TY  - JOUR
A1  - Brosnan, Sarah M.
A1  - Schlaad, Helmut
T1  - Modification of polypeptide materials by Thiol-X chemistry
JF  - Polymer : the international journal for the science and technology of polymers
N2  - Thiol-X chemistry has proven to be a valuable toolbox for modification of peptides, proteins, monomers, and polymers. Recently, this has become especially true for the modification of polypeptides (monomers or polymers), which has resulted in a plethora of novel polymers and materials. With this in mind, this highlight focuses on the recent literature concerning the modification of polypeptides by the use of thiol-X chemistry, in particular to synthetic polypeptides either at the monomer or polymer stage modified by thiol-ene, -Michael addition, and -yne chemistries. (C) 2014 Published by Elsevier Ltd.
KW  - Polypeptide
KW  - Thiol-X
KW  - Click chemistry
Y1  - 2014
U6  - https://doi.org/10.1016/j.polymer.2014.08.067
SN  - 0032-3861
SN  - 1873-2291
VL  - 55
IS  - 22
SP  - 5511
EP  - 5516
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Friess, Fabian
A1  - Lendlein, Andreas
A1  - Wischke, Christian
T1  - Photoinduced synthesis of polyester networks from methacrylate functionalized precursors: analysis of side reactions
JF  - Polymers for advanced technologies
N2  - Polyester networks can be prepared by ultraviolet (UV)-light-induced radical polymerization of methacrylate functionalized oligo(epsilon-caprolactone)s. The properties and functions of the obtained materials depend on defined network structures and may be altered, if crosslinking would occur by side reactions in other positions than the methacrylate endgroups. In order to explore whether and to which extent such side reactions occur, network synthesis as well as related model reactions were performed in the absence of photoinitiator. Hereby precursor structures (linear and four-arm star-shaped) and reaction conditions (in solution and in the melt) were varied. Unspecific side reactions were found only upon extensive UV irradiation for 60min (26 mW cm(-2)) with minor but detectable alterations of physicochemical properties of the networks. The analysis of model reactions suggested minor photolytic cleavage of ester bonds during polymer network synthesis. However, the effect of these side reactions on network properties and functions appeared to be less relevant than an incomplete precursor integration because of a too short UV irradiation for crosslinking. Copyright (c) 2014 John Wiley & Sons, Ltd.
KW  - poly(epsilon-caprolactone) methacrylate
KW  - crosslinking
KW  - excimer UV light
KW  - side reaction
KW  - photoinduced radical polymerization
Y1  - 2014
U6  - https://doi.org/10.1002/pat.3313
SN  - 1042-7147
SN  - 1099-1581
VL  - 25
IS  - 11
SP  - 1285
EP  - 1292
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Boggio, Jose M. Chavez
A1  - Bodenmueller, D.
A1  - Fremberg, T.
A1  - Haynes, R.
A1  - Roth, Martin M.
A1  - Eisermann, R.
A1  - Lisker, M.
A1  - Zimmermann, L.
