@article{KasyanenkoUnksovBakulevetal.2018, author = {Kasyanenko, Nina and Unksov, Ivan and Bakulev, Vladimir and Santer, Svetlana}, title = {DNA interaction with head-to-tail associates of cationic surfactants prevents formation of compact particles}, series = {Molecules}, volume = {23}, journal = {Molecules}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules23071576}, pages = {14}, year = {2018}, abstract = {Cationic azobenzene-containing surfactants are capable of condensing DNA in solution with formation of nanosized particles that can be employed in gene delivery. The ratio of surfactant/DNA concentration and solution ionic strength determines the result of DNA-surfactant interaction: Complexes with a micelle-like surfactant associates on DNA, which induces DNA shrinkage, DNA precipitation or DNA condensation with the emergence of nanosized particles. UV and fluorescence spectroscopy, low gradient viscometry and flow birefringence methods were employed to investigate DNA-surfactant and surfactant-surfactant interaction at different NaCl concentrations, [NaCl]. It was observed that [NaCl] (or the Debye screening radius) determines the surfactant-surfactant interaction in solutions without DNA. Monomers, micelles and non-micellar associates of azobenzene-containing surfactants with head-to-tail orientation of molecules were distinguished due to the features of their absorption spectra. The novel data enabled us to conclude that exactly the type of associates (together with the concentration of components) determines the result of DNA-surfactant interaction. Predomination of head-to-tail associates at 0.01 M < [NaCl] < 0.5 M induces DNA aggregation and in some cases DNA precipitation. High NaCl concentration (higher than 0.8 M) prevents electrostatic attraction of surfactants to DNA phosphates for complex formation. DAPI dye luminescence in solutions with DNA-surfactant complexes shows that surfactant tails overlap the DNA minor groove. The addition of di- and trivalent metal ions before and after the surfactant binding to DNA indicate that the bound surfactant molecules are located on DNA in islets.}, language = {en} } @misc{Santer2018, author = {Santer, Svetlana}, title = {Light responsive soft nano-objects}, series = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, volume = {256}, journal = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, publisher = {American Chemical Society}, address = {Washington}, issn = {0065-7727}, pages = {1}, year = {2018}, language = {en} } @article{FarhanRudolphNoecheletal.2018, author = {Farhan, Muhammad and Rudolph, Tobias and N{\"o}chel, Ulrich and Kratz, Karl and Lendlein, Andreas}, title = {Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(epsilon-caprolactone) Networks and Enable Self-Healing}, series = {Polymers}, volume = {10}, journal = {Polymers}, number = {3}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, doi = {10.3390/polym10030255}, pages = {15}, year = {2018}, abstract = {Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(epsilon-caprolactone) thermosets (cPCLs) were prepared from linear starting material, whereby the amount of extractable polymer was varied. Fractions of 5-60 wt \% of non-crosslinked polymer chains, which freely interpenetrate the crosslinked network, were achieved leading to differences in the resulting phase of the bulk material. This can be described as "sponge-like" with open or closed compartments depending on the amount of interpenetrating polymer. The crosslinking density and the average network chain length remained in a similar range for all network structures, while the theoretical accessible volume for reptation of the free polymer content is affected. This feature could influence or introduce new functions into the material created by thermomechanical treatment. The effect of interpenetrating PCL in cPCLs on the reversible actuation was analyzed by cyclic, uniaxial tensile tests. Here, high reversible strains of up to Delta epsilon = 24\% showed the enhanced actuation performance of networks with a non-crosslinked PCL content of 30 wt \% resulting from the crystal formation in the phase of the non-crosslinked PCL and co-crystallization with network structures. Additional functionalities are reprogrammability and self-healing capabilities for networks with high contents of extractable polymer enabling reusability and providing durable actuator materials.