074(15) angstrom, eta = 94.446(8)degrees, the packing is dominated by intra-and intermolecular hydrogen bonds, in the needles 2, with a = 7.738(1), b = 18. 333(2), c = 13.291(3) angstrom, beta = 97.512(15)degrees, only intramolecular hydrogen bonds appear and the complex molecules are arranged in columns which are stabilised by p-p-stacking interactions. In both complexes the copper has a tetrahedrally distorted coordination sphere. These copper complexes were also studied by EPR spectroscopy in solution, as frozen glass and diamagnetically diluted powder with the analogue [Pd(tbbpy)Cl(2)] as host lattice. KW - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridine KW - X-ray structure KW - EPR KW - Copper(II) KW - Transition metals Y1 - 2011 U6 - https://doi.org/10.1016/j.ica.2010.08.035 SN - 0020-1693 VL - 365 IS - 1 SP - 127 EP - 132 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Awasthi, Neha A1 - Ritschel, Thomas A1 - Lipowsky, Reinhard A1 - Knecht, Volker T1 - Standard gibbs energies of formation and equilibrium constants from ab-initio calculations covalent dimerization of NO2 and synthesis of NH3 JF - The journal of chemical thermodynamics N2 - Standard quantum chemical methods are used for accurate calculation of thermochemical properties such as enthalpies of formation, entropies and Gibbs energies of formation. Equilibrium reactions are widely investigated and experimental measurements often lead to a range of reaction Gibbs energies and equilibrium constants. It is useful to calculate these equilibrium properties from quantum chemical methods in order to address the experimental differences. Furthermore, most standard calculation methods differ in accuracy and feasibility of the system size. Hence, asystematic comparison of equilibrium properties calculated with different numerical algorithms would provide a useful reference. We select two well-known gas phase equilibrium reactions with small molecules: covalent dimer formation of NO2 (2NO(2) reversible arrow N2O4) and the synthesis of NH3 (N-2 + 3 H-2 reversible arrow 2NH(3)). We test four quantum chemical methods denoted by G3B3, CBS-APNO, W1 and CCSD(T) with aug-cc-pVXZ basis sets (X = 2, 3, and 4), to obtain thermochemical data for NO2, N2O4, and NH3. The calculated standard formation Gibbs energies Delta(f)G degrees are used to calculate standard reaction Gibbs energies Delta(r)G degrees and standard equilibrium constants K-eq for the two reactions. Standard formation enthalpies Delta H-f degrees are calculated in a more reliable way using high-level methods such as W1 and CCSD(T). Standard entropies S degrees for the molecules are calculated well within the range of experiments for all methods, however, the values of standard formation Gibbs energies Delta(f)G degrees show some dependence on the choice of the method. High-level methods perform better for the calculation of molecular energies, however, simpler methods such as G3B3 and CBS-APNO perform quite well in the calculation of total reaction energies and equilibrium constants, provided that the chemical species involved do not exhibit molecular geometries that are difficult to handle by the applied method. The temperature dependence of standard reaction Gibbs energy Delta(r)G degrees for the NH3 reaction is discussed by using the calculated standard formation Gibbs energies Delta(f)G degrees of the reaction species at 298.15 K. The corresponding equilibrium constant K-eq as a function of temperature is found to be close to experimental values. KW - Equilibrium constants KW - Thermochemical properties KW - Ab-initio calculations Y1 - 2013 U6 - https://doi.org/10.1016/j.jct.2013.03.011 SN - 0021-9614 VL - 62 IS - 3 SP - 211 EP - 221 PB - Elsevier CY - London ER - TY - JOUR A1 - Ayi, Ayi A. A1 - Khare, Varsha A1 - Strauch, Peter A1 - Girard, Jèrôme A1 - Fromm, Katharina M. A1 - Taubert, Andreas T1 - On the chemical synthesis of titanium nanoparticles from ionic liquids N2 - We report on attempts towards the synthesis of titanium nanoparticles using a wet chemical approach in imidazolium-based ionic liquids (ILs) under reducing conditions. Transmission electron microscopy finds nanoparticles in all cases. UV/Vis spectroscopy confirms the nanoparticulate nature of the precipitate, as in all cases an absorption band between ca. 280 and 300 nm is visible. IR spectroscopy shows that even after extensive washing and drying, some IL remains adsorbed on the nanoparticles. Raman spectroscopy suggests the formation of anatase nanoparticles, but X-ray diffraction reveals that, possibly, amorphous titania forms or that the nanoparticles are so small that a clear structure assignment is not possible. The report thus shows that (possibly amorphous) titanium oxides even form under reducing conditions and that the chemical synthesis of titanium nanoparticles in ILs remains elusive. Y1 - 2010 UR - http://www.springerlink.com/content/101572 U6 - https://doi.org/10.1007/s00706-010-0403-4 SN - 0026-9247 ER - TY - JOUR A1 - Bader, Denise A1 - Klier, Dennis Tobias A1 - Hettrich, C. A1 - Bier, Frank Fabian A1 - Wessig, Pablo T1 - Detecting carbohydrate-lectin interactions using a fluorescent probe based on DBD dyes JF - Analytical methods : advancing methods and applications N2 - Herein we present an efficient synthesis of a biomimetic probe with modular construction that can be specifically bound by the mannose binding FimH protein - a surface adhesion protein of E. coli bacteria. The synthesis combines the new and interesting DBD dye with the carbohydrate ligand mannose via a Click reaction. We demonstrate the binding to E. coli bacteria over a large concentration range and also present some special characteristics of those molecules that are of particular interest for the application as a biosensor. In particular, the mix-and-measure ability and the very good photo-stability should be highlighted here. Y1 - 2016 U6 - https://doi.org/10.1039/c5ay02991k SN - 1759-9660 SN - 1759-9679 VL - 8 SP - 1235 EP - 1238 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bagdahn, Christian A1 - Taubert, Andreas T1 - Ionogel fiber mats - functional materials via electrospinning of PMMA and the ionic liquid bis(1-butyl-3-methyl-imidazolium) Tetrachloridocuprate(II), [Bmim](2)[CuCl4] JF - Zeitschrift für Naturforschung : B, Chemical sciences N2 - Ionogel fiber mats were made by electrospinning poly(methylmethacrylate) (PMMA) and the ionic liquid (IL) bis(1-butyl-3-methyl-imidazolium) tetrachloridocupraten, [Bmim](2)[CuCl4], from acetone. The morphology of the electrospun ionogels strongly depends on the spinning parameters. Dense and uniform fiber mats were only obtained at concentrations of 60 to 70 g of polymer and IL mass combined. Lower concentrations led to a low number of poorly defined fibers. High voltages of 20 to 25 kV led to well-defined and uniform fibers; voltages between 15 and 20 kV again led to less uniform and less dense fibers. At 10 kV and lower, no spinning could be induced. Finally, PMMA fibers electrospun without IL show a less well-defined morphology combining fibers and oblong droplets indicating that the IL has a beneficial effect on the electrospinning process. The resulting materials are prototypes for new functional materials, for example in sterile filtration. KW - Ionic Liquid KW - Ionogel KW - Electrospinning KW - Fiber KW - Hydrogen Production KW - Filtration Y1 - 2013 U6 - https://doi.org/10.5560/ZNB.2013-3195 SN - 0932-0776 SN - 1865-7117 VL - 68 IS - 10 SP - 1163 EP - 1171 PB - De Gruyter CY - Tübingen ER - TY - JOUR A1 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Letzel, Matthias C. A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Sequence analysis of chitooligosaccharides by matrix-assisted laser desorption ionization postsource decay mass spectrometry N2 - Oligosaccharides composed of 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-D- glucopyranose (GlcN) were prepd. by chem. degrdn. of chitin or chitosan and sepd. by gel permeation chromatog. Oligosaccharides obtained after enzymic hydrolysis of chitosan [FA 0.19] with a fungal chitinase were derivatized by reductive amination with 2-aminoacridone and sequenced by matrix-assisted laser desorption ionization time-of-flight postsource decay (PSD) mass spectrometry (MS). The sequence of a trimer, D1A2, was established as D-A-A. The compn. of a hexamer D3A3 was .apprx.65% D-A-D-D-A-A and 35% D-D-A-D-A-A. The PSD MS of a nonamer D5A4-amac revealed four isobaric species D-X-Y-D-X-Y-D-A-A, where A is GlcNAc, D is GlcN, and X and Y (X ¹ Y) are mutually either D or A. This structure motif was also obsd. in a dodecamer D7A5 which was composed of eight isobaric sequences of the general formula (D-X-Y)3- D-A-A. Y1 - 2002 ER - TY - JOUR A1 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Peter-Katalinic, Jasna T1 - Characterization of chitooligosaccharides by mass spectrometry N2 - Heterochitooligosaccharides of DP 6, DP 9, and DP 12 were evaluated using established methods of derivatization and matrix-assisted laser desorption ionization post source decay mass spectrometry. Y1 - 2003 SN - 82-471-5901-5 ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Holdt, Hans-Jürgen T1 - PEPPSI-Effect on Suzuki-Miyaura Reactions Using 4,5-Dicyano-1,3-dimesitylimidazol-2-ylidene-Palladium Complexes: A Comparison between trans-Ligands JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl2{(CN)(2)IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN)(2)IMes ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes [PdCl2{(CN)(2)IMes}(PPh3)] (4) and [PdCl(dmba){(CN)(2)IMes}] (5) recently reported by our group in the Suzuki-Miyaura reaction of various aryl halides and phenylboronic acid. Reactions using previously reported [PdCl2(IMes)(py)] (IMes: 1,3-dimesitylimidazol-2-ylidene) (1) were also carried out and their results contrasted to those involving 12-15, 4 and 5. Differences in initiation rates and the catalytically active species related to the seven complexes in regards to the throw away ligand were investigated. Poisoning experiments with mercury show that palladium nanoparticles are responsible for the catalytic activity. KW - Carbene ligands KW - Palladium KW - Cross-coupling KW - Arenes Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500010 SN - 1434-1948 SN - 1099-0682 IS - 11 SP - 1950 EP - 1957 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Jackstell, Ralf A1 - Holdt, Hans-Jürgen T1 - Rhodium(I) and Silver(I) Complexes of 4,5-Dicyano-1,3-dimesityl- and 4,5-Dicyano-1,3-dineopentylimidazol-2-ylidene JF - Zeitschrift für anorganische und allgemeine Chemie N2 - The new N-heterocyclic carbene (NHC) precursors 4,5-dicyano-1, -dimesityl- (9) and 4, 5-dicyano-1, 3-dineopentyl-2-(pentafluorophenyl)imidazoline (14) were synthesized. 9 could be determined by X-ray crystallography. With the 2-pentafluorophenyl-substituted imidazolines 9 and 14, the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO)(2)(NHC)] complexes [NHC = 4, 5-dicyano-1, 3-dimesitylimidazol-2-ylidene (3) and 4, 5-dicyano-1, 3-dineopentylimidazol-2-ylidene (4)] were obtained. Crystal structures of [AgCl(3)] (15), [RhCl(COD)(3)] (17), [RhCl(COD)(4)] (18), and [RhCl(CO)(2)(3)] (19) were solved and with the crystal data of 19, the percent buried volume (%V-bur) of 31.8(+/- 0.1)% was determined for NHC 3. Infrared spectra of the imidazolines 9 and 14 and of the complexes 15-20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the 3 ( (-1)) and 4 ( (-1)), thus proving that 1, 3-substitution of maleonitrile-NHCs does not have a significant effect for the high -acceptor strength of these carbenes. KW - Carbenes KW - Rhodium KW - Silver KW - Crystal structure KW - Diaminomaleonitrile Y1 - 2013 U6 - https://doi.org/10.1002/zaac.201300250 SN - 0044-2313 SN - 1521-3749 VL - 639 IS - 10 SP - 1731 EP - 1739 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Holdt, Hans-Jürgen T1 - Investigation of the Catalytic Activity of a 2-Phenylidenepyridine Palladium(II) Complex Bearing 4,5-Dicyano-1,3-bis(mesityl)imidazol-2-ylidene in the Mizoroki-Heck Reaction JF - Zeitschrift für anorganische und allgemeine Chemie N2 - The phenylidenepyridine (ppy) palladacycles [PdCl(ppy)(IMes)] (4) [IMes = 1,3-bis(mesityl) imidazol-2-ylidene] and [PdCl(ppy){(CN)(2)IMes}] (6) [(CN)(2)IMes = 4,5-dicyano-1,3-bis(mesityl) imidazol-2-ylidene] were prepared by facile two step syntheses, starting with the reaction of palladium(II) chloride with 2-phenylpyridine followed by subsequent addition of the NHC ligand to the precatalyst precursor [PdCl(ppy)](2). Suitable crystals for the X-ray analysis of the complexes 4 and 6 were obtained. It was shown that 6 has a shorter NHC-palladium bond than the IMes complex 4. The difference of the palladium carbene bond lengths based on the higher pi-acceptor strength of (CN)(2)IMes in comparison to IMes. Thus, (CN)(2)IMes should stabilize the catalytically active central palladium atom better than IMes. As a measure for the pi-acceptor strength of (CN)(2)IMes compared to IMes, the selone (CN)(2)IMes center dot Se (7) was prepared and characterized by Se-77-NMR spectroscopy. The pi-acceptor strength of 7 was illuminated by the shift of its Se-77-NMR signal. The Se-77-NMR signal of 7 was shifted to much higher frequencies than the Se-77-NMR signal of IMes center dot Se. Catalytic experiments using the Mizoroki-Heck reaction of aryl chlorides with n-butyl acrylate showed that 6 is the superior performer in comparison to 4. Using complex 6, an extensive substrate screening of 26 different aryl bromides with n-butyl acrylate was performed. Complex 6 is a suitable precatalyst for para-substituted aryl bromides. The catalytically active species was identified by mercury poisoning experiments to be palladium nanoparticles. KW - Carbene ligands KW - Heck reaction KW - Palladium KW - Selenium KW - C-C coupling Y1 - 2016 U6 - https://doi.org/10.1002/zaac.201500625 SN - 0044-2313 SN - 1521-3749 VL - 642 SP - 140 EP - 147 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Metzner, Philipp A1 - Körzdörfer, Thomas A1 - Kelling, Alexandra A1 - Holdt, Hans-Jürgen T1 - Efficient palladium(II) precatalysts bearing 4,5-dicyanoimidazol-2-ylidene for the Mizoroki-Heck reaction JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The new N-heterocyclic carbene (NHC) complex [PdCl2{(CN)(2)IMes}(PPh3)] (2) ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) and the NHC palladacycle [PdCl(dmba){(CN)(2)IMes}] (3) (dmba: N,N-dimethylbenzylamine) have been synthesized by thermolysis of 4,5-dicyano-1,3-dimesityl-2-(pentafluorophenyl) imidazoline (1) in the presence of suitable palladium(II) precursors. The acyclic complex 2 was formed by ligand exchange using the mononuclear precursor [PdCl2(PPh3)(2)] and the palladacycle 3 was formed by cleavage of the dinuclear chloro-bridged precursor [Pd(mu-Cl)(dmba)](2). The new NHC precursor 1-benzyl-4,5-dicyano-2-(pentafluorophenyl)-3-picolylimidazoline (5) was formed by condensation of pentafluorobenzaldehyde with N-benzyl-N'-picolyldiaminomaleonitrile (4). The NHC palladacycle [PdCl2{(CN)(2)IBzPic}] (6) ({(CN)(2)IBzPic}: 1-benzyl-4,5-dicyano-3-picolylimidazol-2-ylidene) was prepared by in situ thermolysis of 5 in the presence of [PdCl2(PhCN)(2)]. The three palladium(II) complexes were characterized by NMR and IR spectroscopy, mass spectrometry and elemental analysis. In addition, the molecular structures of 2 and 3 were determined by X-ray diffraction. The pi-acidity of (CN)(2)IBzPic was compared with (CN)(2)IMes and perviously reported pi-acidic imidazol-2-ylidenes by NBO analysis. The Mizoroki-Heck (MH) reactions of various aryl halides with n-butyl acrylate were performed in the presence of complexes 2, 3 and 6. The new precatalysts showed high activity in the MH reactions giving good-to-excellent product yields with 0.1 mol-% pre-catalyst. The nature of the catalytically active species of 2, 3 and 6 was investigated by poisoning experiments with mercury and transmission electron microscopy. It was found that palladium nanoparticles formed from the precatalysts were involved in the catalytic process. KW - Homogeneous catalysis KW - Palladium KW - Cross coupling KW - Carbene ligands Y1 - 2014 U6 - https://doi.org/10.1002/ejic.201402040 SN - 1434-1948 SN - 1099-0682 IS - 18 SP - 2952 EP - 2960 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Balci, K. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Collier, W. B. A1 - Stricker, M. C. A1 - Stover, D. D. A1 - Ritzhaupt, G. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - The effects of conformation and zwitterionic tautomerism on the structural and vibrational spectral data of anserine JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - In this study, the stable conformers of neutral anserine were searched by molecular dynamics simulations and energy minimization calculations using the MM2 force field. Thermochemical calculations at B3LYP/6-31G(d) level of theory followed these preliminary calculations. The results confirmed that neutral anserine has quite a flexible structure and many stable gauche and trans conformers at room temperature. Nevertheless, two are considerably more favourable in energy than the others and expected to dominate the gas-phase and matrix IR spectra of the molecule. The corresponding structural and vibrational spectral data for these two conformers of neutral anserine, whose relative stabilities were also examined by high-accuracy energy calculations carried out using G3MP2B3 method, and for the most stable conformer of anserine in zwitterion form were calculated at B3LYP/6-311++G(d,p) level of theory. The calculated harmonic force constants were refined using the Scaled Quantum Mechanical Force Field (SQM-FF) method and then used to produce the refined wavenumbers, potential energy distributions (PEDs) and IR and Raman intensities. These refined data together with the scaled harmonic wavenumbers obtained using another method, Dual Scale factors (DS), enabled us to correctly analyse the observed IR and Raman spectra of anserine and revealed the effects of conformation and zwitterionic tautomerism on its structural and vibrational spectral data. (C) 2016 Elsevier B.V. All rights reserved. KW - Anserine KW - Matrix IR spectrum KW - Tautomerism KW - SQM-FF KW - Dual scale factors Y1 - 2016 U6 - https://doi.org/10.1016/j.vibspec.2016.08.003 SN - 0924-2031 SN - 1873-3697 VL - 86 SP - 277 EP - 289 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A theoretical IR spectroscopic study based on DFT calculations for free mn-15S(2)O(3) maleonitrile-dithiacrown ether compound N2 - The theoretically possible stable conformers of free mn-15S2O3 maleonitrile-dithiacrown ether molecule were searched by means of a conformational study which consists of molecular dynamics and energy minimization calculations performed with MM2 force field and successive geometry optimization + frequency calculations performed first at B3LYP/3- 21G and then at B3LYP/6-31G(d) levels of theory. The obtained calculation results have clearly indicated that the free molecule in electronic ground state is very flexible and accordingly has many possible stable conformers of different conformational properties at room temperature; among them, the one having a macrocyclic ring structure in which all of the ether units oriented toward the center of the ring was determined the energetically most preferable conformer. In addition, the equilibrium geometrical parameters, vibrational normal modes and associated IR spectral data of the determined most stable three conformers of the molecule were calculated at B3LYP/6-31+G(d) and B3LYP/6-31++G(d,p) levels of theory. A successful assignment of the fundamental bands observed in the recorded experimental solid phase and solution phase IR spectra of the molecule was achieved in the light of the theoretical data obtained from these DFT calculations. To fit the calculated harmonic wavenumbers to the experimental ones, two different scaling procedures, referred to as "Scaled Quantum Mechanical Force Field (SQM FF) methodology" and "Scaling wavenumbers with empirical dual scale factors", were proceeded independently. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2008.08.027 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations N2 - A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2005.10.048 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Yapar, G. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy)ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople-style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major contribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibrations to conformation, substitution and dimerization were discussed. KW - Glycol podands KW - Salicylic acid KW - IR and Raman spectra KW - SQM FF KW - Dual Scale Factors Y1 - 2012 U6 - https://doi.org/10.1016/j.vibspec.2011.11.011 SN - 0924-2031 VL - 58 IS - 1-2 SP - 27 EP - 43 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bald, Ilko A1 - Keller, Adrian A1 - Kopyra, Janina T1 - On the role of fluoro-substituted nucleosides in DNA radiosensitization for tumor radiation therapy JF - RSC Advances : an international journal to further the chemical sciences N2 - Gemcitabine (2′,2′-difluorocytidine) is a well-known radiosensitizer routinely applied in concomitant chemoradiotherapy. During irradiation of biological media with high-energy radiation secondary low-energy (<10 eV) electrons are produced that can directly induce chemical bond breakage in DNA by dissociative electron attachment (DEA). Here, we investigate and compare DEA to the three molecules 2′-deoxycytidine, 2′-deoxy-5-fluorocytidine, and gemcitabine. Fluorination at specific molecular sites, i.e., nucleobase or sugar moiety, is found to control electron attachment and subsequent dissociation pathways. The presence of two fluorine atoms at the sugar ring results in more efficient electron attachment to the sugar moiety and subsequent bond cleavage. For the formation of the dehydrogenated nucleobase anion, we obtain an enhancement factor of 2.8 upon fluorination of the sugar, whereas the enhancement factor is 5.5 when the nucleobase is fluorinated. The observed fragmentation reactions suggest enhanced DNA strand breakage induced by secondary electrons when gemcitabine is incorporated into DNA. KW - low-energy electrons KW - single-strand breaks KW - gas-phase KW - chemoradiation therapy KW - molecular-mechanisms KW - resonant formation KW - damage KW - attachment KW - drugs Y1 - 2014 U6 - https://doi.org/10.1039/C3RA46735J SN - 2046-2069 VL - 4 IS - 13 SP - 6825 EP - 6829 PB - Royal Society of Chemistry ER - TY - JOUR A1 - Bald, Ilko A1 - Schürmann, Robin Mathis A1 - Ebel, Kenny A1 - Nicolas, Christophe A1 - Milosavljevic, Aleksandar R. T1 - Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol JF - The Journal of Physical Chemistry Letters N2 - Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system. Y1 - 2019 UR - https://pubs.acs.org/doi/10.1021/acs.jpclett.9b00848 U6 - https://doi.org/10.1021/acs.jpclett.9b00848 SN - 1948-7185 VL - 10 SP - 3153 EP - 3158 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Bald, Ilko A1 - Solov'yov, Ilia A. A1 - Mason, Nigel J. A1 - Solov'yov, Andrey V. T1 - Special issue BT - dynamics of systems on the nanoscale (2018). Editorial JF - The European physical journal. D, Atomic, molecular, optical and plasma physics N2 - The structure, formation and dynamics of both animate and inanimate matter on the nanoscale are a highly interdisciplinary field of rapidly emerging research engaging a broad community encompassing experimentalists, theorists, and technologists. It is relevant for a large variety of molecular and nanosystems of different origin and composition and concerns numerous phenomena originating from physics, chemistry, biology, or materials science. This Topical Issue presents a collection of original research papers devoted to different aspects of structure and dynamics on the nanoscale. Some of the contributions discuss specific applications of the research results in several modern technologies and in next generation medicine. Most of the works of this topical issue were reported at the Fifth International Conference on Dynamics of Systems on the Nanoscale (DySoN) - the premier forum for the presentation of cutting-edge research in this field that was held in Potsdam, Germany in October of 2018. Y1 - 2020 U6 - https://doi.org/10.1140/epjd/e2020-10134-4 SN - 1434-6060 SN - 1434-6079 VL - 74 IS - 4 SP - 75 EP - 82 PB - Springer CY - Berlin ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Agarwal, Vivechana A1 - Pacholski, Claudia T1 - Fabrication of porous silicon-based optical sensors using metal-assisted chemical etching JF - RSC Advances N2 - Optical biosensors based on porous silicon were fabricated by metal assisted chemical etching. Thereby double layered porous silicon structures were obtained consisting of porous pillars with large pores on top of a porous silicon layer with smaller pores. These structures showed a similar sensing performance in comparison to electrochemically produced porous silicon interferometric sensors. Y1 - 2016 U6 - https://doi.org/10.1039/c5ra26816h SN - 2046-2069 VL - 6 SP - 21430 EP - 21434 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Antunez, E. E. A1 - Olive-Mendez, Sion Federico A1 - Pacholski, Claudia A1 - Campos-Alvarez, Jose A1 - Bokhimi, Xim A1 - Agarwal, V. T1 - Porous silicon pillar and bilayer structure as a nucleation center for the formation of aligned vanadium pentoxide nanorods JF - Ceramics International N2 - Porous silicon single layer (PSM), bilayer (PSB) and pillar (PSP) structures have been evaluated as nucleation centers for vanadium pentoxide (V2O5) crystals. Deposition of vanadium precursor over different substrates (drop casting technique), followed by annealing treatment under Ar-H-2 (5% H-2) atmosphere, induced crystallization of vanadium oxide. With respect to c-Si/SiO2 substrate, V2O5 nanorods with relatively large aspect ratio were formed over and within PSP structures. On the other hand, pores in PSM and PSB were found to be filled with relatively smaller crystals. Additionally, PSB provided a nucleation substrate capable to align the nanocrystals in a preferential orientation, while V2O5 crystals grown on PSP were found to be randomly aligned around the nanoporous pillar microstructure. Nanorods and nanocrystals were identified as V2O5 by temperature-controlled XRD measurements and evidence of their crystalline nature was observed via transmission electron microscopy. A careful analysis of electronic microscopy images allows the identification of the facets composing the ends of the crystals and its corresponding surface free energy has been evaluated employing the Wulff theorem. Such high surface area composite structures have potential applications as cathode material in Lithium-ion batteries. KW - Porous silicon KW - Vanadium pentoxide KW - Nanorods KW - Crystallization KW - Nanostructures Y1 - 2017 U6 - https://doi.org/10.1016/j.ceramint.2017.03.114 SN - 0272-8842 SN - 1873-3956 VL - 43 SP - 8023 EP - 8030 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Estevez-Espinoza, J. O. A1 - Salazar-Kuri, U. A1 - Pacholski, Claudia A1 - Mochan, Wolf Luis A1 - Agarwal, Vivechana T1 - Fabrication of ordered tubular porous silicon structures by colloidal lithography and metal assisted chemical etching BT - SERS performance of 2D porous silicon structures JF - Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces N2 - Fabrication of well-ordered porous silicon tubular structures using colloidal lithography and metal assisted chemical etching is reported. A continuous hexagonal hole/particle gold pattern was designed over monocrystalline silicon through deposition of polyNIPAM microspheres, followed by the surface decoration with gold nanoparticles and thermal treatment. An etching reaction with HF, ethanol and H2O2 dissolved the silicon in contact with the metal nanoparticles (NP), creating a porous tubular array in the "off-metal area". The morphological characterization revealed the formation of a cylindrical hollow porous tubular shape with external and internal diameter of approx. 