@article{SchmidtKorbAbell2017, author = {Schmidt, Marco F. and Korb, Oliver and Abell, Chris}, title = {Antagonists of the miRNA-Argonaute 2 Protein Complex}, series = {Drug Target miRNA: Methods and Protocols}, volume = {1517}, journal = {Drug Target miRNA: Methods and Protocols}, publisher = {Springer}, address = {New York}, isbn = {978-1-4939-6563-2}, issn = {1064-3745}, doi = {10.1007/978-1-4939-6563-2_17}, pages = {239 -- 249}, year = {2017}, abstract = {microRNAs (miRNAs) have been identified as high-value drug targets. A widely applied strategy in miRNA inhibition is the use of antisense agents. However, it has been shown that oligonucleotides are poorly cell permeable because of their complex chemical structure and due to their negatively charged backbone. Consequently, the general application of oligonucleotides in therapy is limited. Since miRNAs' functions are executed exclusively by the Argonaute 2 protein, we therefore describe a protocol for the design of a novel miRNA inhibitor class: antagonists of the miRNA-Argonaute 2 protein complex, so-called anti-miR-AGOs, that not only block the crucial binding site of the target miRNA but also bind to the protein's active site. Due to their lower molecular weight and, thus, more drug-like chemical structure, the novel inhibitor class may show better pharmacokinetic properties than reported oligonucleotide inhibitors, enabling them for potential therapeutic use.}, language = {en} } @article{BalderasValadezAntunezOliveMendezetal.2017, author = {Balderas-Valadez, Ruth Fabiola and Antunez, E. E. and Olive-Mendez, Sion Federico and Pacholski, Claudia and Campos-Alvarez, Jose and Bokhimi, Xim and Agarwal, V.}, title = {Porous silicon pillar and bilayer structure as a nucleation center for the formation of aligned vanadium pentoxide nanorods}, series = {Ceramics International}, volume = {43}, journal = {Ceramics International}, publisher = {Elsevier}, address = {Oxford}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2017.03.114}, pages = {8023 -- 8030}, year = {2017}, abstract = {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.}, language = {en} } @article{AtilawDuffyHeydenreichetal.2017, author = {Atilaw, Yoseph and Duffy, Sandra and Heydenreich, Matthias and Muiva-Mutisya, Lois and Avery, Vicky M. and Erdelyi, Mate and Yenesew, Abiy}, title = {Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata}, series = {Molecules}, volume = {22}, journal = {Molecules}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules22020318}, pages = {11}, year = {2017}, abstract = {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.}, language = {en} } @misc{EndesfelderWeicheltStraussetal.2017, author = {Endesfelder, Stefanie and Weichelt, Ulrike and Strauß, Evelyn and Schl{\"o}r, Anja and Sifringer, Marco and Scheuer, Till and B{\"u}hrer, Christoph and Schmitz, Thomas}, title = {Neuroprotection by caffeine in hyperoxia-induced neonatal brain injury}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1097}, issn = {1866-8372}, doi = {10.25932/publishup-47504}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-475040}, pages = {26}, year = {2017}, abstract = {Sequelae of prematurity triggered by oxidative stress and free radical-mediated tissue damage have coined the term "oxygen radical disease of prematurity". Caffeine, a potent free radical scavenger and adenosine receptor antagonist, reduces rates of brain damage in preterm infants. In the present study, we investigated the effects of caffeine on oxidative stress markers, anti-oxidative response, inflammation, redox-sensitive transcription factors, apoptosis, and extracellular matrix following the induction of hyperoxia in neonatal rats. The brain of a rat pups at postnatal Day 6 (P6) corresponds to that of a human fetal brain at 28-32 weeks gestation and the neonatal rat is an ideal model in which to investigate effects of oxidative stress and neuroprotection of caffeine on the developing brain. Six-day-old Wistar rats were pre-treated with caffeine and exposed to 80\% oxygen for 24 and 48 h. Caffeine reduced oxidative stress marker (heme oxygenase-1, lipid peroxidation, hydrogen peroxide, and glutamate-cysteine ligase catalytic subunit (GCLC)), promoted anti-oxidative response (superoxide dismutase, peroxiredoxin 1, and sulfiredoxin 1), down-regulated pro-inflammatory cytokines, modulated redox-sensitive transcription factor expression (Nrf2/Keap1, and NF kappa B), reduced pro-apoptotic effectors (poly (ADP-ribose) polymerase-1 (PARP-1), apoptosis inducing factor (AIF), and caspase-3), and diminished extracellular matrix degeneration (matrix metalloproteinases (MMP) 2, and inhibitor of metalloproteinase (TIMP) 1/2). Our study affirms that caffeine is a pleiotropic neuroprotective drug in the developing brain due to its anti-oxidant, anti-inflammatory, and anti-apoptotic properties.}, language = {en} } @misc{YarmanJetzschmannNeumannetal.2017, author = {Yarman, Aysu and Jetzschmann, Katharina J. and Neumann, Bettina and Zhang, Xiaorong and Wollenberger, Ulla and Cordin, Aude and Haupt, Karsten and Scheller, Frieder W.}, title = {Enzymes as tools in MIP-sensors}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1098}, issn = {1866-8372}, doi = {10.25932/publishup-47464}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-474642}, pages = {18}, year = {2017}, abstract = {Molecularly imprinted polymers (MIPs) have the potential to complement antibodies in bioanalysis, are more stable under harsh conditions, and are potentially cheaper to produce. However, the affinity and especially the selectivity of MIPs are in general lower than those of their biological pendants. Enzymes are useful tools for the preparation of MIPs for both low and high-molecular weight targets: As a green alternative to the well-established methods of chemical polymerization, enzyme-initiated polymerization has been introduced and the removal of protein templates by proteases has been successfully applied. Furthermore, MIPs have been coupled with enzymes in order to enhance the analytical performance of biomimetic sensors: Enzymes have been used in MIP-sensors as tracers for the generation and amplification of the measuring signal. In addition, enzymatic pretreatment of an analyte can extend the analyte spectrum and eliminate interferences.}, language = {en} } @article{AdebayoHashimHassetal.2017, author = {Adebayo, Segun Emmanuel and Hashim, Norhashila and Hass, Roland and Reich, Oliver and Regen, Christian and M{\"u}nzberg, Marvin and Abdan, Khalina and Hanafi, Marsyita and Zude-Sasse, Manuela}, title = {Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear}, series = {Postharvest Biology and Technology}, volume = {130}, journal = {Postharvest Biology and Technology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-5214}, doi = {10.1016/j.postharvbio.2017.04.004}, pages = {56 -- 63}, year = {2017}, abstract = {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.}, language = {en} } @misc{HassSandmannReich2017, author = {Hass, Roland and Sandmann, Michael and Reich, Oliver}, title = {Photonic sensing in highly concentrated biotechnical processes by photon density wave spectroscopy}, series = {Proceedings SPIE 10323, 25th International Conference on Optical Fiber Sensors}, volume = {10323}, journal = {Proceedings SPIE 10323, 25th International Conference on Optical Fiber Sensors}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5090-4850-2}, issn = {0277-786X}, doi = {10.1117/12.2263617}, pages = {4}, year = {2017}, abstract = {Photon Density Wave (PDW) spectroscopy is introduced as a new approach for photonic sensing in highly concentrated biotechnical processes. It independently quantifies the absorption and reduced scattering coefficient calibration-free and as a function of time, thus describing the optical properties in the vis/NIR range of the biomaterial during their processing. As examples of industrial relevance, enzymatic milk coagulation, beer mashing, and algae cultivation in photo bioreactors are discussed.}, language = {en} } @misc{NaolouRuehlLendlein2017, author = {Naolou, Toufik and R{\"u}hl, Eckart and Lendlein, Andreas}, title = {Nanocarriers}, series = {European Journal of Pharmaceutics and Biopharmaceutics}, volume = {116}, journal = {European Journal of Pharmaceutics and Biopharmaceutics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0939-6411}, doi = {10.1016/j.ejpb.2017.03.004}, pages = {1 -- 3}, year = {2017}, language = {en} } @article{UtechtPalmerKlamroth2017, author = {Utecht, Manuel Martin and Palmer, Richard E. and Klamroth, Tillmann}, title = {Quantum chemical approach to atomic manipulation of chlorobenzene on the Si(111)-7 x 7 surface}, series = {Physical review materials}, volume = {1}, journal = {Physical review materials}, number = {2}, publisher = {American Physical Society}, address = {College Park}, issn = {2475-9953}, doi = {10.1103/PhysRevMaterials.1.026001}, pages = {5}, year = {2017}, abstract = {We present a cluster model to describe the localization of hot charge carriers on the Si(111)-7 x 7 surface, which leads to (nonlocal) desorption of chlorobenzene molecules in scanning tunneling microscope (STM) manipulation experiments. The localized charge carriers are modeled by a small cluster. By means of quantum chemical calculations, this cluster model explains many experimental findings from STM manipulation. We show that the negative charge is mainly localized in the surface, while the positive one also resides on the molecule. Both resonances boost desorption: In the negative resonance the adatom is elevated; in the positive one the chemisorption bond between the silicon surface adatom and chlorobenzene is broken. We find normal modes promoting desorption matching experimental low-temperature activation energies for electron-and hole-induced desorption.}, language = {en} } @article{WolfHolzmeierWagneretal.2017, author = {Wolf, Thomas J. A. and Holzmeier, Fabian and Wagner, Isabella and Berrah, Nora and Bostedt, Christoph and Bozek, John and Bucksbaum, Phil and Coffee, Ryan and Cryan, James and Farrell, Joe and Feifel, Raimund and Martinez, Todd J. and McFarland, Brian and Mucke, Melanie and Nandi, Saikat and Tarantelli, Francesco and Fischer, Ingo and G{\"u}hr, Markus}, title = {Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra}, series = {Applied sciences}, volume = {7}, journal = {Applied sciences}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {2076-3417}, doi = {10.3390/app7070681}, pages = {11}, year = {2017}, abstract = {Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymines neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.