}, language = {en} } @phdthesis{Strunk2018, author = {Strunk, David}, title = {Gewinnung phenolischer Komponenten aus dem Birkenstamm als Rohstoffquelle f{\"u}r die Synthese eines neuen substituierten Phenylmethacrylats und dessen Polymerisation}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-409228}, school = {Universit{\"a}t Potsdam}, pages = {VIII, 157}, year = {2018}, abstract = {In der vorliegenden Arbeit werden Wege zur Gewinnung verschiedener phenolischer Substanzen wie Lignin, Diarylheptanoide und 4-(3-Oxobutyl)phenol (Himbeerketon) aus dem Stamm der H{\"a}ngebirke (Betula pendula) aufgezeigt. Durch Methacrylierung des 4-(3-Oxobutyl)phenols wurde ein Monomer erzeugt, welches mittels freier radikalischer Masse- und L{\"o}sungspolymerisation, sowie enzymatischer Polymerisation polymerisiert werden kann. Eine erste Isolierung von Bestandteilen wurde durch Extraktion von Innenholz bzw. Rinde mit Methanol erzielt. Die in Methanol unl{\"o}slichen Bestandteile des Innenholzes und der Rinde wurden anschließend mit ausgew{\"a}hlten ionischen Fl{\"u}ssigkeiten extrahiert. Es wurde ein Verfahren zum selektiven Trennen der mit diesen ionischen Fl{\"u}ssigkeiten extrahierten Bestandteile in Cellulose, Hemicellulose, Lignin und mit Ethylacetat extrahierbare Bestandteile entwickelt. Hierdurch war es m{\"o}glich, sowohl die verwendeten ionischen Fl{\"u}ssigkeiten als auch das Innenholz und die Rinde hinsichtlich ihres Extraktionsverhaltens miteinander zu vergleichen. Ferner wurden verschiedene Strategien aufgezeigt, um insgesamt drei Spezies an Diarylheptanoiden aus dem methanolischen Extrakt der Rinde zu isolieren. Eines der gefundenen Diarylheptanoide (5 Hydroxy-1,7-bis(4-hydroxyphenyl)-3-heptanon) wurde via Retroaldolreaktion in 4 (3 Oxobutyl)phenol (Himbeerketon) und 3 (4 Hydroxyphenyl)propanal gespalten. Es wurde die Verwendung des 4-(3-Oxobutyl)phenol als Monomerbestandteil untersucht. Hierf{\"u}r wurde 4-(3-Oxobutyl)phenylmethacrylat synthetisiert und Wege zur Reinigung mittels S{\"a}ulenchromatographie und Umkristallisation aufgezeigt. Anschließend wurde Poly(4-(3-oxobutyl)phenylmethacrylat) (PObMA) und Polybenzylmethacrylats (PBzMA) aus Massen- und L{\"o}sungspolymerisation hergestellt. Die Ausbeuten an PObpMA im Vergleich zum PBzMA liegen bei gleichen Reaktionsbedingungen auf gleichem Niveau. Im Kontrast hierzu ist der Polymerisationsgrad aus freier radikalischer Polymerisation in Masse des PObpMA im Vergleich zum PBzMA um den Faktor 3,7 gr{\"o}ßer. Die Glas{\"u}bergangstemperaturen des PObpMA liegen bei gleichen Reaktionsbedingungen sowohl bei freier radikalischer Polymerisation in Masse, als auch bei L{\"o}sungspolymerisation {\"u}ber denen des PBzMA. Dar{\"u}ber hinaus wurde die Polymerisation von 4-(3-Oxobutyl)phenylmethacrylat und Benzylmethacrylat mit einem Initiatorsystem bestehend aus Meerrettichperoxidase, Acetylaceton und Wasserstoffperoxid bei Raumtemperatur beschrieben. Die mit enzymatischem Initiatorsystem erzeugten Produkte zeigten starke {\"U}bereinstimmung mit Produkten aus L{\"o}sungspolymerisationen, welche mit Azobis(isobutyronitril) initiiert wurden.}, language = {de} } @phdthesis{Nizardo2018, author = {Nizardo, Noverra Mardhatillah}, title = {Thermoresponsive block copolymers with UCST-behavior aimed at biomedical environments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-412217}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 134}, year = {2018}, abstract = {Thermoresponsive block copolymers of presumably highly biocompatible character exhibiting upper critical solution temperature (UCST) type phase behavior were developed. In particular, these polymers were designed to exhibit UCST-type cloud points (Tcp) in physiological saline solution (9 g/L) within the physiologically interesting window of 30-50°C. Further, their use as carrier for controlled release purposes was explored. Polyzwitterion-based block copolymers were synthesized by atom transfer radical polymerization (ATRP) via a macroinitiator approach with varied molar masses and co-monomer contents. These block copolymers can self-assemble in the amphiphilic state to form micelles, when the thermoresponsive block experiences a coil-to-globule transition upon cooling. Poly(ethylene glycol) methyl ether (mPEG) was used as the permanently hydrophilic block to stabilize the colloids formed, and polyzwitterions as the thermoresponsive block to promote the temperature-triggered assembly-disassembly of the micellear aggregates at low temperature. Three zwitterionic monomers were used for this studies, namely 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate (SPE), 4-((2-(methacryloyl- oxy)ethyl)dimethylammonio)butane-1-sulfonate (SBE), and 3-((2-(methacryloyloxy)ethyl)- dimethylammonio)propane-1-sulfate) (ZPE). Their (co)polymers were characterized with respect to their molecular structure by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). Their phase behaviors in pure water as well as in physiological saline were studied by turbidimetry and dynamic light scattering (DLS). These (co)polymers are thermoresponsive with UCST-type phase behavior in aqueous solution. Their phase transition temperatures depend strongly on the molar masses and the incorporation of co-monomers: phase transition temperatures increased with increasing molar masses and content of poorly water-soluble co-monomer. In addition, the presence of salt influenced the phase transition dramatically. The phase transition temperature decreased with increasing salt content in the solution. While the PSPE homopolymers show a phase transition only in pure water, the PZPE homopolymers are able to exhibit a phase transition only in high salinity, as in physiological saline. Although both polyzwitterions have similar chemical structures that differ only in the anionic group (sulfonate group in SPE and sulfate group in ZPE), the water solubility is very