A1  - Boehm, Michael
T1  - Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization
JF  - Journal of the Optical Society of America : B, Optical physics
N2  - Dispersion engineering in silicon nitride (SiXNY) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multicladding arrangement. Ultraflat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during fabrication of the SiXNY waveguides are a limitation for obtaining ultraflat dispersion profiles. Single- and multicladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in single-and multicladding waveguides with small refractive index contrast (3%). A flat dispersion profile with +/- 3.2 ps/nm/km variation over 500 nm is obtained in a multicladding waveguide fabricated with a refractive index contrast of 37%. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multicladding SiXNY waveguide. (C) 2014 Optical Society of America
Y1  - 2014
U6  - https://doi.org/10.1364/JOSAB.31.002846
SN  - 0740-3224
SN  - 1520-8540
VL  - 31
IS  - 11
SP  - 2846
EP  - 2857
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mai, Tobias
A1  - Rakhmatullina, Ekaterina
A1  - Bleek, Katrin
A1  - Boye, Susanne
A1  - Yuan, Jiayin
A1  - Voelkel, Antje
A1  - Graewert, Marlies
A1  - Cheaib, Zeinab
A1  - Eick, Sigrun
A1  - Günter, Christina
A1  - Lederer, Albena
A1  - Lussi, Adrian
A1  - Taubert, Andreas
T1  - Poly(ethylene oxide)-b-poly(3-sulfopropyl methacrylate) block copolymers for calcium phosphate mineralization and biofilm inhibition
JF  - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences
N2  - Poly(ethylene oxide) (PEO) has long been used as an additive in toothpaste, partly because it reduces biofilm formation on teeth. It does not, however, reduce the formation of dental calculus or support the remineralization of dental enamel or dentine. The present article describes the synthesis of new block copolymers on the basis of PEO and poly(3-sulfopropyl methacrylate) blocks using atom transfer radical polymerization. The polymers have very large molecular weights (over 10(6) g/mol) and are highly water-soluble. They delay the precipitation of calcium phosphate from aqueous solution but, upon precipitation, lead to relatively monodisperse hydroxyapatite (HAP) spheres. Moreover, the polymers inhibit the bacterial colonization of human enamel by Streptococcus gordonii, a pioneer bacterium in oral biofilm formation, in vitro. The formation of well-defined HAP spheres suggests that a polymer-induced liquid precursor phase could be involved in the precipitation process. Moreover, the inhibition of bacterial adhesion suggests that the polymers could be utilized in caries prevention.
Y1  - 2014
U6  - https://doi.org/10.1021/bm500888q
SN  - 1525-7797
SN  - 1526-4602
VL  - 15
IS  - 11
SP  - 3901
EP  - 3914
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Pereira, Fernanda S.
A1  - Nascimento, Heliara D. L.
A1  - Magalhaes, Alvicler
A1  - Peter, Martin G.
A1  - Bataglion, Giovana Anceski
A1  - Eberlin, Marcos N.
A1  - Gonzalez, Eduardo R. P.
T1  - ESI(+)-MS and GC-MS study of the hydrolysis of N-azobenzyl derivatives of chitosan
JF  - Molecules
N2  - New N-p-chloro-, N-p-bromo-, and N-p-nitrophenylazobenzylchitosan derivatives, as well as the corresponding azophenyl and azophenyl-p-sulfonic acids, were synthesized by coupling N-benzylvchitosan with aryl diazonium salts. The synthesized molecules were analyzed by UV-Vis, FT-IR, H-1-NMR and N-15-NMR spectroscopy. The capacity of copper chelation by these materials was studied by AAS. Chitosan and the derivatives were subjected to hydrolysis and the products were analyzed by ESI(+)-MS and GC-MS, confirming the formation of N-benzyl chitosan. Furthermore, the MS results indicate that a nucleophilic aromatic substitution (SnAr) reaction occurs under hydrolysis conditions, yielding chloroaniline from N-p-bromo-, and N-p-nitrophenylazo-benzylchitosan as well as bromoaniline from N-p-chloro-, and N-p-nitrophenylazobenzyl-chitosan.
KW  - chitosan
KW  - N-azobenzylchitosan
KW  - ESI-MS
KW  - GC-MS
KW  - SnAr reaction
Y1  - 2014
U6  - https://doi.org/10.3390/molecules191117604
SN  - 1420-3049
VL  - 19
IS  - 11
SP  - 17604
EP  - 17618
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Tentschert, Jutta
A1  - Jungnickel, Harald
A1  - Reichardt, Philipp
A1  - Leube, Peter
A1  - Kretzschmar, Bernd
A1  - Taubert, Andreas
A1  - Luch, A.
T1  - Identification of nano clay in composite polymers
JF  - Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films
N2  - Industrialized food production is in urgent search for alternative packaging materials, which can serve the requirements of a globalized world in terms of longer product shelf lives, reduced freight weight to decrease transport costs, and better barrier functionality to preserve its freshness. Polymer materials containing organically modified nano clay particles as additives are one example for a new generation of packaging materials with specific barrier functionality to actually hit the market. Clay types used for these applications are aluminosilicates, which belong to the mineral group of phyllosilicates. These consist of nano-scaled thin platelets, which are organically modified with quaternary ammonium compounds acting as spacers between the different clay layers, thereby increasing the hydrophobicity of the mineral additive. A variety of different organically modified clays are already available, and the use as additive for food packaging materials is one important application. To ensure valid risk assessments of emerging nano composite polymers used in the food packaging industry, exact analytical characterization of the organically modified clay within the polymer matrix is of paramount importance. Time-of-flight SIMS in combination with multivariate statistical analysis was used to differentiate modified clay reference materials from another. Time-of-flight SIMS spectra of a reference polymer plate, which contained one specific nano clay composite, were acquired. For each modified clay additive, a set of characteristic diagnostic ions could be identified, which then was used to successfully assign unknown clay additives to the corresponding reference material. Thus, the described methodology could be used to define and characterize nano clay within polymer matrices. Copyright (c) 2014 John Wiley & Sons, Ltd.