}, language = {en} } @article{MeynersMertensWessigetal.2017, author = {Meyners, Christian and Mertens, Monique and Wessig, Pablo and Meyer-Almes, Franz-Josef}, title = {A Fluorescence-Lifetime-Based Binding Assay for Class IIa Histone Deacetylases}, series = {Chemistry - a European journal}, volume = {23}, journal = {Chemistry - a European journal}, number = {13}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201605140}, pages = {3107 -- 3116}, year = {2017}, abstract = {Class IIa histone deacetylases (HDACs) show extremely low enzymatic activity and no commonly accepted endogenous substrate is known today. Increasing evidence suggests that these enzymes exert their effect rather through molecular recognition of acetylated proteins and recruiting other proteins like HDAC3 to the desired target location. Accordingly, class IIa HDACs like bromodomains have been suggested to act as "Readers" of acetyl marks, whereas enzymatically active HDACs of class I or IIb are called "Erasers" to highlight their capability to remove acetyl groups from acetylated histones or other proteins. Small-molecule ligands of class IIa histone deacetylases (HDACs) have gained tremendous attention during the last decade and have been suggested as pharmaceutical targets in several indication areas such as cancer, Huntington's disease and muscular atrophy. Up to now, only enzyme activity assays with artificial chemically activated trifluoroacetylated substrates are in use for the identification and characterization of new active compounds against class IIa HDACs. Here, we describe the first binding assay for this class of HDAC enzymes that involves a simple mix-and-measure procedure and an extraordinarily robust fluorescence lifetime readout based on [1,3]dioxolo[4,5-f]benzodioxole-based ligand probes. The principle of the assay is generic and can also be transferred to class I HDAC8.}, language = {en} } @article{BoboneHilschStormetal.2017, author = {Bobone, Sara and Hilsch, Malte and Storm, Julian and Dunsing, Valentin and Herrmann, Andreas and Chiantia, Salvatore}, title = {Phosphatidylserine Lateral Organization Influences the Interaction of Influenza Virus Matrix Protein 1 with Lipid Membranes}, series = {Journal of virology}, volume = {91}, journal = {Journal of virology}, publisher = {American Society for Microbiology}, address = {Washington}, issn = {0022-538X}, doi = {10.1128/JVI.00267-17}, pages = {15}, year = {2017}, abstract = {Influenza A virus matrix protein 1 (M1) is an essential component involved in the structural stability of the virus and in the budding of new virions from infected cells. A deeper understanding of the molecular basis of virion formation and the budding process is required in order to devise new therapeutic approaches. We performed a detailed investigation of the interaction between M1 and phosphatidylserine (PS) (i.e., its main binding target at the plasma membrane [PM]), as well as the distribution of PS itself, both in model membranes and in living cells. To this end, we used a combination of techniques, including Forster resonance energy transfer (FRET), confocal microscopy imaging, raster image correlation spectroscopy, and number and brightness (N\&B) analysis. Our results show that PS can cluster in segregated regions in the plane of the lipid bilayer, both in model bilayers constituted of PS and phosphatidylcholine and in living cells. The viral protein M1 interacts specifically with PS-enriched domains, and such interaction in turn affects its oligomerization process. Furthermore, M1 can stabilize PS domains, as observed in model membranes. For living cells, the presence of PS clusters is suggested by N\&B experiments monitoring the clustering of the PS sensor lactadherin. Also, colocalization between M1 and a fluorescent PS probe suggest that, in infected cells, the matrix protein can specifically bind to the regions of PM in which PS is clustered. Taken together, our observations provide novel evidence regarding the role of PS-rich domains in tuning M1-lipid and M1-M1 interactions at the PM of infected cells. IMPORTANCE Influenza virus particles assemble at the plasma membranes (PM) of infected cells. This process is orchestrated by the matrix protein M1, which interacts with membrane lipids while binding to the other proteins and genetic material of the virus. Despite its importance, the initial step in virus assembly (i.e., M1-lipid interaction) is still not well understood. In this work, we show that phosphatidylserine can form lipid domains in physical models of the inner leaflet of the PM. Furthermore, the spatial organization of PS in the plane of the bilayer modulates M1-M1 interactions. Finally, we show that PS domains appear to be present in the PM of living cells and that M1 seems to display a high affinity for them.}, language = {en} } @article{ShainyanBelyakovSigolaevetal.2017, author = {Shainyan, Bagrat A. and Belyakov, Alexander V. and Sigolaev, Yurii F. and Khramov, Alexander N. and Kleinpeter, Erich}, title = {Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, number = {1}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02538}, pages = {461 -- 470}, year = {2017}, abstract = {The molecular structure and conformational preferences of 1-phenyl-1-X-1-silacyclohexanes C5H10Si(Ph,X) (X = F (3), Cl (4)) were studied by gas-phase electron diffraction, low-temperature NMR spectroscopy, and high-level quantum chemical calculations. In the gas phase only three (3) and two (4) stable conformers differing in the axial or equatorial location of the phenyl group and the angle of rotation about the Si-C-ph bond (axi and axo denote the Ph group lying in or out of the X-Si-C-ph plane) contribute to the equilibrium. In 3 the ratio Ph-eq:Ph-axo:Ph-axi is 40(12):55(24):5 and 64:20:16 by experiment and theory, respectively. In 4 the ratio Ph-eq:Ph-axo is 79(15):21(15) and 71:29 by experiment and theory (M06-2X calculations), respectively. The gas-phase electron diffraction parameters are in good agreement with those obtained from theory at the M06-2X/aug-ccPVTZ and MP2/aug-cc-pVTZ levels. Unlike the case for M06-2X, MP2 calculations indicate that 3-Ph-eq conformer lies 0.5 kcal/mol higher than the 3-Ph-axo, conformer. As follows from QTAIM analysis, the phenyl group is more stable when it is located in the axial position but produces destabilization of the silacyclohexane ring: By low temperature NMR spectroscopy the six-membered ring interconversion could be frozen, at 103 K and the present conformational equilibria of 3 and 4 could be determined. The ratio of the conformers is 3-Ph-eq:3-Ph-ax = (75-77):(23-25) and 4-Ph-eq:4-Ph-ax = 82:18.}, language = {en} } @article{EhlertKlamroth2017, author = {Ehlert, Christopher and Klamroth, Tillmann}, title = {The quest for best suited references for configuration interaction singles calculations of core excited states}, series = {Journal of computational chemistry : organic, inorganic, physical, biological}, volume = {38}, journal = {Journal of computational chemistry : organic, inorganic, physical, biological}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0192-8651}, doi = {10.1002/jcc.24531}, pages = {116 -- 126}, year = {2017}, abstract = {Near edge X-ray absorption fine structure (NEXAFS) simulations based on the conventional configuration interaction singles (CIS) lead to excitation energies, which are systematically blue shifted. Using a (restricted) open shell core hole reference instead of the Hartree Fock (HF) ground state orbitals improves (Decleva et al., Chem. Phys., 1992, 168, 51) excitation energies and the shape of the spectra significantly. In this work, we systematically vary the underlying SCF approaches, that is, based on HF or density functional theory, to identify best suited reference orbitals using a series of small test molecules. We compare the energies of the K edges and NEXAFS spectra to experimental data. The main improvement compared to conventional CIS, that is, using HF ground state orbitals, is due to the electrostatic influence of the core hole. Different SCF approaches, density functionals, or the use of fractional occupations lead only to comparably small changes. Furthermore, to account for bigger systems, we adapt the core-valence separation for our approach. We demonstrate that the good quality of the spectrum is not influenced by this approximation when used together with the non-separated ground state wave function. Simultaneously, the computational demands are reduced remarkably. (C) 2016 Wiley Periodicals, Inc.}, language = {en} } @article{vonKlitzingStehlPogrzebaetal.2017, author = {von Klitzing, Regine and Stehl, Dimitrij and Pogrzeba, Tobias and Schoma{\"a}cker, Reinhard and Minullina, Renata and Panchal, Abhishek and Konnova, Svetlana and Fakhrullin, Rawil and Koetz, Joachim and Moehwald, Helmuth and Lvov, Yuri}, title = {Halloysites Stabilized Emulsions for Hydroformylation of Long Chain Olefins}, series = {Advanced materials interfaces}, volume = {4}, journal = {Advanced materials interfaces}, number = {1}, publisher = {Wiley}, address = {Hoboken}, issn = {2196-7350}, doi = {10.1002/admi.201600435}, pages = {8}, year = {2017}, abstract = {Halloysites as tubular alumosilicates are introduced as inexpensive natural nanoparticles to form and stabilize oil-water emulsions. This stabilized emulsion is shown to enable efficient interfacial catalytic reactions. Yield, selectivity, and product separation can be tremendously enhanced, e.g., for the hydroformylation reaction of dodecene to tridecanal. In perspective, this type of formulation may be used for oil spill dispersions. The key elements of the described formulations are clay nanotubes (halloysites) which are highly anisometric, can be filled by helper molecules, and are abundantly available in thousands of tons, making this technology scalable for industrial applications.