different. Therefore, the phase transition temperatures of targeted block copolymers were modulated by using statistical copolymer of SPE and ZPE as thermoresponsive block, and varying the ratio of SPE to ZPE. Indeed, the statistical copolymers of P(SPE-co-ZPE) show phase transitions both in pure water as well as in physiological saline. Surprisingly, it was found that mPEG-b-PSBE block copolymer can display "schizophrenic" behavior in pure water, with the UCST-type cloud point occurring at lower temperature than the LCST-type one. The block copolymer, which satisfied best the boundary conditions, is block copolymer mPEG114-b-P(SPE43-co-ZPE39) with a cloud point of 45°C in physiological saline. Therefore, it was chosen for solubilization studies of several solvatochromic dyes as models of active agents, using the thermoresponsive block copolymer as "smart" carrier. The uptake and release of the dyes were explored by UV-Vis and fluorescence spectroscopy, following the shift of the wavelength of the absorbance or emission maxima at low and high temperature. These are representative for the loaded and released state, respectively. However, no UCST-transition triggered uptake and release of these dyes could be observed. Possibly, the poor affinity of the polybetaines to the dyes in aqueous environtments may be related to the widely reported antifouling properties of zwitterionic polymers.}, language = {en} } @article{LuReichetzederPrehnetal.2018, author = {Lu, Yong-Ping and Reichetzeder, Christoph and Prehn, Cornelia and Yin, Liang-Hong and Yun, Chen and Zeng, Shufei and Chu, Chang and Adamski, Jerzy and Hocher, Berthold}, title = {Cord blood Lysophosphatidylcholine 16:1 is positively associated with birth weight}, series = {Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry and pharmacology}, volume = {45}, journal = {Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry and pharmacology}, number = {2}, publisher = {Karger}, address = {Basel}, issn = {1015-8987}, doi = {10.1159/000487118}, pages = {614 -- 624}, year = {2018}, abstract = {Background/Aims: Impaired birth outcomes, like low birth weight, have consistently been associated with increased disease susceptibility to hypertension in later life. Alterations in the maternal or fetal metabolism might impact on fetal growth and influence birth outcomes. Discerning associations between the maternal and fetal metabolome and surrogate parameters of fetal growth could give new insight into the complex relationship between intrauterine conditions, birth outcomes, and later life disease susceptibility. Methods: Using flow injection tandem mass spectrometry, targeted metabolomics was performed in serum samples obtained from 226 mother/child pairs at delivery. Associations between neonatal birth weight and concentrations of 163 maternal and fetal metabolites were analyzed. Results: After FDR adjustment using the Benjamini-Hochberg procedure lysophosphatidylcholines (LPC) 14:0, 16:1, and 18:1 were strongly positively correlated with birth weight. In a stepwise linear regression model corrected for established confounding factors of birth weight, LPC 16: 1 showed the strongest independent association with birth weight (CI: 93.63 - 168.94; P = 6.94x10(-11)). The association with birth weight was stronger than classical confounding factors such as offspring sex (CI: - 258.81- -61.32; P = 0.002) and maternal smoking during pregnancy (CI: -298.74 - -29.51; P = 0.017). Conclusions: After correction for multiple testing and adjustment for potential confounders, LPC 16:1 showed a very strong and independent association with birth weight. The underlying molecular mechanisms linking fetal LPCs with birth weight need to be addressed in future studies. (c) 2018 The Author(s) Published by S. Karger AG, Basel}, language = {en} } @article{MuivaMutisyaAtilawHeydenreichetal.2018, author = {Muiva-Mutisya, Lois M. and Atilaw, Yoseph and Heydenreich, Matthias and Koch, Andreas and Akala, Hoseah M. and Cheruiyot, Agnes C. and Brown, Matthew L. and Irungu, Beatrice and Okalebo, Faith A. and Derese, Solomon and Mutai, Charles and Yenesew, Abiy}, title = {Antiplasmodial prenylated flavanonols from Tephrosia subtriflora}, series = {Natural Product Research}, volume = {32}, journal = {Natural Product Research}, number = {12}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1478-6419}, doi = {10.1080/14786419.2017.1353510}, pages = {1407 -- 1414}, year = {2018}, abstract = {The CH2Cl2/MeOH (1:1) extract of the aerial parts of Tephrosia subtriflora afforded a new flavanonol, named subtriflavanonol (1), along with the known flavanone spinoflavanone B, and the known flavanonols MS-II (2) and mundulinol. The structures were elucidated by the use of NMR spectroscopy and mass spectrometry. The absolute configuration of the flavanonols was determined based on quantum chemical ECD calculations. In the antiplasmodial assay, compound 2 showed the highest activity against chloroquine-sensitive Plasmodiumfalciparum reference clones (D6 and 3D7), artemisinin-sensitive isolate (F32-TEM) as well as field isolate (KSM 009) with IC50 values 1.4-4.6M without significant cytotoxicity against Vero and HEp2 cell lines (IC50>100M). The new compound (1) showed weak antiplasmodial activity, IC50 12.5-24.2M, but also showed selective anticancer activity against HEp2 cell line (CC50 16.9M). [GRAPHICS] .