KW  - ToF-SIMS
KW  - nanoparticles
KW  - nano clay
KW  - polymer
KW  - food contact material
Y1  - 2014
U6  - https://doi.org/10.1002/sia.5546
SN  - 0142-2421
SN  - 1096-9918
VL  - 46
SP  - 334
EP  - 336
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Degtyar, Elena
A1  - Harrington, Matthew J.
A1  - Politi, Yael
A1  - Fratzl, Peter
T1  - The mechanical role of metal ions in biogenic protein-based materials
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - Protein-metal interactions-traditionally regarded for roles in metabolic processes-are now known to enhance the performance of certain biogenic materials, influencing properties such as hardness, toughness, adhesion, and self-healing. Design principles elucidated through thorough study of such materials are yielding vital insights for the design of biomimetic metallopolymers with industrial and biomedical applications. Recent advances in the understanding of the biological structure-function relationships are highlighted here with a specific focus on materials such as arthropod biting parts, mussel byssal threads, and sandcastle worm cement.
KW  - adhesives
KW  - biomaterials
KW  - metal coordination
KW  - sacrificial bonds
KW  - self-healing materials
Y1  - 2014
U6  - https://doi.org/10.1002/anie.201404272
SN  - 1433-7851
SN  - 1521-3773
VL  - 53
IS  - 45
SP  - 12026
EP  - 12044
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Moskalik, Mikhail Yu.
A1  - Astakhova, Vera V.
A1  - Schilde, Uwe
A1  - Sterkhova, Irina V.
A1  - Shainyan, Bagrat A.
T1  - Assembling of 3,6-diazabicyclo[3.1.0]hexane framework in oxidative triflamidation of substituted buta-1,3-dienes
JF  - Tetrahedron
KW  - Trifluoromethanesulfonamide
KW  - Arenesulfonamides
KW  - Cycloaddition
KW  - 1,3-Dienes
KW  - 3,6-Diazabicyclo[3.1.0]hexanes
KW  - X-ray
Y1  - 2014
U6  - https://doi.org/10.1016/j.tet.2014.09.050
SN  - 0040-4020
VL  - 70
IS  - 45
SP  - 8636
EP  - 8641
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Tritschler, Ulrich
A1  - Zlotnikov, Igor
A1  - Keckeis, Philipp
A1  - Schlaad, Helmut
A1  - Cölfen, Helmut
T1  - Optical properties of self-organized gold nanorod-polymer hybrid films
JF  - Langmuir
N2  - High fractions of gold nanorods were locally aligned by means of a polymeric liquid crystalline phase. The gold nanorods constituting >80 wt % of the thin organic-inorganic composite films form a network with side-by-side and end-to-end combinations. Organization into these network structures was induced by shearing gold nanorod-LC polymer dispersions via spin-coating. The LC polymer is a polyoxazoline functionalized with pendent cholesteryl and carboxyl side groups enabling the polymer to bind to the CTAB stabilizer layer of the gold nanorods via electrostatic interactions, thus forming the glue between organic and inorganic components, and to form a chiral nematic lyotropic phase. The self-assembled locally oriented gold nanorod structuring enables control over collective optical properties due to plasmon resonance coupling, reminiscent of enhanced optical properties of natural biomaterials.