}, language = {en} } @article{SchweighoeferMorenoBoboneetal.2017, author = {Schweigh{\"o}fer, F. and Moreno, J. and Bobone, Sara and Chiantia, Salvatore and Herrmann, A. and Hecht, S. and Wachtveitl, Josef}, title = {Connectivity pattern modifies excited state relaxation dynamics of fluorophore-photoswitch molecular dyads}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c6cp07112k}, pages = {4010 -- 4018}, year = {2017}, abstract = {In order to modulate the emission of BODIPY fluorophores, they were connected to a diarylethene (DAE) photoswitch via phenylene-ethynylene linkers of different lengths and orientations. The latter allowed for modulation of the electronic coupling in the prepared four BODIPY-DAE dyads, which were compared also to appropriate BODIPY and DAE model compounds by steady state as well as time-resolved spectroscopies. In their open isomers, all dyads show comparable luminescence behavior indicative of an unperturbed BODIPY fluorophore. In strong contrast, in the closed isomers the BODIPY emission is efficiently quenched but the deactivation mechanism depends on the nature of the linker. The most promising dyad was rendered water-soluble by means of micellar encapsulation and aqueous suspensions were investigated by fluorescence spectroscopy and microscopy. Our results (i) illustrate that the electronic communication between the BODIPY and DAE units can indeed be fine-tuned by the nature of the linker to achieve fluorescence modulation while maintaining photoswitchability and (ii) highlight potential applications to image and control biological processes with high spatio-temporal resolution.}, language = {en} } @article{KellyRolandZhangetal.2017, author = {Kelly, Mary Allison and Roland, Steffen and Zhang, Qianqian and Lee, Youngmin and Kabius, Bernd and Wang, Qing and Gomez, Enrique D. and Neher, Dieter and You, Wei}, title = {Incorporating Fluorine Substitution into Conjugated Polymers for Solar Cells}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {121}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.6b10993}, pages = {2059 -- 2068}, year = {2017}, abstract = {Fluorinating conjugated polymers is a proven strategy for creating high performance materials in polymer solar cells, yet few studies have investigated the importance of the fluorination method. We compare the performance of three fluorinated systems: a poly(benzodithieno-dithienyltriazole) (PBnDT-XTAZ) random copolymer where 50\% of the acceptor units are difluorinated, PBnDT-mFTAZ where every acceptor unit is monofluorinated, and a 1:1 physical blend of the difluorinated and nonfluorinated polymer. All systems have the same degree of fluorination (50\%) yet via different methods (chemically vs physically, random vs regular). We show that these three systems have equivalent photovoltaic behavior:,similar to 5.2\% efficiency with a short-circuit current (J(sc)) at,similar to 11 mA cm(-2), an open-circuit voltage (v(oc)) at 0.77 V, and a fill factor (FF) of similar to 60\%. Further investigation of these three systems demonstrates that the charge generation, charge extraction, and charge transfer state are essentially identical for the three studied systems. Transmission electron microscopy shows no significant differences in the morphologies. All these data illustrate that it is possible to improve performance not only via regular or random fluorination but also by physical addition via a ternary blend. Thus, our results demonstrate the versatility of incorporating fluorine in the active layer of polymer solar cells to enhance device performance.}, language = {en} } @article{LippoldEidnerKumkeetal.2017, author = {Lippold, Holger and Eidner, Sascha and Kumke, Michael Uwe and Lippmann-Pipke, Johanna}, title = {Dynamics of metal-humate complexation equilibria as revealed by isotope exchange studies - a matter of concentration and time}, series = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society}, volume = {197}, journal = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society}, publisher = {Elsevier}, address = {Oxford}, issn = {0016-7037}, doi = {10.1016/j.gca.2016.10.019}, pages = {62 -- 70}, year = {2017}, abstract = {Complexation with dissolved humic matter can be crucial in controlling the mobility of toxic or radioactive contaminant metals. For speciation and transport modelling, a dynamic equilibrium process is commonly assumed, where association and dissociation run permanently. This is, however, questionable in view of reported observations of a growing resistance to dissociation over time. In this study, the isotope exchange principle was employed to gain direct insight into the dynamics of the complexation equilibrium, including kinetic inertisation phenomena. Terbium(III), an analogue of trivalent actinides, was used as a representative of higher-valent metals. Isotherms of binding to (flocculated) humic acid, determined by means of Tb-160 as a radiotracer, were found to be identical regardless of whether the radioisotope was introduced together with the bulk of stable Tb-159 or subsequently after pre-equilibration for up to 3 months. Consequently, there is a permanent exchange of free and humic-bound Tb since all available binding sites are occupied in the plateau region of the isotherm. The existence of a dynamic equilibrium was thus evidenced. There was no indication of an inertisation under these experimental conditions. If the small amount of Tb-160 was introduced prior to saturation with Tb-159, the expected partial desorption of Tb-160 occurred at much lower rates than observed for the equilibration process in the reverse procedure. In addition, the rates decreased with time of pre-equilibration. Inertisation phenomena are thus confined to the stronger sites of humic molecules (occupied at low metal concentrations). Analysing the time-dependent course of isotope exchange according to first-order kinetics indicated that up to 3 years are needed to attain equilibrium. Since, however, metal-humic interaction remains reversible, exchange of metals between humic carriers and mineral surfaces cannot be neglected on the long time scale to be considered in predictive transport models.}, language = {en} } @article{MichalikOnichimowskaBeitzPanneetal.2017, author = {Michalik-Onichimowska, Aleksandra and Beitz, Toralf and Panne, Ulrich and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Riedel, Jens}, title = {Microsecond mid-infrared laser pulses for atmospheric pressure laser ablation/ionization of liquid samples}, series = {Sensors and actuators : B, Chemical}, volume = {238}, journal = {Sensors and actuators : B, Chemical}, publisher = {Elsevier}, address = {Lausanne}, issn = {0925-4005}, doi = {10.1016/j.snb.2016.06.155}, pages = {298 -- 305}, year = {2017}, abstract = {In many laser based ionization techniques with a subsequent drift time separation, the laser pulse generating the ions is considered as the start time to. Therefore, an accurate temporal definition of this event is crucial for the resolution of the experiments. In this contribution, the laser induced plume dynamics of liquids evaporating into atmospheric pressure are visualized for two distinctively different laser pulse widths, Delta t = 6 nanoseconds and Delta tau = 280 microseconds. For ns-pulses the expansion of the generated vapour against atmospheric pressure is found to lead to turbulences inside the gas phase. This results in spatial and temporal broadening of the nascent clouds. A more equilibrated expansion, without artificial smearing of the temporal resolution can, in contrast, be observed to follow mu s-pulse excitation. This leads to the counterintuitive finding that longer laser pulses results in an increased temporal vapour formation definition. To examine if this fume expansion also eventually results in a better definition of ion formation, the nascent vapour plumes were expanded into a linear drift tube ion mobility spectrometer (IMS). This time resolved detection of ion formation corroborates the temporal broadening caused by collisional impeding of the supersonic expansion at atmospheric pressure and the overall better defined ion formation by evaporation with long laser pulses. A direct comparison of the observed results strongly suggests the coexistence of two individual ion formation mechanisms that can be specifically addressed by the use of appropriate laser sources.}, language = {en} } @article{RumschoettelBausKosmellaetal.2017, author = {Rumsch{\"o}ttel, Jens and Baus, Susann and Kosmella, Sabine and Appelhans, Dietmar and Koetz, Joachim}, title = {Incorporation of DNA/PEI polyplexes into gelatin/chitosan hydrogel scaffolds}, series = {Composite interfaces}, volume = {25}, journal = {Composite interfaces}, number = {1}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1568-5543}, doi = {10.1080/09276440.2017.1302725}, pages = {1 -- 11}, year = {2017}, abstract = {Polyplexes between a double-stranded Salmon DNA and hyperbranched poly(ethyleneimine) (PEI) as well as a maltosylated PEI-Mal were incorporated into a gelatin/chitosan hydrogel scaffold. Calorimetric experiments of the polyplexes show a decrease of the melting temperature in presence of PEI and a peak splitting in presence of PEI-Mal, which can be interpreted to a partial compaction of the DNA strands in presence of PEI-Mal. When the polyplexes are incorporated into a gelatin/chitosan scaffold in the swollen state, the DNA melting peaks at 90 and 93 degrees C, respectively, indicate in both cases the release of the DNA at the surface of the hydrogel scaffold in a more compact form. Specific interactions between the PEI-Mal shell and gelatin are responsible for the tuning of the release properties in presence of the maltose units in the hyperbranched PEI.}, language = {en} } @article{ZuehlkeSassRiebeetal.2017, author = {Z{\"u}hlke, Martin and Sass, Stephan and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Real-Time Reaction Monitoring of an Organic Multistep Reaction by Electrospray Ionization-Ion Mobility Spectrometry}, series = {ChemPlusChem}, volume = {82}, journal = {ChemPlusChem}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2192-6506}, doi = {10.1002/cplu.201700296}, pages = {1266 -- 1273}, year = {2017}, abstract = {The capability of electrospray ionization (ESI)-ion mobility (IM) spectrometry for reaction monitoring is assessed both as a stand-alone real-time technique and in combination with HPLC. A three-step chemical reaction, consisting of a Williamson ether synthesis followed by a hydrogenation and an N-alkylation step, is chosen for demonstration. Intermediates and products are determined with a drift time to mass-per-charge correlation. Addition of an HPLC column to the setup increases the separation power and allows the determination of further species. Monitoring of the intensities of the various species over the reaction time allows the detection of the end of reaction, determination of the rate-limiting step, observation of the system response in discontinuous processes, and optimization of the mass ratios of the starting materials. However, charge competition in ESI influences the quantitative detection of substances in the reaction mixture. Therefore, two different methods are investigated, which allow the quantification and investigation of reaction kinetics. The first method is based on the pre-separation of the compounds on an HPLC column and their subsequent individual detection in the ESI-IM spectrometer. The second method involves an extended calibration procedure, which considers charge competition effects and facilitates nearly real-time quantification.