}, language = {en} } @article{TanLiuGlebeetal.2018, author = {Tan, Li and Liu, Bing and Glebe, Ulrich and B{\"o}ker, Alexander}, title = {Magnetic Field-Induced Assembly of Superparamagnetic Cobalt Nanoparticles on Substrates and at Liquid-Air Interface}, series = {Langmuir}, volume = {34}, journal = {Langmuir}, number = {46}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.8b02673}, pages = {13993 -- 14002}, year = {2018}, abstract = {Superparamagnetic cobalt nanoparticles (Co NPs) are an interesting material for self-assembly processes because of their magnetic properties. We investigated the magnetic field-induced assembly of superparamagnetic cobalt nanoparticles and compared three different approaches, namely, the assembly on solid substrates, at water-air, and ethylene glycol-air interfaces. Oleic acid- and trioctylphosphine oxide-coated Co NPs were synthesized via a thermolysis of cobalt carbonyl and dispersed into either hexane or toluene. The Co NP dispersion was dropped onto different substrates (e.g., transmission electron microscopy (TEM) grid, silicon wafer) and onto liquid surfaces. Transmission electron microscopy (TEM), scanning force microscopy, optical microscopy, as well as scanning electron microscopy showed that superparamagnetic Co NPs assembled into one-dimensional chains in an external magnetic field. By varying the concentration of the Co NP dispersion (1-5 mg/mL) and the strength of the magnetic field (4-54 mT), the morphology of the chains changed. Short, thin, and flexible chain structures were obtained at low NP concentration and low strength of magnetic field, whereas they became long, thick and straight when the NP concentration and the magnetic field strength increased. In comparison, the assembly of Co NPs from hexane dispersion at ethylene glycol-air interface showed the most regular and homogeneous alignment, since a more efficient spreading could be achieved on ethylene glycol than on water and solid substrates.}, language = {en} } @article{SunGlebeCharanetal.2018, author = {Sun, Zhiyong and Glebe, Ulrich and Charan, Himanshu and B{\"o}ker, Alexander and Wu, Changzhu}, title = {Enzyme-Polymer Conjugates as Robust Pickering Interfacial Biocatalysts for Efficient Biotransformations and One-Pot Cascade Reactions}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {57}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {42}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201806049}, pages = {13810 -- 13814}, year = {2018}, abstract = {Despite the rapid development of Pickering interfacial catalysis (PIC) at liquid-liquid interfaces with chemocatalysts, the use of unstable biocatalysts at emulsion interfaces remains a technical challenge. Herein, we present a Pickering interfacial biocatalysis (PIB) platform based on robust and recyclable enzyme-polymer conjugates that act as both catalytic sites and stabilizers at the interface of Pickering emulsions. The conjugates were prepared by growing poly(N-isopropylacrylamide) on a fragile enzyme, benzaldehyde lyase, under physiological conditions. The mild in situ conjugation process preserved the enzyme structure, and the conjugates were used to emulsify a water-organic two-phase system into a stable Pickering emulsion, leading to a significantly larger interfacial area and a 270-fold improvement in catalytic performance as compared to the unemulsified two-phase system. The PIB system could be reused multiple times. Conjugates of other enzymes were also fabricated and applied for cascade reactions.}, language = {en} } @phdthesis{Heinke2018, author = {Heinke, David}, title = {Biokompatible superparamagnetische Nanopartikel}, publisher = {Infinite Science Publishing}, address = {L{\"u}beck}, isbn = {978-3-945954-45-4}, pages = {142}, year = {2018}, abstract = {Magnetische Eisenoxidnanopartikel werden bereits seit geraumer Zeit erfolgreich als MRT-Kontrastmittel in der klinischen Bildgebung eingesetzt. Durch Optimierung der magnetischen Eigenschaften der Nanopartikel kann die Aussagekraft von MR-Aufnahmen verbessert und somit der diagnostische Wert einer MR-Anwendung weiter erh{\"o}ht werden. Neben der Verbesserung bestehender Verfahren wird die bildgebende Diagnostik ebenso durch die Entwicklung neuer Verfahren, wie dem Magnetic Particle Imaging, vorangetrieben. Da hierbei das Messsignal von den magnetischen Nanopartikeln selbst erzeugt wird, birgt das MPI einen enormen Vorteil hinsichtlich der Sensitivit{\"a}t bei gleichzeitig hoher zeitlicher und r{\"a}umlicher Aufl{\"o}sung. Da es aktuell jedoch keinen kommerziell vertriebenen in vivo-tauglichen MPI-Tracer gibt, besteht ein dringender Bedarf an geeigneten innovativen Tracermaterialien. Daraus resultierte die Motivation dieser Arbeit biokompatible und superparamagnetische Eisenoxidnanopartikel f{\"u}r den Einsatz als in vivo-Diagnostikum insbesondere im Magnetic Particle Imaging zu entwickeln. Auch wenn der Fokus auf der Tracerentwicklung f{\"u}r