900 nm and 400 nm respectively, though it can be tuned to other desired sizes by choosing an appropriate dimension for the microspheres. The porous morphology and optical properties were studied as a function of resistivity of silicon substrates. Compared to two different gold templates on cSi and nontubular porous pillar structures, porous silicon tubular framework revealed a maximum surface enhanced Raman scattering enhancement factor of 10(6) for the detection of 6-mercaptopurine (6-MP). Due to the large surface area available for any surface modification, open nanostructured platforms such as those studied here have potential applications in the field of reflection/photoluminescene and SERS based optical bio-/chemical sensors. KW - SERS KW - Porous silicon KW - MACE KW - Colloidal lithography KW - PolyNIPAM KW - 6-Mercaptopurine Y1 - 2018 U6 - https://doi.org/10.1016/j.apsusc.2018.08.120 SN - 0169-4332 SN - 1873-5584 VL - 462 SP - 783 EP - 790 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia T1 - Plasmonic Nanohole Arrays on Top of Porous Silicon Sensors BT - A Win-Win Situation JF - ACS applied materials & interfaces N2 - Label-free optical sensors are attractive candidates, for example, for detecting toxic substances and monitoring biomolecular interactions. Their performance can be pushed by the design of the sensor through clever material choices and integration of components. In this work, two porous materials, namely, porous silicon and plasmonic nanohole arrays, are combined in order to obtain increased sensitivity and dual-mode sensing capabilities. For this purpose, porous silicon monolayers are prepared by electrochemical etching and plasmonic nanohole arrays are obtained using a bottom-up strategy. Hybrid sensors of these two materials are realized by transferring the plasmonic nanohole array on top of the porous silicon. Reflectance spectra of the hybrid sensors are characterized by a fringe pattern resulting from the Fabry–Pérot interference at the porous silicon borders, which is overlaid with a broad dip based on surface plasmon resonance in the plasmonic nanohole array. In addition, the hybrid sensor shows a significant higher reflectance in comparison to the porous silicon monolayer. The sensitivities of the hybrid sensor to refractive index changes are separately determined for both components. A significant increase in sensitivity from 213 ± 12 to 386 ± 5 nm/RIU is determined for the transfer of the plasmonic nanohole array sensors from solid glass substrates to porous silicon monolayers. In contrast, the spectral position of the interference pattern of porous silicon monolayers in different media is not affected by the presence of the plasmonic nanohole array. However, the changes in fringe pattern reflectance of the hybrid sensor are increased 3.7-fold after being covered with plasmonic nanohole arrays and could be used for high-sensitivity sensing. Finally, the capability of the hybrid sensor for simultaneous and independent dual-mode sensing is demonstrated. KW - optical sensors KW - porous silicon KW - surface plasmon resonance KW - plasmonic KW - nanohole arrays KW - bottom-up fabrication Y1 - 2021 U6 - https://doi.org/10.1021/acsami.1c07034 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 30 SP - 36436 EP - 36444 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Schürmann, Robin Mathis A1 - Pacholski, Claudia T1 - One Spot-Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance JF - Frontiers in chemistry N2 - Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot. KW - porous silicon KW - interferometry KW - gold nanostructures KW - surface plasmon resonance KW - optical sensor Y1 - 2019 U6 - https://doi.org/10.3389/fchem.2019.00593 SN - 2296-2646 VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Balischewski, Christian A1 - Behrens, Karsten A1 - Zehbe, Kerstin A1 - Günter, Christina A1 - Mies, Stefan A1 - Sperlich, Eric A1 - Kelling, Alexandra A1 - Taubert, Andreas T1 - Ionic liquids with more than one metal BT - optical and rlectrochemical properties versus d-block metal vombinations JF - Chemistry - a European journal N2 - Thirteen N-butylpyridinium salts, including three monometallic [C4Py](2)[MCl4], nine bimetallic [C4Py](2)[(M1-xMxCl4)-M-a-Cl-b] and one trimetallic compound [C4Py](2)[(M1-y-zMyMz (c) Cl4)-M-a-M-b] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 degrees C. X-ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10(-4) and 10(-8) S cm(-1). Some Cu-based ILs reach conductivities of 10(-2) S cm(-1), which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47x10(-1) S cm(-1) at 70 degrees C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V. KW - bandgap KW - electrochemistry KW - ionic liquids KW - metal-containing ionic KW - liquids KW - tetrahalido metallates Y1 - 2020 U6 - https://doi.org/10.1002/chem.202003097 SN - 0947-6539 SN - 1521-3765 VL - 26 IS - 72 SP - 17504 EP - 17513 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Balischewski, Christian A1 - Bhattacharyya, Biswajit A1 - Sperlich, Eric A1 - Günter, Christina A1 - Beqiraj, Alkit A1 - Klamroth, Tillmann A1 - Behrens, Karsten A1 - Mies, Stefan A1 - Kelling, Alexandra A1 - Lubahn, Susanne A1 - Holtzheimer, Lea A1 - Nitschke, Anne A1 - Taubert, Andreas T1 - Tetrahalidometallate(II) ionic liquids with more than one metal BT - the effect of bromide versus chloride JF - Chemistry - a European journal N2 - Fifteen N-butylpyridinium salts - five monometallic [C4Py](2)[MBr4] and ten bimetallic [C4Py](2)[(M0.5M0.5Br4)-M-a-Br-b] (M=Co, Cu, Mn, Ni, Zn) - were synthesized, and their structures and thermal and electrochemical properties were studied. All the compounds are ionic liquids (ILs) with melting points between 64 and 101 degrees C. Powder and single-crystal X-ray diffraction show that all ILs are isostructural. The electrochemical stability windows of the ILs are between 2 and 3 V. The conductivities at room temperature are between 10(-5) and 10(-6) S cm(-1). At elevated temperatures, the conductivities reach up to 10(-4) S cm(-1) at 70 degrees C. The structures and properties of the current bromide-based ILs were also compared with those of previous examples using chloride ligands, which illustrated differences and similarities between the two groups of ILs. KW - electrochemistry KW - ionic liquids KW - metal-containing ionic liquids; KW - N-butylpyridinium bromide KW - tetrahalidometallates Y1 - 2022 U6 - https://doi.org/10.1002/chem.202201068 SN - 1521-3765 VL - 28 IS - 64 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Balischewski, Christian A1 - Choi, Hyung-Seok A1 - Behrens, Karsten A1 - Beqiraj, Alkit A1 - Körzdörfer, Thomas A1 - Gessner, Andre A1 - Wedel, Armin A1 - Taubert, Andreas T1 - Metal sulfide nanoparticle synthesis with ionic liquids state of the art and future perspectives JF - ChemistryOpen N2 - Metal sulfides are among the most promising materials for a wide variety of technologically relevant applications ranging from energy to environment and beyond. Incidentally, ionic liquids (ILs) have been among the top research subjects for the same applications and also for inorganic materials synthesis. As a result, the exploitation of the peculiar properties of ILs for metal sulfide synthesis could provide attractive new avenues for the generation of new, highly specific metal sulfides for numerous applications. This article therefore describes current developments in metal sulfide nano-particle synthesis as exemplified by a number of highlight examples. Moreover, the article demonstrates how ILs have been used in metal sulfide synthesis and discusses the benefits of using ILs over more traditional approaches. Finally, the article demonstrates some technological challenges and how ILs could be used to further advance the production and specific property engineering of metal sulfide nanomaterials, again based on a number of selected examples. KW - Ionic liquids KW - ionic liquid crystals KW - ionic liquid precursors KW - metal KW - sulfides KW - catalysis KW - electrochemistry KW - energy materials KW - LED KW - solar KW - cells Y1 - 2021 U6 - https://doi.org/10.1002/open.202000357 SN - 2191-1363 VL - 10 IS - 2 SP - 272 EP - 295 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Balk, Maria A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Quadruple-shape hydrogels JF - Smart materials and structures N2 - The capability of directed movements by two subsequent shape changes could be implemented in shape-memory hydrogels by incorporation of two types of crystallizable side chains While in non-swollen polymer networks even more directed movements could be realized, the creation of multi-shape hydrogels is still a challenge. We hypothesize that a quadruple-shape effect in hydrogels can be realized, when a swelling capacity almost independent of temperature is generated, whereby directed movements could be enabled, which are not related to swelling. In this case, entropy elastic recovery could be realized by hydrophilic segments and the fixation of different macroscopic shapes by means of three semi-crystalline side chains generating temporary crosslinks. Monomethacrylated semi-crystalline oligomers were connected as side chains in a hydrophilic polymer network via radical copolymerization. Computer assisted modelling was utilized to design a demonstrator capable of complex shape shifts by creating a casting mold via 3D printing from polyvinyl alcohol. The demonstrator was obtained after copolymerization of polymer network forming components within the mold, which was subsequently dissolved in water. A thermally-induced quadruple-shape effect was realized after equilibrium swelling of the polymer network in water. Three directed movements were successfully obtained when the temperature was continuously increased from 5 degrees C to 90 degrees C with a recovery ratio of the original shape above 90%. Hence, a thermally-induced quadruple-shape effect as new record for hydrogels was realized. Here, the temperature range for the multi-shape effect was limited by water as swelling media (0 degrees C-100 degrees C), simultaneously distinctly separated thermal transitions were required, and the overall elasticity indispensable for successive deformations was reduced as result of partially chain segment orientation induced by swelling in water. Conclusively the challenges for penta- or hexa-shape gels are the design of systems enabling higher elastic deformability and covering a larger temperature range by switching to a different solvent. KW - shape-memory KW - hydrogels KW - semi-crystalline Y1 - 2019 U6 - https://doi.org/10.1088/1361-665X/ab0e91 SN - 0964-1726 SN - 1361-665X VL - 28 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Balk, Maria A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Hydrolytic Degradation of Actuators Based on Copolymer Networks From Oligo(epsilon-caprolactone) Dimethacrylate and n-Butyl Acrylate JF - MRS advances N2 - Shape-memory polymer actuators often contain crystallizable polyester segments. Here, the influence of accelerated hydrolytic degradation on the actuation performance in copolymer networks based on oligo(epsilon-caprolactone) dimethacrylate (OCL) and n-butyl acrylate is studied The semi-crystalline OCL was utilized as crosslinker with molecular weights of 2.3 and 15.2 kg.mol(-1) (ratio: 1:1 wt%) and n-butyl acrylate (25 wt% relative to OCL content) acted as softening agent creating the polymer main chain segments within the network architecture. The copolymer networks were programmed by 50% elongation and were degraded by means of alkaline hydrolysis utilizing sodium hydroxide solution (pH = 13). Experiments were performed in the range of the broad melting range of the actuators at 40 degrees C. The degradation of test specimen was monitored by the sample mass, which was reduced by 25 wt% within 105 d .45 degradation products, fragments of OCL with molecular masses ranging from 400 to 50.000 g.mol(-1) could be detected by NMR spectroscopy and GPC measurements. The cleavage of ester groups included in OCL segments resulted in a decrease of the melting temperature (T-m) related to the actuator domains (amorphous at the temperature of degradation) and simultaneously, the T-m associated to the skeleton domain was increased (semi-crystalline at the temperature of degradation). The alkaline hydrolysis decreased the polymer chain orientation of OCL domains until a random alignment of crystalline domains was obtained. This result was confirmed by cyclic thermomechanical actuation tests. The performance of directed movements decreased almost linearly as function of degradation time resulting in the loss of functionality when the orientation of polymer chains disappeared. Here, actuators were able to provide reversible movements until 91 d when the accelerated bulk degradation procedure using alkaline hydrolysis (pH = 13) was applied. Accordingly, a lifetime of more than one year can be guaranteed under physiological conditions (pH = 7.4) when, e.g., artificial muscles for biomimetic robots as potential application for these kind of shape-memory polymer actuators will be addressed. Y1 - 2019 U6 - https://doi.org/10.1557/adv.2019.202 SN - 2059-8521 VL - 4 IS - 21 SP - 1193 EP - 1205 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Balk, Maria A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation JF - MRS advances : a journal of the Materials Research Society (MRS) N2 - Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time. In this work, glycolide units were incorporated in poly(epsilon-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(epsilon-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 +/- 0.5 kg center dot mol(-1)) including a glycolide content of 8, 16, and 26 mol% (ratio 1:1:1 wt%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 degrees C. The hydrolytic degradation of programmed OCG actuators (200% of elongation) resulted in a reduction of sample mass to 51 wt% within 21 days at pH = 7.4 and 40 degrees C. Degradation results in a decrease of T-m associated to the actuating units and increasing T-m associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized. KW - actuation KW - shape memory KW - polymer KW - crystalline Y1 - 2020 U6 - https://doi.org/10.1557/adv.2019.447 SN - 2059-8521 VL - 5 IS - 12-13 SP - 655 EP - 666 PB - Cambridge University Press CY - New York, NY ER - TY - JOUR A1 - Balk, Maria A1 - Behl, Marc A1 - Nöchel, Ulrich A1 - Lendlein, Andreas T1 - Enzymatically triggered Jack-in-the-box-like hydrogels JF - ACS applied materials & interfaces / American Chemical Society N2 - Enzymes can support the synthesis or degradation of biomacromolecules in natural processes. Here, we demonstrate that enzymes can induce a macroscopic-directed movement of microstructured hydrogels following a mechanism that we call a "Jack-in-the-box" effect. The material's design is based on the formation of internal stresses induced by a deformation load on an architectured microscale, which are kinetically frozen by the generation of polyester locking domains, similar to a Jack-in-thebox toy (i.e., a compressed spring stabilized by a closed box lid). To induce the controlled macroscopic movement, the locking domains are equipped with enzyme-specific cleavable bonds (i.e., a box with a lock and key system). As a result of enzymatic reaction, a transformed shape is achieved by the release of internal stresses. There is an increase in entropy in combination with a swelling-supported stretching of polymer chains within the microarchitectured hydrogel (i.e., the encased clown pops-up with a pre-stressed movement when the box is unlocked). This utilization of an enzyme as a physiological stimulus may offer new approaches to create interactive and enzyme-specific materials for different applications such as an optical indicator of the enzyme's presence or actuators and sensors in biotechnology and in fermentation processes. KW - enzyme KW - hydrogels KW - stimuli-sensitive materials KW - shape change KW - poly(e-caprolactone) KW - switch KW - microporous Y1 - 2021 U6 - https://doi.org/10.1021/acsami.1c00466 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 7 SP - 8095 EP - 8101 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Banerjee, Shiladitya A1 - Saalfrank, Peter T1 - Vibrationally resolved absorption, emission and resonance Raman spectra of diamondoids: a study based on time-dependent correlation functions JF - Physical chemistry, chemical physics : a journal of European Chemical Societies Y1 - 2014 U6 - https://doi.org/10.1039/c3cp53535e SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 1 SP - 144 EP - 158 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Banerjee, Shiladitya A1 - Saalfrank, Peter T1 - Vibrationally resolved absorption, emission and resonance Raman spectra of diamondoids : a study based on time- dependent correlation functions Y1 - 2014 UR - http://pubs.rsc.org/en/content/articlehtml/2014/cp/c3cp53535e U6 - https://doi.org/10.1039/C3CP53535E ER - TY - JOUR A1 - Banerjee, Shiladitya A1 - Stueker, Tony A1 - Saalfrank, Peter T1 - Vibrationally resolved optical spectra of modified diamondoids obtained from time-dependent correlation function methods JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Optical properties of modified diamondoids have been studied theoretically using vibrationally resolved electronic absorption, emission and resonance Raman spectra. A time-dependent correlation function approach has been used for electronic two-state