}, language = {en} } @article{ParamonovKuehnBandrauk2017, author = {Paramonov, Guennaddi K. and K{\"u}hn, Oliver and Bandrauk, Andr{\´e} D.}, title = {Excitation of H+ 2 with one-cycle laser pulses}, series = {Molecular physics : MP ; an international journal in the field of chemical physics}, volume = {115}, journal = {Molecular physics : MP ; an international journal in the field of chemical physics}, number = {15/16}, publisher = {Taylor \& Francis}, address = {London}, issn = {0026-8976}, doi = {10.1080/00268976.2017.1288938}, pages = {1846 -- 1860}, year = {2017}, abstract = {Non-Born-Oppenheimer quantum dynamics of H+ 2 excited by shaped one-cycle laser pulses linearly polarised along the molecular axis have been studied by the numerical solution of the time-dependent Schr{\"o}dinger equation within a three-dimensional model, including the internuclear separation, R, and the electron coordinates z and ρ. Laser carrier frequencies corresponding to the wavelengths λ l = 25 nm through λ l = 400 nm were used and the amplitudes of the pulses were chosen such that the energy of H+ 2 was close to its dissociation threshold at the end of any laser pulse applied. It is shown that there exists a characteristic oscillation frequency ωosc ≃ 0.2265 au (corresponding to the period of τosc ≃ 0.671 fs and the wavelength of λosc ≃ 201 nm) that manifests itself as a 'carrier' frequency of temporally shaped oscillations of the time-dependent expectation values ⟨z ⟩ and ⟨∂V/∂z ⟩ that emerge at the ends of the laser pulses and exist on a timescale of at least 50 fs. Time-dependent expectation values ⟨ρ⟩ and ⟨∂V /∂ρ⟩ of the optically passive degree of freedom, ρ, demonstrate post-laser-field oscillations at two basic frequencies ωρ 1 ≈ ωosc and ωρ 2 ≈ 2ωosc. Power spectra associated with the electronic motion show higher- and lower-order harmonics with respect to the driving field.}, language = {en} } @article{PloetzMegowNiehausetal.2017, author = {Pl{\"o}tz, Per-Arno and Megow, J{\"o}rg and Niehaus, Thomas and K{\"u}hn, Oliver}, title = {Spectral densities for Frenkel exciton dynamics in molecular crystals}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {146}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4976625}, pages = {10}, year = {2017}, abstract = {Effects of thermal fluctuations on the electronic excitation energies and intermonomeric Coulomb couplings are investigated for a perylene-tetracarboxylic-diimidecrystal. To this end, time dependent density functional theory based tight binding (TD-DFTB) in the linear response formulation is used in combination with electronic ground state classical molecular dynamics. As a result, a parametrized Frenkel exciton Hamiltonian is obtained, with the effect of exciton-vibrational coupling being described by spectral densities. Employing dynamically defined normal modes, these spectral densities are analyzed in great detail, thus providing insight into the effect of specific intramolecular motions on excitation energies and Coulomb couplings. This distinguishes the present method from approaches using fixed transition densities. The efficiency by which intramolecular contributions to the spectral density can be calculated is a clear advantage of this method as compared with standard TD-DFT. Published by AIP Publishing.}, language = {en} } @phdthesis{You2017, author = {You, Zewang}, title = {Conformational transition of peptide-functionalized cryogels enabling shape-memory capability}, school = {Universit{\"a}t Potsdam}, pages = {144}, year = {2017}, language = {en} } @article{MuthauraKerikoMutaietal.2017, author = {Muthaura, Charles N. and Keriko, Joseph M. and Mutai, Charles and Yenesew, Abiy and Heydenreich, Matthias and Atilaw, Yoseph and Gathirwa, Jeremiah W. and Irungu, Beatrice N. and Derese, Solomon}, title = {Antiplasmodial, cytotoxicity and phytochemical constituents of four maytenus species used in traditional medicine in Kenya}, series = {The natural products journal}, volume = {7}, journal = {The natural products journal}, number = {2}, publisher = {Bentham Science Publ.}, address = {Sharjah}, issn = {2210-3155}, doi = {10.2174/2210315507666161206144050}, pages = {144 -- 152}, year = {2017}, abstract = {Background: In Kenya, several species of the genus Maytenus are used in traditional medicine to treat many diseases including malaria. In this study, phytochemical constituents and extracts of Maytenus undata, M. putterlickioides, M. senegalensis and M. heterophylla were evaluated to determine compound/s responsible for antimalarial activity. Objective: To isolate antiplasmodial compounds from these plant species which could be used as marker compounds in the standardization of their extracts as a phytomedicine for malaria. Methods: Constituents were isolated through activity-guided fractionation of the MeOH/CHCl3 (1:1) extracts and in vitro inhibition of Plasmodium falciparum. Cytotoxicity was evaluated using Vero cells and the compounds were elucidated on the basis of NMR spectroscopy. Results: Fractionation of the extracts resulted in the isolation of ten known compounds. Compound 1 showed promising antiplasmodial activity with IC50, 3.63 and 3.95 ng/ml against chloroquine sensitive (D6) and resistant (W2) P. falciparum, respectively and moderate cytotoxicity (CC50, 37.5 ng/ml) against Vero E6 cells. The other compounds showed weak antiplasmodial (IC50 > 1.93 mu g/ml) and cytotoxic (CC50 > 39.52 mu g/ml) activities against P. falciparum and Vero E6 cells, respectively. Conclusion: (20 alpha)-3-hydroxy-2-oxo-24-nor-friedela-1(10),3,5,7-tetraen-carboxylic acid-(29)-methyl-ester (pristimerin) (1) was the most active marker and lead compound that warrants further investigation as a template for the development of new antimalarial drugs. Pristimerin is reported for the first time in M. putterlickioides. 3-Hydroxyolean-12-en-28-oic acid (oleanolic acid) (5), stigmast-5-en-3-ol (beta-sitosterol) (6), 3-oxo-28-friedelanoic acid (7), olean-12-en-3-ol (beta-amyrin) (8), lup-20(29)-en-3-ol (lupeol) (9) and lup-20(29)-en-3-one (lupenone) (10) are reported for the first time in M. undata.}, language = {en} } @phdthesis{Schulze2017, author = {Schulze, Nicole}, title = {Neue Templatphasen zur anisotropen Goldnanopartikelherstellung durch den Einsatz strukturbildender Polymere}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-409515}, school = {Universit{\"a}t Potsdam}, pages = {VI, 117, xv}, year = {2017}, abstract = {Ziel der vorliegenden Arbeit war die Synthese und Charakterisierung von anisotropen Goldnanopartikeln in einer geeigneten Polyelektrolyt-modifizierten Templatphase. Der Mittelpunkt bildet dabei die Auswahl einer geeigneten Templatphase, zur Synthese von einheitlichen und reproduzierbaren anisotropen Goldnanopartikeln mit den daraus resultierenden besonderen Eigenschaften. Bei der Synthese der anisotropen Goldnanopartikeln lag der Fokus in der Verwendung von Vesikeln als Templatphase, wobei hier der Einfluss unterschiedlicher strukturbildender Polymere (stark alternierende Maleamid-Copolymere PalH, PalPh, PalPhCarb und PalPhBisCarb mit verschiedener Konformation) und Tenside (SDS, AOT - anionische Tenside) bei verschiedenen Synthese- und Abtrennungsbedingungen untersucht werden sollte. Im ersten Teil der Arbeit konnte gezeigt werden, dass PalPhBisCarb bei einem pH-Wert von 9 die Bedingungen eines R{\"o}hrenbildners f{\"u}r eine morphologische Transformation von einer vesikul{\"a}ren Phase in eine r{\"o}hrenf{\"o}rmige Netzwerkstruktur erf{\"u}llt und somit als Templatphase zur formgesteuerten Bildung von Nanopartikeln genutzt werden kann. Im zweiten Teil der Arbeit wurde dargelegt, dass die Templatphase PalPhBisCarb (pH-Wert von 9, Konzentration von 0,01 wt.\%) mit AOT als Tensid und PL90G als Phospholipid (im Verh{\"a}ltnis 1:1) die effektivste Wahl einer Templatphase f{\"u}r die Bildung von anisotropen Strukturen in einem einstufigen Prozess darstellt. Bei einer konstanten Synthesetemperatur von 45 °C wurden die besten Ergebnisse bei einer Goldchloridkonzentration von 2 mM, einem Gold-Templat-Verh{\"a}ltnis von 3:1 und einer Synthesezeit von 30 Minuten erzielt. Ausbeute an anisotropen Strukturen lag bei 52 \% (Anteil an dreieckigen Nanopl{\"a}ttchen von 19 \%). Durch Erh{\"o}hung der Synthesetemperatur konnte die Ausbeute auf 56 \% (29 \%) erh{\"o}ht werden. Im dritten Teil konnte durch zeitabh{\"a}ngige Untersuchungen gezeigt werden, dass bei Vorhandensein von PalPhBisCarb die Bildung der energetisch nicht bevorzugten Pl{\"a}ttchen-Strukturen bei Raumtemperatur initiiert wird und bei 45 °C ein Optimum annimmt. Kintetische Untersuchungen haben gezeigt, dass die Bildung dreieckiger Nanopl{\"a}ttchen bei schrittweiser Zugabe der Goldchlorid-Pr{\"a}kursorl{\"o}sung zur PalPhBisCarb enthaltenden Templatphase durch die Dosierrate der vesikul{\"a}ren Templatphase gesteuert werden kann. In umgekehrter Weise findet bei Zugabe der Templatphase zur Goldchlorid-Pr{\"a}kursorl{\"o}sung bei 45 °C ein {\"a}hnlicher, kinetisch gesteuerter Prozess der Bildung von Nanodreiecken statt mit einer maximalen Ausbeute dreieckigen Nanopl{\"a}ttchen von 29 \%. Im letzten Kapitel erfolgten erste Versuche zur Abtrennung dreieckiger Nanopl{\"a}ttchen von den {\"u}brigen Geometrien der gemischten Nanopartikell{\"o}sung mittels tensidinduzierter Verarmungsf{\"a}llung. Bei Verwendung von AOT mit einer Konzentration von 0,015 M wurde eine Ausbeute an Nanopl{\"a}ttchen von 99 \%, wovon 72 \% dreieckiger Geometrien hatten, erreicht.