das MPI lag, wurde ebenso die MR-Performance bewertet, da geeignete Partikel somit alternativ oder zus{\"a}tzlich als MR-Kontrastmittel mit verbesserten Kontrasteigenschaften eingesetzt werden k{\"o}nnten. Die Synthese der Eisenoxidnanopartikel erfolgte {\"u}ber die partielle Oxidation von gef{\"a}lltem Eisen(II)-hydroxid und Green Rust sowie eine diffusionskontrollierte Kopr{\"a}zipitation in einem Hydrogel. Mit der partiellen Oxidation von Eisen(II)-hydroxid und Green Rust konnten erfolgreich biokompatible und {\"u}ber lange Zeit stabile Eisenoxidnanopartikel synthetisiert werden. Zudem wurden geeignete Methoden zur Formulierung und Sterilisierung etabliert, wodurch zahlreiche Voraussetzungen f{\"u}r eine Anwendung als in vivo-Diagnostikum geschaffen wurden. Weiterhin ist auf Grundlage der MPS-Performance eine hervorragende Eignung dieser Partikel als MPI-Tracer zu erwarten, wodurch die Weiterentwicklung der MPI-Technologie maßgeblich vorangetrieben werden k{\"o}nnte. Die Bestimmung der NMR-Relaxivit{\"a}ten sowie ein initialer in vivo-Versuch zeigten zudem das große Potential der formulierten Nanopartikelsuspensionen als MRT-Kontrastmittel. Die Modifizierung der Partikeloberfl{\"a}che erm{\"o}glicht ferner die Herstellung zielgerichteter Nanopartikel sowie die Markierung von Zellen, wodurch das m{\"o}gliche Anwendungsspektrum maßgeblich erweitert wurde. Im zweiten Teil wurden Partikel durch eine diffusionskontrollierte Kopr{\"a}zipitation im Hydrogel, wobei es sich um eine bioinspirierte Modifikation der klassischen Kopr{\"a}zipitation handelt, synthetisiert, wodurch Partikel mit einer durchschnittlichen Kristallitgr{\"o}ße von 24 nm generiert werden konnten. Die Bestimmung der MPS- und MR-Performance elektrostatisch stabilisierter Partikel ergab vielversprechende Resultate. In Vorbereitung auf die Entwicklung eines in vivo-Diagnostikums wurden die Partikel anschließend erfolgreich sterisch stabilisiert, wodurch der kolloidale Zustand in MilliQ-Wasser {\"u}ber lange Zeit aufrechterhalten werden konnte. Durch Zentrifugation konnten die Partikel zudem erfolgreich in verschiedene Gr{\"o}ßenfraktionen aufgetrennt werden. Dies erm{\"o}glichte die Bestimmung der idealen Aggregatgr{\"o}ße dieses Partikelsystems in Bezug auf die MPS-Performance.}, language = {de} } @article{AravopoulouKyriakosMiasnikovaetal.2018, author = {Aravopoulou, Dionysia and Kyriakos, Konstantinos and Miasnikova, Anna and Laschewsky, Andre and Papadakis, Christine M. and Kyritsis, Apostolos}, title = {Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {122}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {9}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.7b09647}, pages = {2655 -- 2668}, year = {2018}, abstract = {The thermoresponsive behavior of two diblock copolymers PS-b-PNIPAM and PS-b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt \% polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS-b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS-b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS-b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS-b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε′. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS-b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric "jump" experiments show that the kinetics of micellar aggregation in the PS-b-PMDEGA solution is slower than that in the PS-b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε′, is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition.}, language = {en} } @article{TadjoungWaffoYesildagCasertaetal.2018, author = {Tadjoung Waffo, Armel Franklin and Yesildag, Cigdem and Caserta, Giorgio and Katz, Sagie and Zebger, Ingo and Lensen, Marga C. and Wollenberger, Ulla and Scheller, Frieder W. and Altintas, Zeynep}, title = {Fully electrochemical MIP sensor for artemisinin}, series = {Sensors and actuators : B, Chemical}, volume = {275}, journal = {Sensors and actuators : B, Chemical}, publisher = {Elsevier}, address = {Lausanne}, issn = {0925-4005}, doi = {10.1016/j.snb.2018.08.018}, pages = {163 -- 173}, year = {2018}, abstract = {This study aims to develop a rapid, sensitive and cost-effective biomimetic electrochemical sensor for artemisinin determination in plant extracts and for pharmacokinetic studies. A novel molecularly imprinted polymer (MIP)based electrochemical sensor was developed by electropolymerization of o-phenylenediamine (o-PD) in the presence of artemisinin on gold wire surface for sensitive detection of artemisinin. The experimental parameters, including selection of functional monomer, polymerization conditions, template extraction after polymerization, influence of pH and buffer were all optimized. Every step of imprinted film synthesis were evaluated by employing voltammetry techniques, surface-enhanced infrared absorption spectroscopy (SEIRAS) and atomic force microscopy (AFM). The specificity was further evaluated by investigating non-specific artemisinin binding on non-imprinted polymer (NIP) surfaces and an imprinting factor of 6.8 was achieved. The artemisinin imprinted polymers using o-PD as functional monomer have provided highly stable and effective binding cavities for artemisinin. Cross-reactivity studies with drug molecules showed that the MIPs are highly specific for artemisinin. The influence of matrix effect was further investigated both in artificial plant matrix and diluted human serum. The results revealed a high affinity of artemisinin-MIP with dissociation constant of 7.3 x 10(-9) M and with a detection limit of 0.01 mu M and 0.02 mu M in buffer and plant matrix, respectively.