models, comprising a ground state (g) and a bright, excited state (e), the latter determined from linear-response, time-dependent density functional theory (TD-DFT). The harmonic and Condon approximations were adopted. In most cases origin shifts, frequency alteration and Duschinsky rotation in excited states were considered. For other cases where no excited state geometry optimization and normal mode analysis were possible or desired, a short-time approximation was used. The optical properties and spectra have been computed for (i) a set of recently synthesized sp(2)/sp(3) hybrid species with CQC double-bond connected saturated diamondoid subunits, (ii) functionalized (mostly by thiol or thione groups) diamondoids and (iii) urotropine and other C-substituted diamondoids. The ultimate goal is to tailor optical and electronic features of diamondoids by electronic blending, functionalization and substitution, based on a molecular-level understanding of the ongoing photophysics. Y1 - 2015 U6 - https://doi.org/10.1039/c5cp02615f SN - 1463-9076 SN - 1463-9084 VL - 17 IS - 29 SP - 19656 EP - 19669 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Banerjee, Shiladitya A1 - Stüker, Tony A1 - Saalfrank, Peter T1 - Vibrationally resolved optical spectra of modified diamondoids obtained from time-dependent correlation function methods JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - Optical properties of modified diamondoids have been studied theoretically using vibrationally resolved electronic absorption, emission and resonance Raman spectra. A time-dependent correlation function approach has been used for electronic two-state models, comprising a ground state (g) and a bright, excited state (e), the latter determined from linear-response, time-dependent density functional theory (TD-DFT). The harmonic and Condon approximations were adopted. In most cases origin shifts, frequency alteration and Duschinsky rotation in excited states were considered. For other cases where no excited state geometry optimization and normal mode analysis were possible or desired, a short-time approximation was used. The optical properties and spectra have been computed for (i) a set of recently synthesized sp2/sp3 hybrid species with C[double bond, length as m-dash]C double-bond connected saturated diamondoid subunits, (ii) functionalized (mostly by thiol or thione groups) diamondoids and (iii) urotropine and other C-substituted diamondoids. The ultimate goal is to tailor optical and electronic features of diamondoids by electronic blending, functionalization and substitution, based on a molecular-level understanding of the ongoing photophysics. Y1 - 2015 U6 - https://doi.org/10.1039/C5CP02615F SN - 1463-9084 SN - 1463-9076 VL - 17 IS - 29 SP - 19656 EP - 19669 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Banße, Wolfgang A1 - Fliegner, Jana Ute A1 - Hennig, H. A1 - Lehmann, Andreas A1 - Uhlemann, Erhard A1 - Tschwatschal, F. T1 - Ligand exchange reactions of molybdenum hexacarbonyl with tridentate diacidic ligands Y1 - 1997 ER - TY - JOUR A1 - Bapolisi, Alain Murhimalika A1 - Kielb, Patrycja A1 - Bekir, Marek A1 - Lehnen, Anne-Catherine A1 - Radon, Christin A1 - Laroque, Sophie A1 - Wendler, Petra A1 - Müller-Werkmeister, Henrike A1 - Hartlieb, Matthias T1 - Antimicrobial polymers of linear and bottlebrush architecture BT - Probing the membrane interaction and physicochemical properties JF - Macromolecular rapid communications : publishing the newsletters of the European Polymer Federation N2 - Polymeric antimicrobial peptide mimics are a promising alternative for the future management of the daunting problems associated with antimicrobial resistance. However, the development of successful antimicrobial polymers (APs) requires careful control of factors such as amphiphilic balance, molecular weight, dispersity, sequence, and architecture. While most of the earlier developed APs focus on random linear copolymers, the development of APs with advanced architectures proves to be more potent. It is recently developed multivalent bottlebrush APs with improved antibacterial and hemocompatibility profiles, outperforming their linear counterparts. Understanding the rationale behind the outstanding biological activity of these newly developed antimicrobials is vital to further improving their performance. This work investigates the physicochemical properties governing the differences in activity between linear and bottlebrush architectures using various spectroscopic and microscopic techniques. Linear copolymers are more solvated, thermo-responsive, and possess facial amphiphilicity resulting in random aggregations when interacting with liposomes mimicking Escheria coli membranes. The bottlebrush copolymers adopt a more stable secondary conformation in aqueous solution in comparison to linear copolymers, conferring rapid and more specific binding mechanism to membranes. The advantageous physicochemical properties of the bottlebrush topology seem to be a determinant factor in the activity of these promising APs. KW - antimicrobial polymers KW - bottlebrush copolymers KW - liposomes KW - membrane KW - interactions KW - quartz crystal microbalance Y1 - 2022 U6 - https://doi.org/10.1002/marc.202200288 SN - 1521-3927 SN - 1022-1336 VL - 43 IS - 19 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Keinpeter, Erich T1 - Quantification of the aromaticity of 2-Alkylidenethiazolines subjected to push-pull activity JF - The journal of organic chemistry N2 - Through-space NMR shieldings (TSNMRSs) of a series of 2-alkylidenethiazolines subjected to push-pull activity have been calculated by the GIAO method employing the nucleus-independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSSs). The ICSSs were applied to quantify and visualize the degree of aromaticity of the studied compounds, which has been shown to be in excellent correlation with the push-pull behavior, quantified by the quotient (pi*/pi) method. Dissection of the absolute magnetic shielding values into individual contributions of bonds and lone pairs by the natural chemical shielding-natural bond orbital (NCS-NBO) analysis has revealed unexpected details. Y1 - 2011 U6 - https://doi.org/10.1021/jo200294f SN - 0022-3263 VL - 76 IS - 10 SP - 3861 EP - 3871 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Klaumuenzer, Ute A1 - Markovic, Rade A1 - Kleinpeter, Erich T1 - Structure, configuration, conformation and quantification of the push pull-effect of 2-alkylidene-4- thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives N2 - Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, C-13 NMR chemical shifts of the C-2, C-2', C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient pi*/pi, length of the partial double bond, C-13 NMR chemical shift difference (Delta delta(C=C)) and H-1 NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push- pull C=C double bond is discussed, too. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2010.09.040 SN - 0040-4020 ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity. KW - anisotropic effects KW - aromaticity KW - B,N heterocycles KW - density functional calculations KW - NMR spectroscopy Y1 - 2012 U6 - https://doi.org/10.1002/cphc.201200732 SN - 1439-4235 VL - 13 IS - 17 SP - 3803 EP - 3811 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct? JF - Chemistry - a European journal N2 - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring. KW - ab initio calculations KW - anisotropic effects KW - NMR spectroscopy KW - nucleus-independent chemical shift KW - pi interactions Y1 - 2012 U6 - https://doi.org/10.1002/chem.201101882 SN - 0947-6539 VL - 18 IS - 1 SP - 370 EP - 376 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Tatar, Jovanan A1 - Kleinpeter, Erich A1 - Markovic, Rade T1 - High-Yield Synthesis of Substituted and Unsubstituted Pyridinium Salts Containing a 4-Oxothiazolidine Moiety N2 - A new series of unsubstituted and substituted pyridinium salts bearing a 4-oxothiazolidinyl moiety has been prepared by an efficient rearrangement of 2-(1-bromoalkylidene)thiazolidin-4-ones. The process in based on three steps, namely carbon-bromine cleavage, bromine transfer, and substitution, each induced by pyridine or its derivatives, acting as base and reactant. Y1 - 2008 ER - TY - JOUR A1 - Baraza, Lilechi D. A1 - Neser, Wekesa A1 - Jackson, Korir Cheruiyot A1 - Fredrick, Juma B. A1 - Dennis, Ochieno A1 - Wairimu, Kamau R. A1 - Keya, Aggrey Osogo A1 - Heydenreich, Matthias T1 - Antimicrobial Coumarins from the Oyster Culinary-Medicinal Mushroom, Pleurotus ostreatus (Agaricomycetes), from Kenya JF - International journal of medicinal mushrooms N2 - Pleurotus ostreatus has been widely used as food because of its nutritional and medicinal properties. These have been attributed to the presence of macronutrients, minerals, vitamins, and amino acids, among other secondary metabolites. There are, however, few reports on the antimicrobial activities of different classes of purified compounds from P. ostreatus. This led to the current study, the objective of which was to chemically characterize the antibiotic activities of P. ()streams against