}, language = {de} } @phdthesis{Firkala2017, author = {Firkala, Tam{\´a}s}, title = {Investigation of nanoparticle-molecule interactions and pharmaceutical model formulations by means of surface enhanced raman spectroscopy}, school = {Universit{\"a}t Potsdam}, pages = {118}, year = {2017}, language = {en} } @phdthesis{Stephan2017, author = {Stephan, Florian}, title = {Mehrfachintegration von Experimenten im Chemielehrgang}, school = {Universit{\"a}t Potsdam}, pages = {123}, year = {2017}, language = {de} } @phdthesis{LorenteSanchez2017, author = {Lorente S{\´a}nchez, Alejandro Jose}, title = {Synthesis of side-chain polystyrenes for all organic solution processed OLEDs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-398006}, school = {Universit{\"a}t Potsdam}, pages = {xiv, 131}, year = {2017}, abstract = {In the present work side-chain polystyrenes were synthesized and characterized, in order to be applied in multilayer OLEDs fabricated by solution process techniques. Manufacture of optoelectronic devices by solution process techniques is meant to decrease significantly fabrication cost and allow large scale production of such devices. This dissertation focusses in three series, enveloped in two material classes. The two classes differ to each other in the type of charge transport exhibited, either ambipolar transport or electron transport. All materials were applied in all-organic solution processed green Ir-based devices. In the first part, a series of ambipolar host materials were developed to transport both charge types, holes and electrons, and be applied especially as matrix for green Ir-based emitters. It was possible to increase devices efficacy by modulating the predominant charge transport type. This was achieved by modification of molecules electron transport part with more electron-deficient heterocycles or by extending the delocalization of the LUMO. Efficiencies up to 28.9 cd/A were observed for all-organic solution-process three layer devices. In the second part, suitability of triarylboranes and tetraphenylsilanes as electron transport materials was studied. High triplet energies were obtained, up to 2.95 eV, by rational combination of both molecular structures. Although the combination of both elements had a low effect in materials electron transport properties, high efficiencies around 24 cd/A were obtained for the series in all-organic solution-processed two layer devices. In the last part, benzene and pyridine were chosen as the series electron-transport motif. By controlling the relative pyridine content (RPC) solubility into methanol was induced for polystyrenes with bulky side-chains. Materials with RPC ≥ 0.5 could be deposited orthogonally from solution without harming underlying layers. From the best of our knowledge, this is the first time such materials are applied in this architecture showing moderate efficiencies around 10 cd/A in all-organic solution processed OLEDs. Overall, the outcome of these studies will actively contribute to the current research on materials for all-solution processed OLEDs.}, language = {en} } @phdthesis{Dippel2017, author = {Dippel, Sandor}, title = {Development of functional hydrogels for sensor applications}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-398252}, school = {Universit{\"a}t Potsdam}, pages = {127}, year = {2017}, abstract = {In this work, a sensor system based on thermoresponsive materials is developed by utilizing a modular approach. By synthesizing three different key monomers containing either a carboxyl, alkene or alkyne end group connected with a spacer to the methacrylic polymerizable unit, a flexible copolymerization strategy has been set up with oligo ethylene glycol methacrylates. This allows to tune the lower critical solution temperature (LCST) of the polymers in aqueous media. The molar masses are variable thanks to the excurse taken in polymerization in ionic liquids thus stretching molar masses from 25 to over 1000 kDa. The systems that were shown shown to be effective in aqueous solution could be immobilized on surfaces by copolymerizing photo crosslinkable units. The immobilized systems were formulated to give different layer thicknesses, swelling ratios and mesh sizes depending on the demand of the coupling reaction. The coupling of detector units or model molecules is approached via reactions of the click chemistry pool, and the reactions are evaluated on their efficiency under those aspects, too. These coupling reactions are followed by surface plasmon resonance spectroscopy (SPR) to judge efficiency. With these tools at hand, Salmonella saccharides could be selectively detected by SPR. Influenza viruses were detected in solution by turbidimetry in solution as well as by a copolymerized solvatochromic dye to track binding via the changes of the polymers' fluorescence by said binding event. This effect could also be achieved by utilizing the thermoresponsive behavior. Another demonstrator consists of the detection system bound to a quartz surface, thus allowing the virus detection on a solid carrier. The experiments show the great potential of combining the concepts of thermoresponsive materials and click chemistry to develop technically simple sensors for large biomolecules and viruses.}, language = {en} } @phdthesis{John2017, author = {John, Daniela}, title = {Herstellung anisotroper Kolloide mittels templatgesteuerter Assemblierung und Kontaktdruckverfahren}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-398270}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 122, XVII}, year = {2017}, abstract = {Diese Arbeit befasste sich mit neuen Konzepten zur Darstellung anisotroper Partikelsysteme durch Anordnung von funktionalisierten Partikeln unter Zuhilfenahme etablierter Methoden wie der templatgest{\"u}tzten Assemblierung von Partikeln und dem Mikrokontaktdruck. Das erste Teilprojekt besch{\"a}ftigte sich mit der kontrollierten Herstellung von Faltenstrukturen im Mikro- bis Nanometerbereich. Die Faltenstrukturen entstehen durch die Relaxation eines Systems bestehend aus zwei {\"u}bereinander liegender Schichten unterschiedlicher Elastizit{\"a}t. In diesem Fall wurden Falten auf einem elastischen PDMS-Substrat durch Generierung einer Oxidschicht auf der Substratoberfl{\"a}che mittels Plasmabehandlung erzeugt. Die Dicke der Oxidschicht, die {\"u}ber verschiedene Parameter wie Behandlungszeit, Prozessleistung, Partialdruck des plasmaaktiven Gases, Vernetzungsgrad, Deformation sowie Substratdicke einstellbar war, bestimmte Wellenl{\"a}nge und Amplitude der Falten. Das zweite Teilprojekt hatte die Darstellung komplexer, kolloidaler Strukturen auf Basis supramolekularer Wechselwirkungen zum Ziel. Dazu sollte vor allem die templatgest{\"u}tzte Assemblierung von Partikeln sowohl an fest-fl{\"u}ssig als auch fl{\"u}ssig-fl{\"u}ssig Grenzfl{\"a}chen genutzt werden. F{\"u}r Erstere sollten die in Teilprojekt 1 hergestellten Faltenstrukturen als Templat, f{\"u}r Letztere Pickering-Emulsionen zur Anwendung kommen. Im ersten Fall wurden verschiedene, modifizierte Silicapartikel und Magnetitnanopartikel, deren Gr{\"o}ße und Oberfl{\"a}chenfunktionalit{\"a}t (Cyclodextrin-, Azobenzol- und Arylazopyrazolgruppen) variierte, in Faltenstrukturen angeordnet. Die Anordnung hing dabei nicht nur vom gew{\"a}hlten Verfahren, sondern auch von Faktoren wie der Partikelkonzentration, der Oberfl{\"a}chenladung oder dem Gr{\"o}ßenverh{\"a}ltnis der Partikel zur Faltengeometrie ab. Die Kombination von Cyclodextrin (CD)- und Arylazopyrazol-modifizierten Partikeln erm{\"o}glichte, auf Basis einer Wirt-Gast-Wechselwirkung zwischen den Partikeltypen und einer templatgesteuerten Anordnung, die Bildung komplexer und strukturierter Formen in der Gr{\"o}ßenordnung mehrerer Mikrometer. Dieses System kann einerseits als Grundlage f{\"u}r die Herstellung verschiedener Janus-Partikel herangezogen werden, andererseits stellt die gerichtete Vernetzung zweier Partikelsysteme zu gr{\"o}ßeren Aggregaten den Grundstein f{\"u}r neuartige, funktionale Materialien dar. Neben der Anordnung an fest-fl{\"u}ssig Grenzfl{\"a}chen konnte außerdem nachgewiesen werden, dass Azobenzol-funktionalisierte Silicapartikel in der Lage sind, Pickering-Emulsionen {\"u}ber mehrere Monate zu stabilisieren. Die Stabilit{\"a}t und Gr{\"o}ße der Emulsionsphase kann {\"u}ber Parameter, wie das Volumenverh{\"a}ltnis und die Konzentration, gesteuert werden. CD-funktionalisierte Silicapartikel besaßen dagegen keine Grenzfl{\"a}chenaktivit{\"a}t, w{\"a}hrend es CD-basierten Polymeren wiederum m{\"o}glich war, durch die Ausbildung von Einschlusskomplexen mit den hydrophoben Molek{\"u}len der {\"O}lphase stabile Emulsionen zu bilden. Dagegen zeigte die Kombination zwei verschiedener Partikelsysteme keinen oder einen destabilisierenden Effekt bez{\"u}glich der Ausbildung von Emulsionen. Im letzten Teilprojekt wurde die Herstellung multivalenter Silicapartikel mittels Mikrokontaktdruck untersucht. Die Faltenstrukturen wurden dabei als Stempel verwendet, wodurch es m{\"o}glich war, die Patch-Geometrie {\"u}ber die Wellenl{\"a}nge der Faltenstrukturen zu steuern. Als Tinte diente das positiv geladene Polyelektrolyt Polyethylenimin (PEI), welches {\"u}ber elektrostatische Wechselwirkungen auf unmodifizierten Silicapartikeln haftet. Im Gegensatz zum Drucken mit flachen Stempeln fiel dabei zun{\"a}chst auf, dass sich die Tinte bei den Faltenstrukturen nicht gleichm{\"a}ßig {\"u}ber die gesamte Substratfl{\"a}che verteilt, sondern haupts{\"a}chlich in den Faltent{\"a}lern vorlag. Dadurch handelte es sich bei dem Druckprozess letztlich nicht mehr um ein klassisches Mikrokontaktdruckverfahren, sondern um ein Tiefdruckverfahren. {\"U}ber das Tiefdruckverfahren war es dann aber m{\"o}glich, sowohl eine als auch beide Partikelhemisph{\"a}ren gleichzeitig und mit verschiedenen Funktionalit{\"a}ten zu modifizieren und somit multivalente Silicapartikel zu generieren. In Abh{\"a}ngigkeit der Wellenl{\"a}nge der Falten konnten auf einer Partikelhemisph{\"a}re zwei bis acht Patches abgebildet werden. F{\"u}r die Patch-Geometrie, sprich Gr{\"o}ße und Form der Patches, spielten zudem die Konzentration der Tinte auf dem Stempel, das L{\"o}sungsmittel zum Abl{\"o}sen der Partikel nach dem Drucken sowie die Stempelh{\"a}rte eine wichtige Rolle. Da die Stempelh{\"a}rte aufgrund der variierenden Dicke der Oxidschicht bei verschiedenen Wellenl{\"a}ngen nicht kontant ist, wurden f{\"u}r den Druckprozess meist Abg{\"u}sse der Faltensubstrate verwendet. Auf diese Weise war auch die Vergleichbarkeit bei variierender Wellenl{\"a}nge gew{\"a}hrleistet. Neben dem erfolgreichen Nachweis der Modifikation mittels Tiefdruckverfahren konnte auch gezeigt werden, dass {\"u}ber die Komplexierung mit PEI negativ geladene Nanopartikel auf die Partikeloberfl{\"a}che aufgebracht werden k{\"o}nnen.