}, language = {en} } @article{HeidenWirthCampenetal.2018, author = {Heiden, Sophia and Wirth, Jonas and Campen, Richard Kramer and Saalfrank, Peter}, title = {Water molecular beam scattering at alpha-Al2O3(0001)}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {122}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {27}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.8b04179}, pages = {15494 -- 15504}, year = {2018}, abstract = {Recent molecular beam experiments have shown that water may adsorb molecularly or dissociatively on an α-Al2O3(0001) surface, with enhanced dissociation probability compared to "pinhole dosing", i.e., adsorption under thermal equilibrium conditions. However, precise information on the ongoing reactions and their relative probabilities is missing. In order to shed light on molecular beam scattering for this system, we perform ab initio molecular dynamics calculations to simulate water colliding with α-Al2O3(0001). We find that single water molecules hitting a cold, clean surface from the gas phase are either reflected, molecularly adsorbed, or dissociated (so-called 1-2 dissociation only). A certain minimum translational energy (above 0.1 eV) seems to be required to enforce dissociation, which may explain the higher dissociation probability in molecular beam experiments. When the surface is heated and/or when refined surface and beam models are applied (preadsorption with water or water fragments, clustering and internal preexcitation in the beam), additional channels open, among them physisorption, water clustering on the surface, and so-called 1-4 and 1-4′ dissociation.}, language = {en} } @article{HeidenYueKirschetal.2018, author = {Heiden, Sophia and Yue, Yanhua and Kirsch, Harald and Wirth, Jonas A. and Saalfrank, Peter and Campen, Richard Kramer}, title = {Water dissociative adsorption on α-Al2O3(112̅0) is controlled by surface site undercoordination, density, and topology}, series = {The journal of physical chemistry / publ. weekly by the American Chemical Society : C, Nanomaterials and interfaces}, volume = {122}, journal = {The journal of physical chemistry / publ. weekly by the American Chemical Society : C, Nanomaterials and interfaces}, number = {12}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b10410}, pages = {6573 -- 6584}, year = {2018}, abstract = {α-Al2O3 surfaces are common in a wide variety of applications and useful models of more complicated, environmentally abundant, alumino-silicate surfaces. While decades of work have clarified that all properties of these surfaces depend sensitively on the crystal face and the presence of even small amounts of water, quantitative insight into this dependence has proven challenging. Overcoming this challenge requires systematic study of the mechanism by which water interacts with various α-Al2O3 surfaces. Such insight is most easily gained for the interaction of small amounts of water with surfaces in ultra high vacuum. In this study, we continue our combined theoretical and experimental approach to this problem, previously applied to water interaction with the α-Al2O3 (0001) and (11̅02) surfaces, now to water interaction with the third most stable surface, that is, the (112̅0). Because we characterize all three surfaces using similar tools, it is straightforward to conclude that the (112̅0) is most reactive with water. The most important factor explaining its increased reactivity is that the high density of undercoordinated surface Al atoms on the (112̅0) surface allows the bidentate adsorption of OH fragments originating from dissociatively adsorbed water, while only monodentate adsorption is possible on the (0001) and (11̅02) surfaces: the reactivity of α-Al2O3 surfaces with water depends strongly, and nonlinearly, on the density of undercoordinated surface Al atoms.}, language = {en} } @article{HeinzeHanschenWiesnerReinholdetal.2018, author = {Heinze, Mandy and Hanschen, Franziska S. and Wiesner-Reinhold, Melanie and Baldermann, Susanne and Gr{\"a}fe, Jan and Schreiner, Monika and Neugart, Susanne}, title = {Effects of Developmental Stages and Reduced UVB and Low UV Conditions on Plant Secondary Metabolite Profiles in Pak Choi (Brassica rapa subsp chinensis)}, series = {Journal of agricultural and food chemistry : a publication of the American Chemical Society}, volume = {66}, journal = {Journal of agricultural and food chemistry : a publication of the American Chemical Society}, number = {7}, publisher = {American Chemical Society}, address = {Washington}, issn = {0021-8561}, doi = {10.1021/acs.jafc.7b03996}, pages = {1678 -- 1692}, year = {2018}, abstract = {Pak choi (Brassica rapa subsp. chinensis) is rich in secondary metabolites and contains