selected human pathogenic bacteria and endophytic fungi. Chemical structures were determined using spectroscopic methods and by comparison with values of related structures reported in the literature. Pure compounds from P. ostreatus were tested in vitro against pathogenic bacteria (Staphylococcus aureus and Escherichia coli) and endophytic fungi (Pencillium digitatum and Fusarium prolferatum). A new compound, (E)-5,7-dimethoxy-6-(3-methylbuta-1,3-dienyl)-2H-chromen-2-one (5-methoxy-(E)-suberodiene) (compound 2), along with ergosterol (compound I.) and 5,7-dimethoxy-6-(3-methylbut-2-enyl)-2H-chromen-2-one (toddaculin; compound 3), were isolated from the fruiting bodies of P. ostreatus. The growth of S. aureus,E proliferatum, and P. digitatum colonies was inhibited in media containing compound 2, with minimum inhibitory concentrations closely comparable to those of conventional antibiotics. KW - Escherichia coli KW - Fusarium proliferatum KW - medicinal mushrooms KW - Penicillium digitatum KW - Pleurotus ostreatus KW - Staphylococcus aureus Y1 - 2016 U6 - https://doi.org/10.1615/IntJMedMushrooms.v18.i10.60 SN - 1521-9437 SN - 1940-4344 VL - 18 SP - 905 EP - 913 PB - Begell House CY - Danbury ER - TY - JOUR A1 - Barta, Petra A1 - Szatmari, Istvan A1 - Fueloep, Ferenc A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Synthesis and stereochemistry of new naphth[1,3]oxazino[3,2-a] benzazepine and naphth[1,3]oxazino[3,2-e]thienopyridine derivatives JF - Tetrahedron N2 - Through the reactions of 1- or 2-naphthol and 4,5-dihydro-3H-benz[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine, new aminonaphthol derivatives were prepared. The syntheses were extended by using N-containing naphthol analogues such as 5-hydroxyisoquinoline and 6-hydroxyquinoline. The ring closures of the novel bifunctional compounds were also achieved, resulting in new naphth[2,1-e][1,3]oxazines, naphth[1,2-e][1,3]oxazines, isoquinolino[5,6-e][1,3]oxazines and quinolino[5,6-e][1,3]oxazines. H-1 NMR spectra of the target heterocycles 16, 20 and 21 were sufficiently resolved to indentify the present stereochemistry; therefore, beside computed structures, spatial experimental (dipolar coupling-NOE) and computed (ring current effect of the naphthyl moiety-TSNMRS) NMR studies were employed. The studied heterocycles exist exclusively as S(14b),R(N), R(14b),S(N), and S(16b)S(N) isomers, respectively. The flexible moieties of the studied compounds prefer. (C) 2016 Elsevier Ltd. All rights reserved. KW - Modified Mannich reaction KW - Thienopyridine KW - Benzazepine KW - NMR spectroscopy KW - Stereochemistry KW - Theoretical calculations Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2016.03.058 SN - 0040-4020 VL - 72 SP - 2402 EP - 2410 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Barth, Johannes A1 - Siegmann, Rebekka A1 - Beuermann, Sabine A1 - Russell, Gregory T. A1 - Buback, Michael T1 - Investigations into chain-length-dependent termination in bulk radical polymerization of 1H, 1H, 2H, 2H-Tridecafluorooctyl methacrylate JF - Macromolecular chemistry and physics N2 - The SP-PLP-EPR technique is used to carry out a detailed investigation of the radical termination kinetics of 1H, 1H, 2H, 2H-tridecafluorooctyl methacrylate (TDFOMA) in bulk at relatively low conversion. Composite-model behavior for chain-length-dependent termination rate coefficients, kti,i, is observed. It is found that for TDFOMA, ic approximate to 60 independent of temperature, and as approximate to 0.65 and al approximate to 0.2 at 80 degrees C and above. However, at lower temperatures the situation is strikingly different, with the significantly higher average values of as = 0.89 +/- 0.15 and al = 0.32 +/- 0.10 being obtained at 50 degrees C and below. This makes TDFOMA the first monomer to be found that exhibits clearly different exponent values, as and al, at lower and higher temperature, and that has both a high as, like an acrylate, and a high ic, like a methacrylate. KW - ESR KW - EPR KW - kinetics (polym KW - ) KW - methacrylates KW - radical polymerization KW - termination Y1 - 2012 U6 - https://doi.org/10.1002/macp.201100479 SN - 1022-1352 VL - 213 IS - 1 SP - 19 EP - 28 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Bartlett, Nate C. -M. A1 - Jankunas, Justin A1 - Goswami, Tapas A1 - Zare, Richard N. A1 - Bouakline, Foudhil A1 - Althorpe, Stuart C. T1 - Differential cross sections for H + D-2 -> HD(v '=2, j '=0,3,6,9) + D at center-of-mass collision energies of 1.25, 1.61, and 1.97 eV JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - We have measured differential cross sections (DCSs) for the reaction H + D-2 -> HD- (v' = 2, j' = 0,3,6,9) + D at center-of-mass collision energies E-coll of 1.25, 1.61, and 1.97 eV using the photoloc technique. The DCSs show a strong dependence on the product rotational quantum number. For the HD(v' = 2, j' = 0) product, the DCS is bimodal but becomes oscillatory as the collision energy is increased. For the other product states, they are dominated by a single peak, which shifts from back to sideward scattering as j' increases, and they are in general less sensitive to changes in the collision energy. The experimental results are compared to quantum mechanical calculations and show good, but not fully quantitative agreement. Y1 - 2011 U6 - https://doi.org/10.1039/c0cp02460k SN - 1463-9076 VL - 13 IS - 18 SP - 8175 EP - 8179 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bartoloni, Marco A1 - Jin, Xian A1 - Marcaida, Maria José A1 - Banha, Joao A1 - Dibonaventura, Ivan A1 - Bongoni, Swathi A1 - Bartho, Kathrin A1 - Gräbner, Olivia A1 - Sefkow, Michael A1 - Darbre, Tamis A1 - Reymond, Jean-Louis T1 - Bridged bicyclic peptides as potential drug scaffolds BT - synthesis, structure, protein binding and stability JF - Chemical Science N2 - Double cyclization of short linear peptides obtained by solid phase peptide synthesis was used to prepare bridged bicyclic peptides (BBPs) corresponding to the topology of bridged bicyclic alkanes such as norbornane. Diastereomeric norbornapeptides were investigated by 1H-NMR, X-ray crystallography and CD spectroscopy and found to represent rigid globular scaffolds stabilized by intramolecular backbone hydrogen bonds with scaffold geometries determined by the chirality of amino acid residues and sharing structural features of β-turns and α-helices. Proteome profiling by capture compound mass spectrometry (CCMS) led to the discovery of the norbornapeptide 27c binding selectively to calmodulin as an example of a BBP protein binder. This and other BBPs showed high stability towards proteolytic degradation in serum. Y1 - 2015 U6 - https://doi.org/10.1039/C5SC01699A SN - 2041-6520 SN - 2041-6539 VL - 10 IS - 6 SP - 5473 EP - 5490 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bastian, Philipp U. A1 - Nacak, Selma A1 - Roddatis, Vladimir A1 - Kumke, Michael Uwe T1 - Tracking the motion of lanthanide ions within core-shell-shell NaYF4 nanocrystals via resonance energy transfer JF - The journal of physical chemistry : C N2 - Lanthanide resonance energy transfer (LRET) was used to investigate the motion of dopant ions during the synthesis of core-shell-shell-nanocrystals (NCs) that are frequently used as frequency upconversion materials. Reaction conditions (temperature, solvent) as well as lattice composition and precursors were adapted from a typical hydrothermal synthesis approach used to obtain upconversion nanoparticles (UCNPs). Instead of adding the lanthanide ions Yb3+/Er3+ as the sensitizer/activator couple, Eu3+/Nd3+ as the donor/acceptor were added as the LRET pair to the outer shell (Eu-3) and the core (Nd-3). By tailoring the thickness of the insulation shell ("middle shell"), the expected distance between the donor and the acceptor was increased beyond 2 R-0, a distance for which no LRET is expected. The successful synthesis of core- shell-shell NCs with different thicknesses of the insulation layer was demonstrated by high-resolution transmission electron microscopy measurement. The incorporation of the Eu3+ ions into the NaYF4 lattice was investigated by high-resolution time-resolved luminescence measurements. Two major Eu3+ species (bulk and surface) were found. This was supported by steady-state as well as time-resolved luminescence data. Based on the luminescence decay kinetics, the intermixing of lanthanides during synthesis of core- shell UCNPs was evaluated. The energy transfer between Eu3+ (donor) and Nd3+ (acceptor) ions was exploited to quantify the motion of the dopant ions. This investigation reveals the migration of Ln(3+) ions between different compatiments in core-shell NCs and affects the concept of using core-shell architectures to increase the efficiency of UCNPs. In order to obtain well-separated core and shell structures with different dopants, alternative concepts are needed. Y1 - 2020 U6 - https://doi.org/10.1021/acs.jpcc.0c02588 SN - 1932-7447 SN - 1932-7455 VL - 124 IS - 20 SP - 11229 EP - 11238 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Bastian, Philipp U. A1 - Robel, Nathalie A1 - Schmidt, Peter A1 - Schrumpf, Tim A1 - Günter, Christina A1 - Roddatis, Vladimir A1 - Kumke, Michael U. T1 - Resonance energy transfer to track the motion of lanthanide ions BT - what drives the intermixing in core-shell upconverting nanoparticles? JF - Biosensors : open access journal N2 - The imagination of clearly separated core-shell structures is already outdated by the fact, that the nanoparticle core-shell structures remain in terms of efficiency behind their respective bulk material due to intermixing between core and shell dopant ions. In order to optimize the photoluminescence of core-shell UCNP the intermixing should be as small as possible and therefore, key parameters of this process need to be identified. In the present work the Ln(III) ion migration in the host lattices NaYF4 and NaGdF4 was monitored. These investigations have been performed by laser spectroscopy with help of lanthanide resonance energy transfer (LRET) between Eu(III) as donor and Pr(III) or Nd(III) as acceptor. The LRET is evaluated based on the Forster theory. The findings corroborate the literature and point out the migration of ions in the host lattices. Based on the introduced LRET model, the acceptor concentration in the surrounding of one donor depends clearly on the design of the applied core-shell-shell nanoparticles. In general, thinner intermediate insulating shells lead to higher acceptor concentration, stronger quenching of the Eu(III) donor and subsequently stronger sensitization of the Pr(III) or the Nd(III) acceptors. The choice of the host lattice as well as of the synthesis temperature are parameters to be considered for the intermixing process. KW - upconversion nanoparticles KW - lanthanoid migration KW - lanthanides KW - core-shell KW - energy transfer Y1 - 2021 U6 - https://doi.org/10.3390/bios11120515 SN - 2079-6374 VL - 11 IS - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bastian, Philipp U. A1 - Yu, Leixiao A1 - de Guereñu Kurganova, Anna Lopez A1 - Haag, Rainer A1 - Kumke, Michael Uwe T1 - Bioinspired confinement of upconversion nanoparticles for improved performance in aqueous solution JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The resonance energy transfer (RET) from NaYF4:Yb,Er upconverting nanoparticles (UNCPs) to a dye (5-carboxytetramethylrhodamine (TAMRA)) was investigated by photoluminescence experiments and microscale thermophoresis (MST). The dye was excited via RET from the UCNPs which was excited in the near-infrared (NIR). The change of the dye diffusion speed (free vs coupled) was investigated by MST. RET shows significant changes in the decay times of the dye as well as of the UCNPs. MST reveals significant changes in the diffusion speed. A unique amphiphilic coating polymer (customized mussel protein (CMP) polymer) for UCNP surface coating was used, which mimics blood protein adsorption and mussel food protein adhesion to transfer the UCNP into the aqueous phase and to allow surface functionalization. The CMP provides very good water dispersibility to the UCNPs and minimizes ligand exchange and subsequent UCNP aging reactions because of the interlinkage of the CMP on the UCNP surface. Moreover, CMP provides N-3-functional groups for dick chemistry-based functionalization demonstrated with the dye 5-carboxytetramethylrhodamine (TAMRA). This establishes the principle coupling scheme for suitable biomarkers such as antibodies. The CMP provides very stable aqueous UCNP dispersions that are storable up to 3 years in a fridge at 5 degrees C without dissolution or coagulation. The outstanding properties of CMP in shielding the UCNP from unwanted solvent effects is reflected in the distinct increase of the photoluminescence decay times after UCNP functionalization. The UCNP-to-TAMRA energy transfer is also spectroscopically investigated at low temperatures (4-200 K), revealing that one of the two green Er(III) emission bands contributes the major part to the energy transfer. The TAMRA fluorescence decay time increases by a factor of 9500 from 2.28 ns up to 22 mu s due to radiationless energy transfer from the UCNP after NIR excitation of the latter. This underlines the unique properties of CMP as a versatile capping ligand for distinctly improving the UCNPs' performance in aqueous solutions, for coupling of biomolecules, and for applications for in vitro and in vivo experiments using UCNPs as optical probes in life science applications. Y1 - 2020 U6 - https://doi.org/10.1021/acs.jpcc.0c09798 SN - 1932-7447 SN - 1932-7455 VL - 124 IS - 52 SP - 28623 EP - 28635 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Bauch, Marcel A1 - Böttcher, Dominique A1 - Bornscheuer, Uwe T. A1 - Linker, Torsten T1 - Enzymatic Cleavage of Aryl Acetates JF - ChemCatChem : heterogeneous & homogeneous & bio- & nano-catalysis ; a journal of ChemPubSoc Europe N2 - Seven enzymes have been screened for the cleavage of aryl acetates. Phenyl and naphthyl acetates react with lipases and esterases, whereas the sterically demanding anthracene acetate gave a conversion only with porcine liver esterase and esterase 2 from Bacillus subtilis (BS2). These two enzymes have been employed on a preparative (0.5 mmol) scale and afforded cleavage products in 91 and 94% yields, even for anthracene acetate. Thus, this method is superior to chemical cleavage with catalytic amounts of sodium methoxide (Zemplen conditions), which gave only low conversions. Finally, regioselectivity has been achieved with an anthracene bisacetate, in which an ethyl group controls the cleavage of the first acetate. This indicates that steric interactions play a crucial role in the enzymatic cleavage of aryl acetates, which might be interesting for future applications or the development of enzyme inhibitors. KW - arenes KW - enzyme catalysis KW - regioselectivity KW - steric hindrance KW - substituent effects Y1 - 2016 U6 - https://doi.org/10.1002/cctc.201600678 SN - 1867-3880 SN - 1867-3899 VL - 8 SP - 2853 EP - 2857 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bauch, Marcel A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Stereoselective [4+2] Cycloaddition of Singlet Oxygen to Naphthalenes Controlled by Carbohydrates JF - Molecules : a journal of synthetic chemistry and natural product chemistry N2 - Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form. KW - singlet oxygen KW - photooxygenation KW - naphthalenes KW - carbohydrates KW - stereoselectivity KW - auxiliary control KW - [4+2] cycloaddition Y1 - 2021 U6 - https://doi.org/10.3390/molecules26040804 SN - 1420-3049 VL - 16 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bauch, Marcel A1 - Klaper, Matthias A1 - Linker, Torsten T1 - Intermediates in the cleavage of endoperoxides JF - Journal of physical organic chemistry N2 - The decomposition of anthracene endoperoxides has been investigated under various conditions. Thermolyses proceed via radical intermediates and afford anthracenes and rearrangement products, depending on the substitution pattern. Interestingly, not only the O-O but also the C-O bond can be cleaved homolytically. Under basic conditions fragmentations take place, affording anthraquinone, and reactive oxygen species. This mechanism explains the often observed decomposition of endoperoxides during work-up. Finally, an acid-catalyzed cleavage has been observed under release of hydrogen peroxide. The results should be interesting for the mechanistic understanding of peroxide decomposition and the endoperoxides might serve as mild sources of reactive oxygen species for future applications. Copyright (C) 2016 John Wiley & Sons, Ltd. KW - peroxides KW - radicals KW - reaction mechanism KW - reactive intermediates Y1 - 2017 U6 - https://doi.org/10.1002/poc.3607 SN - 0894-3230 SN - 1099-1395 VL - 30 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Bauch, Marcel A1 - Krtitschka, Angela A1 - Linker, Torsten T1 - Photooxygenation of oxygen-substituted naphthalenes JF - Journal of physical organic chemistry N2 - The reaction of oxygen-substituted naphthalenes with singlet oxygen (O-1(2)) has been investigated, and labile endoperoxides have been isolated and characterized at -78 degrees C for the first time. Low-temperature kinetics by UV spectroscopy revealed that alkoxy and silyloxy substituents remarkably increase the rate of photooxygenations compared to 1,4-dimethylnaphthalene, whereas acyloxy-substituted acenes are inert towards O-1(2). The reactivities nicely correlate with HOMO energies and free activation energies, which we determined by density functional theory calculations. The lability of the isolated endoperoxides is due to their very fast back reaction to the corresponding naphthalenes even at -20 degrees C under release of O-1(2), making them to superior sources of this reactive species under very mild conditions. Finally, a carbohydrate-substituted naphthalene has been synthesized, which reacts reversibly with O-1(2) and might be applied for enantioselective oxidations in future work. KW - kinetics KW - labile peroxides KW - low-temperature experiments KW - naphthalenes KW - singlet oxygen Y1 - 2017 U6 - https://doi.org/10.1002/poc.3734 SN - 0894-3230 SN - 1099-1395 VL - 30 SP - 6803 EP - 6813 PB - Wiley CY - Hoboken ER -