}, language = {de} } @misc{MirskovaAdamovichMirskovetal.2017, author = {Mirskova, Anna N. and Adamovich, Sergey N. and Mirskov, Rudolf G. and Schilde, Uwe}, title = {Reaction of pharmacological active tris-(2-hydroxyethyl)ammonium 4-chlorophenylsulfanylacetate with ZnCl2 or NiCl2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-401099}, pages = {5}, year = {2017}, abstract = {The reaction of pharmacological active protic ionic liquid tris-(2-hydroxyethyl)ammonium 4-chlorophenylsulfanylacetate H + N(CH 2 CH 2 OH) 3 ∙ ( - OOCCH 2 SC 6 H 4 Cl-4) (1) with zinc or nickel chloride in a ratio of 2:1 affords stable at room temperature powder-like adducts [H + N(CH 2 CH 2 OH) 3 ] 2 ∙ [M(OOCCH 2 SC 6 H 4 Cl-4) 2 Cl 2 ] 2- , M = Zn (2), Ni (3). By recrystallization from aqueous alcohol compound 2 unexpectedly gives Zn(OOCCH 2 SC 6 H 4 Cl-4) 2 ∙ 2H 2 O (4). Unlike 2, compound 3 gives crystals [N(CH 2 CH 2 OH) 3 ] 2 Ni 2+ · [ - OOCCH 2 SC 6 H 4 Cl-4] 2 (5), which have a structure of metallated ionic liquid. The structure of 5 has been proved by X-ray diffraction analysis. It is the first example of the conversion of a protic ionic liquid into potentially biological active metallated ionic liquid (1 → 3 → 5).}, language = {en} } @article{SchildePazOrtiz2017, author = {Schilde, Uwe and Paz, Christian and Ortiz, Leandro}, title = {Crystal structure of erioflorin isolated from Podanthus mitiqui (L.)}, series = {Acta Crystallographica Section E : Crystallographic Communications}, volume = {73}, journal = {Acta Crystallographica Section E : Crystallographic Communications}, number = {3}, publisher = {International Union of Crystallography}, address = {Chester}, doi = {10.1107/S2056989017001700}, pages = {334 -- 337}, year = {2017}, abstract = {The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a, 2,3,5a, 7,8,8a, 9,10,10a-decahydro-3-hydroxy-4,10a-dimethyl-8-methylidene-7-oxooxireno[5,6] cyclodeca[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P2(1)2(1)2(1), and its molecular structure consists of a methacrylic ester of a ten-membered ring sesquiterpenoid annelated with an epoxide and a butyrolactone. The structure is stabilized by one intramolecular C-H center dot center dot center dot O hydrogen bond. An O-H center dot center dot center dot O hydrogen bond and further C-H center dot center dot center dot O interactions can be observed in the packing.}, language = {en} } @misc{SchildePazOrtiz2017, author = {Schilde, Uwe and Paz, Christian and Ortiz, Leandro}, title = {Crystal structure of erioflorin isolated from Podanthus mitiqui (L.)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-401832}, pages = {4}, year = {2017}, abstract = {The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a, 2,3,5a, 7,8,8a, 9,10,10a-decahydro-3-hydroxy-4,10a-dimethyl-8-methylidene-7-oxooxireno[5,6] cyclodeca[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P2(1)2(1)2(1), and its molecular structure consists of a methacrylic ester of a ten-membered ring sesquiterpenoid annelated with an epoxide and a butyrolactone. The structure is stabilized by one intramolecular C-H center dot center dot center dot O hydrogen bond. An O-H center dot center dot center dot O hydrogen bond and further C-H center dot center dot center dot O interactions can be observed in the packing.}, language = {en} } @phdthesis{Mertens2017, author = {Mertens, Monique}, title = {Anwendungsorientierte Entwicklung neuer DBD-Derivate}, school = {Universit{\"a}t Potsdam}, pages = {222}, year = {2017}, language = {de} } @misc{KoenigKellingSchildeetal.2017, author = {K{\"o}nig, Jana and Kelling, Alexandra and Schilde, Uwe and Strauch, Peter}, title = {[µ2-O,O′,Oʺ,Oʺ′-Bis(1,2-dithiooxalato-S,S′)nickel(II)]bis[-O,O′-bis(1,2-dithiooxalato-S,S′)-nickel(II)pentaquaholmium(III)]hydrate, [Ho2Ni3(dto)6(H2O)10]}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400598}, pages = {5}, year = {2017}, abstract = {Planar bis(1,2-dithiooxalato)nickelate(II), [Ni(dto)]2- reacts in aqueous solutions with lanthanide ions (Ln3+) to form pentanuclear, hetero-bimetallic complexes of the general composition [{Ln(H2O)n}2{Ni(dto)2}3]·xH2O. (n = 4 or 5; x = 9-12). The complex [{Ho(H2O)5}2{Ni(dto)2}3]·10H2O, Ho2Ni3, was synthesized and characterized by single crystal X-ray structure analysis and powder diffraction. The Ho2Ni3 complex crystallizes as monoclinic crystals in the space group P21/c. The channels and cavities, appearing in the crystal packing of the complex molecules, are occupied by a varying amount of non-coordinated water molecules.}, language = {en} } @phdthesis{Witt2017, author = {Witt, Barbara}, title = {Toxicological characterization of lipid-soluble arsenic species in human brain cells}, school = {Universit{\"a}t Potsdam}, pages = {118, V}, year = {2017}, language = {en} } @misc{AdamovichMirskovaMirskovetal.2017, author = {Adamovich, Sergey N. and Mirskova, Anna N. and Mirskov, Rudolf G. and Schilde, Uwe}, title = {Synthesis and crystal structure of 1,4,10,13-tetraoxa-7,16-diazoniumcyclo-octadecane bis(4-chloro-2-methyl-phenoxyacetate)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400905}, pages = {4}, year = {2017}, abstract = {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.}, language = {en} } @phdthesis{Eckel2017, author = {Eckel, Nathalie}, title = {Metabolically healthy obesity and metabolically unhealthy normal weight - identification and associated risks}, school = {Universit{\"a}t Potsdam}, pages = {177}, year = {2017}, language = {en} } @misc{SullivanNitschkeSteupetal.2017, author = {Sullivan, Mitchell A. and Nitschke, Silvia and Steup, Martin and Minassian, Berge A. and Nitschke, Felix}, title = {Pathogenesis of Lafora disease}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1080}, issn = {1866-8372}, doi = {10.25932/publishup-47462}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-474622}, pages = {18}, year = {2017}, abstract = {Lafora disease (LD, OMIM \#254780) is a rare, recessively inherited neurodegenerative disease with adolescent onset, resulting in progressive myoclonus epilepsy which is fatal usually within ten years of symptom onset. The disease is caused by loss-of-function mutations in either of the two genes EPM2A (laforin) or EPM2B (malin). It characteristically involves the accumulation of insoluble glycogen-derived particles, named Lafora bodies (LBs), which are considered neurotoxic and causative of the disease. The pathogenesis of LD is therefore centred on the question of how insoluble LBs emerge from soluble glycogen. Recent data clearly show that an abnormal glycogen chain length distribution, but neither hyperphosphorylation nor impairment of general autophagy, strictly correlates with glycogen accumulation and the presence of LBs. This review summarizes results obtained with patients, mouse models, and cell lines and consolidates apparent paradoxes in the LD literature. Based on the growing body of evidence, it proposes that LD is predominantly caused by an impairment in chain-length regulation affecting only a small proportion of the cellular glycogen. A better grasp of LD pathogenesis will further develop our understanding of glycogen metabolism and structure. It will also facilitate the development of clinical interventions that appropriately target the underlying cause of LD.}, language = {en} } @phdthesis{Marschall2017, author = {Marschall, Talke Anu}, title = {Zytotoxizit{\"a}t, Bioverf{\"u}gbarkeit und Metabolismus kleiner Selenspezies in humanen Zellen und Entwicklung von ICP-QQQ-MS-basierten Methoden f{\"u}r deren Nachweis}, school = {Universit{\"a}t Potsdam}, pages = {115, VI}, year = {2017}, language = {de} } @phdthesis{Schmidt2017, author = {Schmidt, Martin}, title = {Entwicklung eines Verfahrens zur Herstellung von Florfliegenseide}, school = {Universit{\"a}t Potsdam}, pages = {135}, year = {2017}, language = {de} } @article{HermannsSchmidt2017, author = {Hermanns, Jolanda and Schmidt, Bernd}, title = {Zur Verwendung von QR-Codes in Uni-Seminaren - ein Baustein in den neu konzipierten {\"U}bungen zur Vorlesung „Organische Chemie f{\"u}r Studierende im Nebenfach"}, series = {Chemkon}, volume = {24}, journal = {Chemkon}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0944-5846}, doi = {10.1002/ckon.201710300}, pages = {139 -- 141}, year = {2017}, abstract = {Die Verwendung von QR-Codes in Begleitseminaren zur Vorlesung „Organische Chemie" f{\"u}r Studierende mit Chemie im Nebenfach wird vorgestellt. Die Hausaufgaben zu den Seminaren wurden mit einem QR-Code versehen. Dieser f{\"u}hrt zu weiterf{\"u}hrenden Hilfen. Der Einsatz der QR-Codes sowie die Neukonzeption der Seminare wurden evaluiert.}, language = {de} } @article{SchmidtAudoersch2017, author = {Schmidt, Bernd and Aud{\"o}rsch, Stephan}, title = {Stereoselective Total Syntheses of Polyacetylene Plant Metabolites via Ester-Tethered Ring Closing Metathesis}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02987}, pages = {1743 -- 1760}, year = {2017}, abstract = {Total syntheses of five naturally occurring polyacetylenes from three different plants are described. These natural products have in common an E,Z-configured conjugated diene linked to a di-or triyne chain. As the key method to stereoselectively establish the E,Z-diene part, an ester-tethered ring-closing metathesis/base-induced eliminative ring opening sequence was used. The results presented herein do not only showcase the utility of this tethered RCM variant but have also prompted us to suggest that the originally assigned absolute configurations of chiral polyacetylenes from Atractylodes macrocephala should be revised or at least reconsidered.}, language = {en} } @article{SchmidtRiemer2017, author = {Schmidt, Bernd and Riemer, Martin}, title = {Microwave-Promoted Pd-Catalyzed Synthesis of Dibenzofurans from Ortho-Arylphenols}, series = {Journal of Heterocyclic Chemistry}, volume = {54}, journal = {Journal of Heterocyclic Chemistry}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0022-152X}, doi = {10.1002/jhet.2704}, pages = {1287 -- 1297}, year = {2017}, abstract = {ortho-Aryl phenols, synthesized via protecting group free Suzuki-Miyaura coupling of ortho-halophenols and arene boronic acids, undergo a cyclization to dibenzofurans via oxidative C-H activation. The reaction proceeds under microwave irradiation in short reaction times using catalytic amounts of Pd(OAc)(2) without additional ligands.