numerous antioxidants, including flavonoids; hydroxycinnamic acids; carotenoids; chlorophylls; and glucosinolates, which can be hydrolyzed to epithionitriles, nitriles, or isothiocyanates. Here, we investigate the effect of reduced exposure to ultraviolet B (UVB) and UV (UVA and UVB) light at four different developmental stages of pak choi. We found that both the plant morphology and secondary metabolite profiles were affected by reduced exposure to UVB and UV, depending on the plant's developmental stage. In detail, mature 15- and 30-leaf plants had higher concentrations of flavonoids, hydroxycinnamic acids, carotenoids, and chlorophylls, whereas sprouts contained high concentrations of glucosinolates and their hydrolysis products. Dry weights and leaf areas increased as a result of reduced UVB and low UV. For the flavonoids and hydroxycinnamic acids in 30-leaf plants, less complex compounds were favored, for example, sinapic acid acylated kaempferol triglycoside instead of the corresponding tetraglycoside. Moreover, also in 30-leaf plants, zeaxanthin, a carotenoid linked to protection during photosynthesis, was increased under low UV conditions. Interestingly, most glucosinolates were not affected by reduced UVB and low UV conditions. However, this study underlines the importance of 4-(methylsulfinyl)butyl glucosinolate in response to UVA and UVB exposure. Further, reduced UVB and low UV conditions resulted in higher concentrations of glucosinolate-derived nitriles. In conclusion, exposure to low doses of UVB and UV from the early to late developmental stages did not result in overall lower concentrations of plant secondary metabolites.}, language = {en} } @article{HeckKanehiraKneippetal.2018, author = {Heck, Christian and Kanehira, Yuya and Kneipp, Janina and Bald, Ilko}, title = {Placement of Single Proteins within the SERS Hot Spots of Self-Assembled Silver Nanolenses}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {57}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {25}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201801748}, pages = {7444 -- 7447}, year = {2018}, abstract = {This study demonstrates the bottom-up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10nm, 20nm, and 60nm in diameter were self-assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface-enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self-similar aggregates of solid silver nanoparticles are promising for plasmonic applications.}, language = {en} } @article{FerrerPeresdosSantosetal.2018, author = {Ferrer, Beatriz and Peres, Tanara Vieira and dos Santos, Alessandra Antunes and Bornhorst, Julia and Morcillo, Patricia and Goncalves, Cinara Ludvig and Aschner, Michael}, title = {Methylmercury affects the expression of hypothalamic neuropeptides that control body weight in C57BL/6J mice}, series = {Toxicological sciences}, volume = {163}, journal = {Toxicological sciences}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {1096-6080}, doi = {10.1093/toxsci/kfy052}, pages = {557 -- 568}, year = {2018}, abstract = {Methylmercury (MeHg) is an environmental pollutant that affects primarily the central nervous system (CNS), causing neurological alterations. An early symptom of MeHg poisoning is the loss of body weight and appetite. Moreover, the CNS has an important role in controlling energy homeostasis. It is known that in the hypothalamus nutrient and hormonal signals converge to orchestrate control of body weight and food intake. In this study, we investigated if MeHg is able to induce changes in the expression of key hypothalamic neuropeptides that regulate energy homeostasis. Thus, hypothalamic neuronal mouse cell line GT 1-7 was treated with MeHg at different concentrations (0, 0.5, 1, and 5 mu M). MeHg induced the expression of the anorexigenic neuropeptide pro-omiomelanocortin (Pomc) and the orexigenic peptide Agouti-related peptide (Agrp) in a concentration-dependent manner, suggesting deregulation of mechanisms that control body weight. To confirm these in vitro observations, 8-week-old C57BL/6J mice (males and females) were exposed to MeHg in drinking water, modeling the most prevalent exposure route to this metal. After 30-day exposure, no changes in body weight were detected. However, MeHg treated males showed a significant decrease in fat depots. Moreover, MeHg affected the expression of hypothalamic neuropeptides that control food intake and body weight in a gender-and dose-dependent manner. Thus, MeHg increases Pomc mRNA only in males in a dose-dependent way, and it does not have effects on the expression of Agrp mRNA. The present study shows, for first time, that MeHg is able to induce changes in hypothalamic neuropeptides that regulate energy homeostasis, favoring an anorexigenic/catabolic profile.}, language = {en} } @article{VishnevetskayaHildebrandDyakonovaetal.2018, author = {Vishnevetskaya, Natalya S. and Hildebrand, Viet and Dyakonova, Margarita A. and Niebuur, Bart-Jan and Kyriakos, Konstantinos and Raftopoulos, Konstantinos N. and Di, Zhenyu and M{\"u}ller-Buschbaum, Peter and Laschewsky, Andre and Papadakis, Christine M.