Y1  - 2014
U6  - https://doi.org/10.1021/la503507u
SN  - 0743-7463
VL  - 30
IS  - 46
SP  - 13781
EP  - 13790
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Riemer, Martin
A1  - Schilde, Uwe
T1  - Chroman-4-ones via microwave-promoted domino claisen rearrangement-oxa-michael addition: Synthesis of tabchromones A and B
JF  - Synlett : accounts and rapid communications in synthetic organic chemistry
N2  - Allyl phenyl ethers with a pendant enone substituent undergo, upon microwave irradiation, a domino sequence of Claisen rearrangement and 6-endo-trig-cyclization to furnish functionalized chroman-4-ones. The natural products tabchromones A and B were synthesized via this method.
KW  - cyclization
KW  - Michael addition
KW  - rearrangement
KW  - tandem reaction
KW  - Wacker reaction
Y1  - 2014
U6  - https://doi.org/10.1055/s-0034-1379364
SN  - 0936-5214
SN  - 1437-2096
VL  - 25
IS  - 20
SP  - 2943
EP  - 2946
PB  - Thieme
CY  - Stuttgart
ER  - 
TY  - JOUR
A1  - Schöne, Anne-Christin
A1  - Schulz, Burkhard
A1  - Richau, Klaus
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Characterization of Langmuir films prepared from copolyesterurethanes based on oligo(omega-pentadecalactone) and oligo(epsilon-caprolactone)segments
JF  - Macromolecular chemistry and physics
N2  - A series of multiblock copolymers (PDLCL) synthesized from oligo(omega-pentadecalactone) diol (OPDL) and oligo(epsilon-caprolactone) diol (OCL), which are linked by 2,2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI), is investigated by the Langmuir monolayer technique at the air-water interface. Brewster angle microscopy (BAM) and spectroscopic ellipsometry are employed to characterize the polymer film morphologies in situ. PDLCL containing >= 40 wt% OCL segments form homogeneous Langmuir monofilms after spreading. The film elasticity modulus decreases with increasing amounts of OPDL segments in the copolymer. In contrast, the OCL-free polyesterurethane OPDL-TMDI cannot be spread to monomolecular films on the water surface properly, and movable slabs are observed by BAM even at low surface pressures. The results of the in situ morphological characterization clearly show that essential information concerning the reliability of Langmuir monolayer degradation (LMD) experiments cannot be obtained from the evaluation of the pi-A isotherms only. Consequently, in situ morphological characterization turns out to be indispensable for characterization of Langmuir layers before LMD experiments.
KW  - brewster angle microscopy
KW  - ellipsometry
KW  - Langmuir layers
KW  - morphology
KW  - polyesterurethanes
Y1  - 2014
U6  - https://doi.org/10.1002/macp.201400377
SN  - 1022-1352
SN  - 1521-3935
VL  - 215
IS  - 24
SP  - 2437
EP  - 2445
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Muiva-Mutisya, Lois
A1  - Macharia, Bernard
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Akala, Hoseah M.
A1  - Derese, Solomon
A1  - Omosa, Leonidah K.
A1  - Yusuf, Amir O.
A1  - Kamau, Edwin
A1  - Yenesew, Abiy
T1  - 6 alpha-Hydroxy-alpha-toxicarol and (+)-tephrodin with antiplasmodial activities from Tephrosia species
JF  - Phytochemistry letters
N2  - The CH2Cl2/MeOH (1: 1) extract of the roots of Tephrosia villosa showed good antiplasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 3.1 +/- 0.4 and 1.3 +/- 0.3 mu g/mL, respectively. Chromatographic separation of the extract yielded a new rotenoid, 6 alpha-hydroxy-alpha-toxicarol, along with five known rotenoids, (rotenone, deguelin, sumatrol, 12 alpha-hydroxy-alpha-toxicarol and villosinol). Similar treatment of the extract of the stem of Tephrosia purpurea (IC50 = 4.1 +/- 0.4 and 1.9 +/- 0.2 mu g/mL against D6 and W2 strains of P. falciparum, respectively) yielded a new flavone having a unique substituent at C-7/C-8 [trivial name (+)-tephrodin], along with the known flavonoids tachrosin, obovatin methyl ether and derrone. The relative configuration and the most stable conformation in (+)-tephrodin was determined by NMR and theoretical energy calculations. The rotenoids and flavones tested showed good to moderate antiplasmodial activities (IC50 = 9 +/- 23 mu M). Whereas the cytotoxicity of rotenoids is known, the flavones (+)-tephrodin and tachrosin did not show significant cytotoxicity (IC50 > 100 mu M;) against mammalian African monkey kidney (vero) and human larynx carcinoma (HEp2) cell lines. (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