}, language = {en} } @phdthesis{Willersinn2017, author = {Willersinn, Jochen}, title = {Self-Assembly of double hydrophilic block copolymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-408578}, school = {Universit{\"a}t Potsdam}, pages = {119, clxxiv}, year = {2017}, abstract = {The motivation of this work was to investigate the self-assembly of a block copolymer species that attended little attraction before, double hydrophilic block copolymers (DHBCs). DHBCs consist of two linear hydrophilic polymer blocks. The self-assembly of DHBCs towards suprastructures such as particles and vesicles is determined via a strong difference in hydrophilicity between the corresponding blocks leading to a microphase separation due to immiscibility. The benefits of DHBCs and the corresponding particles and vesicles, such as biocompatibility, high permeability towards water and hydrophilic compounds as well as the large amount of possible functionalizations that can be addressed to the block copolymers make the application of DHBC based structures a viable choice in biomedicine. In order to assess a route towards self-assembled structures from DHBCs that display the potential to act as cargos for future applications, several block copolymers containing two hydrophilic polymer blocks were synthesized. Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone) (PEO-b-PVP) and Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone-co-N-vinylimidazole) (PEO-b-P(VP-co-VIm) block copolymers were synthesized via reversible deactivation radical polymerization (RDRP) techniques starting from a PEO-macro chain transfer agent. The block copolymers displayed a concentration dependent self-assembly behavior in water which was determined via dynamic light scattering (DLS). It was possible to observe spherical particles via laser scanning confocal microscopy (LSCM) and cryogenic scanning electron microscopy (cryo SEM) at highly concentrated solutions of PEO-b-PVP. Furthermore, a crosslinking strategy with (PEO-b-P(VP-co-VIm) was developed applying a diiodo derived crosslinker diethylene glycol bis(2-iodoethyl) ether to form quaternary amines at the VIm units. The formed crosslinked structures proved stability upon dilution and transfer into organic solvents. Moreover, self-assembly and crosslinking in DMF proved to be more advantageous and the crosslinked structures could be successfully transferred to aqueous solution. The afforded spherical submicron particles could be visualized via LSCM, cryo SEM and Cryo TEM. Double hydrophilic pullulan-b-poly(acrylamide) block copolymers were synthesized via copper catalyzed alkyne azide cycloaddition (CuAAC) starting from suitable pullulan alkyne and azide functionalized poly(N,N-dimethylacrylamide) (PDMA) and poly(N-ethylacrylamide) (PEA) homopolymers. The conjugation reaction was confirmed via SEC and 1H-NMR measurements. The self-assembly of the block copolymers was monitored with DLS and static light scattering (SLS) measurements indicating the presence of hollow spherical structures. Cryo SEM measurements could confirm the presence of vesicular structures for Pull-b-PEA block copolymers. Solutions of Pull-b-PDMA displayed particles in cryo SEM. Moreover, an end group functionalization of Pull-b-PDMA with Rhodamine B allowed assessing the structure via LSCM and hollow spherical structures were observed indicating the presence of vesicles, too. An exemplified pathway towards a DHBC based drug delivery vehicle was demonstrated with the block copolymer Pull-b-PVP. The block copolymer was synthesized via RAFT/MADIX techniques starting from a pullulan chain transfer agent. Pull-b-PVP displayed a concentration dependent self-assembly in water with an efficiency superior to the PEO-b-PVP system, which could be observed via DLS. Cryo SEM and LSCM microscopy displayed the presence of spherical structures. In order to apply a reversible crosslinking strategy on the synthesized block copolymer, the pullulan block was selectively oxidized to dialdehydes with NaIO4. The oxidation of the block copolymer was confirmed via SEC and 1H-NMR measurements. The self-assembled and oxidized structures were subsequently crosslinked with cystamine dihiydrochloride, a pH and redox responsive crosslinker resulting in crosslinked vesicles which were observed via cryo SEM. The vesicular structures of crosslinked Pull-b-PVP could be disassembled by acid treatment or the application of the redox agent tris(2-carboxyethyl)-phosphin-hydrochloride. The successful disassembly was monitored with DLS measurements. To conclude, self-assembled structures from DHBCs such as particles and vesicles display a strong potential to generate an impact on biomedicine and nanotechnologies. The variety of DHBC compositions and functionalities are very promising features for future applications.}, language = {en} } @phdthesis{Berthold2017, author = {Berthold, Thomas}, title = {Tannine f{\"u}r nachhaltige und funktionale Kohlenstoffmaterialien}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407564}, school = {Universit{\"a}t Potsdam}, pages = {85, xlvi}, year = {2017}, abstract = {In Zeiten eines sich schnell {\"a}ndernden und vielseitigen Energiemarktes m{\"u}ssen Kohlenstoffmaterialien f{\"u}r verschiedene Anforderungen einsetzbar sein. Dies erfordert flexibel synthetisierbare Kohlenstoffmaterialien bevorzugt aus g{\"u}nstigen und nachhaltigen Kohlenstoffquellen. Es ist allerdings nicht leicht Vorl{\"a}uferverbindungen auszumachen, welche sich einerseits f{\"u}r verschiedene Herstellungsverfahren eignen und deren Kohlenstoffprodukte andererseits in spezifischen Eigenschaften, wie der Struktur, des Stickstoffanteils, der Oberfl{\"a}che und der Porengr{\"o}ßen, eingestellt werden k{\"o}nnen. In diesem Zusammenhang k{\"o}nnen nat{\"u}rliche Polyphenole, etwa {\"u}bersch{\"u}ssige Tannine aus der Weinproduktion, eine neue Welt zu hoch funktionalen und vielseitig einstellbaren Kohlenstoffmaterialien mit hohen Ausbeuten {\"o}ffnen. Das Hauptziel dieser vorliegenden Thesis war es neue funktionale, einstellbare und skalierbare nanostrukturierte Kohlenstoffmaterialien aus Tanninen (insbesondere Tannins{\"a}ure) f{\"u}r unterschiedliche elektrochemische Zwecke zu synthetisieren und zu charakterisieren. Erm{\"o}glicht wurde dies durch unterschiedliche synthetische Herangehensweisen, wie etwa der polymeren Strukturdirektion, dem ionothermalen Templatieren und der weichen Templatierung. An Stelle des weitl{\"a}ufig gebr{\"a}uchlichen, aber kanzerogenen Vernetzungsagens Formaldehyd wurden bei den vorgestellten Synthesen Harnstoff und Thioharnstoff gew{\"a}hlt, um zugleich die synthetisierten Kohlenmaterialien variabel dotieren zu k{\"o}nnen. Daher wurden im ersten Teil der Arbeit die Wechselwirkungen, Reaktionen und thermischen Verhaltensweisen von Tannins{\"a}ure und Mixturen von Tannins{\"a}ure und Harnstoff bzw. Thioharnstoff untersucht, um daraus wichtige Erkenntnisse f{\"u}r die verschiedenen Kohlenstoffsynthesen zu gewinnen. Durch die Verwendung eines polymeren Strukturierungsagenz Pluronic P123 konnten in einer ersten Kohlenstoffsynthese nachhaltige und dotierbare Kohlenstoffpartikel mit Durchmessern im Nanometerbereich aus Tannins{\"a}ure und Harnstoff hergestellt werden. Es konnte dabei gezeigt werden, dass durch die Modifikation der verschiedenen Syntheseparameter die Kohlenstoffnanopartikel gem{\"a}ß ihres gemittelten Partikeldurchmessers, ihrer BET-Oberfl{\"a}che, ihrer Komposition, ihrer Leitf{\"a}higkeit und ihrer chemischen Stabilit{\"a}t einstellbar sind. Dies er{\"o}ffnete die M{\"o}glichkeit diese Kohlenstoffpartikel als alternatives und nachhaltiges Rußmaterial einzusetzen. Weiterhin war es durch die ionothermale Templatierung m{\"o}glich por{\"o}se, dotierte und kontrollierbare Kohlenstoffpartikel mit hohen spezifischen Oberfl{\"a}chen aus den gew{\"a}hlten Pr{\"a}kursorverbindungen zu synthetisieren, die sich f{\"u}r den Einsatz in Superkondensatoren eignen. Auf diesen Erkenntnissen aufbauend konnten mittels der Rotationsbeschichtung por{\"o}se binderfreie und strukturierte Kohlenstofffilme synthetisiert werden, die eine spinodale Struktur aufwiesen. Anhand der Modifikation der Stamml{\"o}sungskonzentration, der Rotationsgeschwindigkeit und der verwendeten Substrate konnten die Filmdicke (100-1000 nm), die Morphologie und Gesamtoberfl{\"a}che gezielt beeinflusst werden. Die erweiterte elektrochemische Analyse zeigte außerdem ein sehr gut zug{\"a}ngliches Porensystem der por{\"o}sen Kohlenstofffilme. Allumfassend konnten demnach verschiedene Synthesewege f{\"u}r Kohlenstoffmaterialien aus Tanninen aufgezeigt werden, die verschiedenartig strukturiert und kontrolliert werden k{\"o}nnen und sich f{\"u}r diverse Anwendungsgebiete eignen.}, language = {de} } @phdthesis{MbayaMani2017, author = {Mbaya Mani, Christian}, title = {Functional nanoporous carbon-based materials derived from oxocarbon-metal coordination complexes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407866}, school = {Universit{\"a}t Potsdam}, pages = {IV, 135}, year = {2017}, abstract = {Nanoporous carbon based materials are of particular interest for both science and industry due to their exceptional properties such as a large surface area, high pore volume, high electroconductivity as well as high chemical and thermal stability. Benefiting from these advantageous properties, nanoporous carbons proved to be useful in various energy and environment related applications including energy storage and conversion, catalysis, gas sorption and separation technologies. The synthesis of nanoporous carbons classically involves thermal carbonization of the carbon precursors (e.g. phenolic resins, polyacrylonitrile, poly(vinyl alcohol) etc.) followed by an activation step and/or it makes use of classical hard or soft templates to obtain well-defined porous structures. However, these synthesis strategies are complicated and costly; and make use of hazardous chemicals, hindering their application for large-scale production. Furthermore, control over the carbon materials properties is challenging owing to the relatively unpredictable processes at the high carbonization temperatures. In the present thesis, nanoporous carbon based materials are prepared by the direct heat treatment of crystalline precursor materials with pre-defined properties. This synthesis strategy does not require any additional carbon sources or classical hard- or soft templates. The highly stable and porous crystalline precursors are based on coordination