}, title = {Dual orthogonal switching of the "Schizophrenic" self-assembly of diblock copolymers}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {51}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {7}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/acs.macromol.8b00096}, pages = {2604 -- 2614}, year = {2018}, abstract = {Based on diblock copolymers, a pair of "schizophrenic" micellar systems is designed by combining a nonionic and thermoresponsive block with a zwitterionic block, which is thermoresponsive and salt-sensitive. The nonionic block is poly(N-isopropylacrylamide) (PNIPAM) or poly(N-isopropylmethacrylamide) (PNIPMAM) and exhibits a lower critical solution temperature (LCST) behavior in aqueous solution. The zwitterionic block is a polysulfobetaine, i.e., poly(4((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate) (PSBP), and has an upper critical solution temperature (UCST) behavior with the clearing point decreasing with increasing salt concentration. The PSBP-b-PNIPAM and PSBP-b-PNIPMAM diblock copolymers are prepared by successive reversible addition-fragmentation chain transfer (RAFT) polymerizations. The PSBP block is chosen such that the clearing point of the homopolymer is significantly higher in pure water than the cloud point of PNIPAM or PNIPMAM. Using turbidimetry, H-1 NMR, and small-angle neutron scattering, we investigate the overall phase behavior as well as the structure and interaction between the micelles and the intermediate phase, both in salt-free D2O and in 0.004 M NaBr in D2O in a wide temperature range. We find that PSBP-b-PNIPAM at 50 g L-1 in salt-free D2O is turbid in the entire temperature range. It forms spherical micelles below the cloud point of PNIPAM and cylindrical micelles above. Similar behavior is observed for PSBP-b-PNIPMAM at 50 g L-1 in salt-free D2O with a slight and smooth increase of the light transmission below the cloud point of PNIPMAM and an abrupt decrease above. Upon addition of 0.004 M NaBr, the UCST-type cloud point of the PSBP-block is notably decreased, and an intermediate regime is encountered below the cloud point of PNIPMAM, where the light transmission is slightly enhanced. In this regime, the polymer solution exhibits behavior typical for polyelectrolyte solutions. Thus, double thermosensitive and salt-sensitive behavior with "schizophrenic" micelle formation is found, and the width of the intermediate regime, where both blocks are hydrophilic, can be tuned by the addition of electrolyte.}, language = {en} } @article{ZhongMiMetwallietal.2018, author = {Zhong, Qi and Mi, Lei and Metwalli, Ezzeldin and Biessmann, Lorenz and Philipp, Martine and Miasnikova, Anna and Laschewsky, Andre and Papadakis, Christine M. and Cubitt, Robert and Schwartzkopf, Matthias and Roth, Stephan V. and Wang, Jiping and M{\"u}ller-Buschbaum, Peter}, title = {Effect of chain architecture on the swelling and thermal response of star-shaped thermo-responsive (poly(methoxy diethylene glycol acrylate)-block-polystyrene)(3) block copolymer films}, series = {Soft matter}, volume = {14}, journal = {Soft matter}, number = {31}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c8sm00965a}, pages = {6582 -- 6594}, year = {2018}, abstract = {The effect of chain architecture on the swelling and thermal response of thin films obtained from an amphiphilic three-arm star-shaped thermo-responsive block copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene ((PMDEGA-b-PS)(3)) is investigated by in situ neutron reflectivity (NR) measurements. The PMDEGA and PS blocks are micro-phase separated with randomly distributed PS nanodomains. The (PMDEGA-b-PS)(3) films show a transition temperature (TT) at 33 degrees C in white light interferometry. The swelling capability of the (PMDEGA-b-PS)(3) films in a D2O vapor atmosphere is better than that of films from linear PS-b-PMDEGA-b-PS triblock copolymers, which can be attributed to the hydrophilic end groups and limited size of the PS blocks in (PMDEGA-b-PS)(3). However, the swelling kinetics of the as-prepared (PMDEGA-b-PS)(3) films and the response of the swollen film to a temperature change above the TT are significantly slower than that in the PS-b-PMDEGA-b-PS films, which may be related to the conformation restriction by the star-shape. Unlike in the PS-b-PMDEGA-b-PS films, the amount of residual D2O in the collapsed (PMDEGA-b-PS)(3) films depends on the final temperature. It decreases from (9.7 +/- 0.3)\% to (7.0 +/- 0.3)\% or (6.0 +/- 0.3)\% when the final temperatures are set to 35 degrees C, 45 degrees C and 50 degrees C, respectively. This temperature-dependent reduction of embedded D2O originates from the hindrance of chain conformation from the star-shaped chain architecture.}, language = {en} } @article{NoackSchanzenbachKoetzetal.2018, author = {Noack, Sebastian and Schanzenbach, Dirk and Koetz, Joachim and Schlaad, Helmut}, title = {Polylactide-based amphiphilic block copolymers}, series = {Macromolecular rapid communications}, volume = {40}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201800639}, pages = {6}, year = {2018}, abstract = {The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures.}, language = {en} }