KW  - Tephrosia villosa
KW  - Tephrosia purpurea
KW  - 6 alpha-Hydroxy-alpha-toxicarol
KW  - (+)-Tephrodin
KW  - Plasmodium falciparum
Y1  - 2014
U6  - https://doi.org/10.1016/j.phytol.2014.09.002
SN  - 1874-3900
SN  - 1876-7486
VL  - 10
SP  - 179
EP  - 183
PB  - Elsevier
CY  - Amsterdam
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  - Kleinpeter, Erich
A1  - Koch, Andreas
A1  - Schulz, Stefanie
A1  - Wacker, Philipp
T1  - Interplay of para- and diatropic ring currents [(anti)aromaticity] of macrocyclic rings subject to conformational influences, further annelation and hydrogenation of aromatic ring moieties
JF  - Tetrahedron
N2  - The spatial magnetic properties (Through Space NMR Shieldings-TSNMRS) of a variety of porphyrins, hemiporphyrazines and tetraoxo[8]circulenes have been computed, visualized as Iso-chemical Shielding Surfaces (ICSS) of various size and direction, and were examined subject to the interplay of present (para)-diatropic ring currents [(anti)aromaticity] and influences on the latter property originating from the macrocyclic ring conformation, further annelation and partial to complete hydrogenation of aromatic ring moieties. Caution seems to be indicated when concluding from a single NICS parameter to present (para)diatropic ring currents [(anti)aromaticity]. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Porphyrins
KW  - Hemiporphyrazines
KW  - Tetraoxo[8]circulenes
KW  - (Anti)aromaticity
KW  - Anisotropy effect
KW  - Theoretical calculations
Y1  - 2014
U6  - https://doi.org/10.1016/j.tet.2014.10.018
SN  - 0040-4020
VL  - 70
IS  - 48
SP  - 9230
EP  - 9239
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Knie, Christopher
A1  - Utecht, Manuel Martin
A1  - Zhao, Fangli
A1  - Kulla, Hannes
A1  - Kovalenko, Sergey
A1  - Brouwer, Albert M.
A1  - Saalfrank, Peter
A1  - Hecht, Stefan
A1  - Bleger, David
T1  - ortho-Fluoroazobenzenes: visible light switches with very long-lived Z isomers
JF  - Chemistry - a European journal
N2  - Improving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing sigma-electron-withdrawing F atoms ortho to the N=N unit leads to both an effective separation of the n -> pi* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/Z iso-merizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n -> pi* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and nature of the EWGs have been varied, and the visible light photoconversions, quantum yields of isomerization, and thermal stabilities have been measured and rationalized by DFT calculations.
KW  - azobenzenes
KW  - photochromism
KW  - photoswitches
KW  - substituent effects
KW  - visible light
Y1  - 2014
U6  - https://doi.org/10.1002/chem.201404649
SN  - 0947-6539
SN  - 1521-3765
VL  - 20
IS  - 50
SP  - 16492
EP  - 16501
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Keller, Adrian
A1  - Rackwitz, Jenny
A1  - Cauet, Emilie
A1  - Lievin, Jacques
A1  - Körzdörfer, Thomas
A1  - Rotaru, Alexandru
A1  - Gothelf, Kurt V.
A1  - Besenbacher, Flemming
A1  - Bald, Ilko
T1  - Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays
JF  - Scientific reports
Y1  - 2014
U6  - https://doi.org/10.1038/srep07391
SN  - 2045-2322
VL  - 4
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Victora, Andrea
A1  - Moeller, Heiko M.
A1  - Exner, Thomas E.