compounds of the squarate and croconate ions with various divalent metal ions including Zn2+, Cu2+, Ni2+, and Co2+, respectively. Here, the structural properties of the crystals can be controlled by the choice of appropriate synthesis conditions such as the crystal aging temperature, the ligand/metal molar ratio, the metal ion, and the organic ligand system. In this context, the coordination of the squarate ions to Zn2+ yields porous 3D cube crystalline particles. The morphology of the cubes can be tuned from densely packed cubes with a smooth surface to cubes with intriguing micrometer-sized openings and voids which evolve on the centers of the low index faces as the crystal aging temperature is raised. By varying the molar ratio, the particle shape can be changed from truncated cubes to perfect cubes with right-angled edges. These crystalline precursors can be easily transformed into the respective carbon based materials by heat treatment at elevated temperatures in a nitrogen atmosphere followed by a facile washing step. The resulting carbons are obtained in good yields and possess a hierarchical pore structure with well-organized and interconnected micro-, meso- and macropores. Moreover, high surface areas and large pore volumes of up to 1957 m2 g-1 and 2.31 cm3 g-1 are achieved, respectively, whereby the macroscopic structure of the precursors is preserved throughout the whole synthesis procedure. Owing to these advantageous properties, the resulting carbon based materials represent promising supercapacitor electrode materials for energy storage applications. This is exemplarily demonstrated by employing the 3D hierarchical porous carbon cubes derived from squarate-zinc coordination compounds as electrode material showing a specific capacitance of 133 F g-1 in H2SO4 at a scan rate of 5 mV s-1 and retaining 67\% of this specific capacitance when the scan rate is increased to 200 mV s-1. In a further application, the porous carbon cubes derived from squarate-zinc coordination compounds are used as high surface area support material and decorated with nickel nanoparticles via an incipient wetness impregnation. The resulting composite material combines a high surface area, a hierarchical pore structure with high functionality and well-accessible pores. Moreover, owing to their regular micro-cube shape, they allow for a good packing of a fixed-bed flow reactor along with high column efficiency and a minimized pressure drop throughout the packed reactor. Therefore, the composite is employed as heterogeneous catalyst in the selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran showing good catalytic performance and overcoming the conventional problem of column blocking. Thinking about the rational design of 3D carbon geometries, the functions and properties of the resulting carbon-based materials can be further expanded by the rational introduction of heteroatoms (e.g. N, B, S, P, etc.) into the carbon structures in order to alter properties such as wettability, surface polarity as well as the electrochemical landscape. In this context, the use of crystalline materials based on oxocarbon-metal ion complexes can open a platform of highly functional materials for all processes that involve surface processes.}, language = {en} } @phdthesis{Meiling2017, author = {Meiling, Till Thomas}, title = {Development of a reliable and environmentally friendly synthesis for fluorescence carbon nanodots}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-410160}, school = {Universit{\"a}t Potsdam}, pages = {198}, year = {2017}, abstract = {Carbon nanodots (CNDs) have generated considerable attention due to their promising properties, e.g. high water solubility, chemical inertness, resistance to photobleaching, high biocompatibility and ease of functionalization. These properties render them ideal for a wide range of functions, e.g. electrochemical applications, waste water treatment, (photo)catalysis, bio-imaging and bio-technology, as well as chemical sensing, and optoelectronic devices like LEDs. In particular, the ability to prepare CNDs from a wide range of accessible organic materials makes them a potential alternative for conventional organic dyes and semiconductor quantum dots (QDs) in various applications. However, current synthesis methods are typically expensive and depend on complex and time-consuming processes or severe synthesis conditions and toxic chemicals. One way to reduce overall preparation costs is the use of biological waste as starting material. Hence, natural carbon sources such as pomelo peal, egg white and egg yolk, orange juice, and even eggshells, to name a few; have been used for the preparation of CNDs. While the use of waste is desirable, especially to avoid competition with essential food production, most starting-materials lack the essential purity and structural homogeneity to obtain homogeneous carbon dots. Furthermore, most synthesis approaches reported to date require extensive purification steps and have resulted in carbon dots with heterogeneous photoluminescent properties and indefinite composition. For this reason, among others, the relationship between CND structure (e.g. size, edge shape, functional groups and overall composition) and photophysical properties is yet not fully understood. This is particularly true for carbon dots displaying selective luminescence (one of their most intriguing properties), i.e. their PL emission wavelength can be tuned by varying the excitation wavelength. In this work, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain CNDs with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch, carboxylic acids and Tris-EDTA (TE) buffer as carbon- and nitrogen source, respectively. The presented microwave-assisted hydrothermal precursor carbonization (MW-hPC) is characterized by its cost-efficiency, simplicity, short reaction times, low environmental footprint, and high yields of approx. 80\% (w/w). Furthermore, only a single synthesis step is necessary to obtain homogeneous water-soluble CNDs with no need for further purification. Depending on starting materials and reaction conditions different types of CNDs have been prepared. The as-prepared CNDs exhibit reproducible, highly homogeneous and favourable PL properties with narrow emission bands (approx. 70nm FWHM), are non-blinking, and are ready to use without need for further purification, modification or surface passivation agents. Furthermore, the CNDs are comparatively small (approx. 2.0nm to 2.4nm) with narrow size distributions; are stable over a long period of time (at least one year), either in solution or as a dried solid; and maintain their PL properties when re-dispersed in solution. Depending on CND type, the PL quantum yield (PLQY) can be adjusted from as low as 1\% to as high as 90\%; one of the highest reported PLQY values (for CNDs) so far. An essential part of this work was the utilization of a microwave synthesis reactor, allowing various batch sizes and precise control over reaction temperature and -time, pressure, and heating- and cooling rate, while also being safe to operate at elevated reaction conditions (e.g. 230 ±C and 30 bar). The hereby-achieved high sample throughput allowed, for the first time, the thorough investigation of a wide range of synthesis parameters, providing valuable insight into the CND formation. The influence of carbon- and nitrogen source, precursor concentration and -combination, reaction time and -temperature, batch size, and post-synthesis purification steps were carefully investigated regarding their influence on the optical properties of as-synthesized CNDs. In addition, the change in photophysical properties resulting from the conversion of CND solution into solid and back into the solution was investigated. Remarkably, upon freeze-drying the initial brown CND-solution turns into a non-fluorescent white/slightly yellow to brown solid which recovers PL in aqueous solution. Selected CND samples were also subject to EDX, FTIR, NMR, PL lifetime (TCSPC), particle size (TEM), TGA and XRD analysis. Besides structural characterization, the pH- and excitation dependent PL characteristics (i.e. selective luminescence) were examined; giving inside into the origin of photophysical properties and excitation dependent behaviour of CNDs. The obtained results support the notion that for CNDs the nature of the surface states determines the PL properties and that excitation dependent behaviour is caused by the "Giant Red-Edge Excitation Shift" (GREES).}, language = {en} } @phdthesis{Heck2017, author = {Heck, Christian}, title = {Gold and silver nanolenses self-assembled by DNA origami}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-409002}, school = {Universit{\"a}t Potsdam}, pages = {ix, 125}, year = {2017}, abstract = {Nanolenses are linear chains of differently-sized metal nanoparticles, which can theoretically provide extremely high field enhancements. The complex structure renders their synthesis challenging and has hampered closer analyses so far. Here, the technique of DNA origami was used to self-assemble DNA-coated 10 nm, 20 nm, and 60 nm gold or silver nanoparticles into gold or silver nanolenses. Three different geometrical arrangements of gold nanolenses were assembled, and for each of the three, sets of single gold nanolenses were investigated in detail by atomic force microscopy, scanning electron microscopy, dark-field scattering and Raman spectroscopy. The surface-enhanced Raman scattering (SERS) capabilities of the single nanolenses were assessed by labelling the 10 nm gold nanoparticle selectively with dye molecules. The experimental data was complemented by finite-difference time-domain simulations. For those gold nanolenses which showed the strongest field enhancement, SERS signals from the two different internal gaps were compared by selectively placing probe dyes on the 20 nm or 60 nm gold particles. The highest enhancement was found for the gap between the 20 nm and 10 nm nanoparticle, which is indicative of a cascaded field enhancement. The protein streptavidin was labelled with alkyne groups and served as a biological model analyte, bound between the 20 nm and 10 nm particle of silver nanolenses. Thereby, a SERS signal from a single streptavidin could be detected. Background peaks observed in SERS measurements on single silver nanolenses could be attributed to amorphous carbon. It was shown that the amorphous carbon is generated in situ.}, language = {en} }