T1  - Accurate ab initio prediction of NMR chemical shifts of nucleic acids and nucleic acids/protein complexes
JF  - Nucleic acids research
N2  - NMR chemical shift predictions based on empirical methods are nowadays indispensable tools during resonance assignment and 3D structure calculation of proteins. However, owing to the very limited statistical data basis, such methods are still in their infancy in the field of nucleic acids, especially when non-canonical structures and nucleic acid complexes are considered. Here, we present an ab initio approach for predicting proton chemical shifts of arbitrary nucleic acid structures based on state-of-the-art fragment-based quantum chemical calculations. We tested our prediction method on a diverse set of nucleic acid structures including double-stranded DNA, hairpins, DNA/protein complexes and chemically-modified DNA. Overall, our quantum chemical calculations yield highly/very accurate predictions with mean absolute deviations of 0.3-0.6 ppm and correlation coefficients (r(2)) usually above 0.9. This will allow for identifying misassignments and validating 3D structures. Furthermore, our calculations reveal that chemical shifts of protons involved in hydrogen bonding are predicted significantly less accurately. This is in part caused by insufficient inclusion of solvation effects. However, it also points toward shortcomings of current force fields used for structure determination of nucleic acids. Our quantum chemical calculations could therefore provide input for force field optimization.
Y1  - 2014
U6  - https://doi.org/10.1093/nar/gku1006
SN  - 0305-1048
SN  - 1362-4962
VL  - 42
IS  - 22
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Saalfrank, Peter
A1  - Juaristi, J. I.
A1  - Alducin, Maite
A1  - Blanco-Rey, Maria
A1  - Muino, R. Diez
T1  - Vibrational lifetimes of hydrogen on lead films : an ab initio molecular dynamics with electronic friction (AIMDEF) study
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - Using density functional theory and Ab Initio Molecular Dynamics with Electronic Friction (AIMDEF), we study the adsorption and dissipative vibrational dynamics of hydrogen atoms chemisorbed on free-standing lead films of increasing thickness. Lead films are known for their oscillatory behaviour of certain properties with increasing thickness, e.g., energy and electron spill-out change in discontinuous manner, due to quantum size effects [G. Materzanini, P. Saalfrank, and P.J.D. Lindan, Phys. Rev. B 63, 235405 (2001)]. Here, we demonstrate that oscillatory features arise also for hydrogen when chemisorbed on lead films. Besides stationary properties of the adsorbate, we concentrate on finite vibrational lifetimes of H-surface vibrations. As shown by AIMDEF, the damping via vibration-electron hole pair coupling dominates clearly over the vibration-phonon channel, in particular for high-frequency modes. Vibrational relaxation times are a characteristic function of layer thickness due to the oscillating behaviour of the embedding surface electronic density. Implications derived from AIMDEF for frictional many-atom dynamics, and physisorbed species will also be given. (C) 2014 AIP Publishing LLC.
Y1  - 2014
U6  - https://doi.org/10.1063/1.4903309
SN  - 0021-9606
SN  - 1089-7690
VL  - 141
IS  - 23
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Goebel, Ronald
A1  - Hesemann, Peter
A1  - Friedrich, Alwin
A1  - Rothe, Regina
A1  - Schlaad, Helmut
A1  - Taubert, Andreas
T1  - Modular thiol-ene chemistry approach towards mesoporous silica monoliths with organically modified pore walls
JF  - Chemistry - a European journal
N2  - The surface modification of mesoporous silica monoliths through thiol-ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol-gel hydrolysis-poly-condensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3-mercaptopropyl) trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore-wall chemistries. Nitrogen sorption, small-angle X-ray scattering, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore-wall functionalization. This report demonstrates that thiol-ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces.
KW  - mesoporous materials
KW  - photochemistry
KW  - sol-gel processes
KW  - surface chemistry
Y1  - 2014
U6  - https://doi.org/10.1002/chem.201403982
SN  - 0947-6539
SN  - 1521-3765
VL  - 20
IS  - 52
SP  - 17579
EP  - 17589
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Cisek, Richard
A1  - Tokarz, Danielle
A1  - Krouglov, Serguei
A1  - Steup, Martin
A1  - Emes, Michael J.
A1  - Tetlow, Ian J.
A1  - Barzda, Virginijus
T1  - Second harmonic generation mediated by aligned water in starch granules
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network.
Y1  - 2014
U6  - https://doi.org/10.1021/jp508751s
SN  - 1520-6106
VL  - 118
IS  - 51
SP  - 14785
EP  - 14794
PB  - American Chemical Society
CY  - Washington
ER  -