Highlight Publications 2018

Specific Ion Effects on an Oligopeptide: Bidentate binding matters for the Guanidinium Cation
Vasileios Balos, Bogdan Marekha, Christian Malm, Manfred Wagner, Yuki Nagata, Mischa Bonn, Johannes Hunger
Specific Ion Effects on an Oligopeptide: Bidentate binding matters for the Guanidinium Cation
Ion‐protein interactions are important for protein function, yet challenging to rationalize due to the multitude of ion‐protein interaction possibilities. To explore specific ion effects on protein binding sites, we investigate the interaction of different salts with the zwitterionic peptide triglycine in solution. Dielectric spectroscopy experiments show that salts affect the peptide’s reorientational dynamics, with a more pronounced effect of denaturing cations (Li+, guanidinium Gdm+) and anions (I‐, SCN‐) than weakly denaturing ones (K+, Cl‐). Notably, we find the effect of Gdm+ and Li+ to be comparable. Molecular dynamics simulations confirm the enhanced binding of Gdm+ and Li+ to triglycine, yet with a different binding geometry: While Li+ predominantly binds to the C‐terminal carboxylate group, bidentate binding to the terminus and the nearest amide is particularly important for Gdm+. This bidentate binding markedly affects peptide conformation. As such, this bidentate binding geometry may help explain the high denaturation activity of Gdm+ salts.
© Vasileios Balos (2018)
How the guanidinium cation unfolds a protein
Light guided motility of a minimal synthetic cell
Solveig M. Bartelt, Jan Steinkühler, Rumiana Dimova and Seraphine V. Wegner
Light guided motility of a minimal synthetic cell
Cell motility is an important but complex process; as cells move new adhesions form at the front and adhesions disassemble at the back. To replicate this dynamic and spatiotemporally controlled asymmetry of adhesions and achieve motility in a minimal synthetic cell, we controlled the adhesion of a model giant unilamellar vesicle (GUV) to the substrate with light. For this purpose, we immobilized the proteins iLID and Micro, which interact under blue light and dissociate from each other in the dark, on a substrate and a GUV, respectively. Under blue light the protein interaction leads to adhesion of the vesicle to the substrate, which is reversible in the dark. The high spatiotemporal control provided by light, allowed partly illuminating the GUV and generating an asymmetry in adhesions. Consequently, the GUV moves into the illuminated area, a process that can be repeated over multiple cycles. Thus, our system reproduces the dynamic spatiotemporal distribution of adhesions and establishes mimetic motility of a synthetic cell.
© MPI-P (2018)
Light guided motility of a minimal synthetic cell.
Ultrathin Shell Layers Dramatically Influence Polymer Nanoparticle Surface Mobility
Eunsoo Kang, Hojin Kim, Laura A. G. Gray, Dane Christie, Ulrich Jonas, Bartlomiej Graczykowski, Eric M. Furst, Rodney D. Priestley , and George Fytas
Ultrathin Shell Layers Dramatically Influence Polymer Nanoparticle Surface Mobility
The vibration spectrum of individual polymer colloids (red) is a sensitive probe of their adhesion and in a colloidal cluster (blue) as schematically shown. Nanometer thick shells can drastically affect the particle surface mobility (softening temperature) of the glassy core and the elastic shear modulus (G). The particles can be either more flexible or rigid at the surface than the core. We added a shell atop the nanoparticle either by seeded surfactant-free emulsion polymerization or layer-by-layer method. Our group has recently introduced this direct probe of particle surface mobility via the polymer colloid vibrations recorded by BLS spectroscopy (Kim et al., Nat. Commun. 9, 2918,2018).
© Bartlomiej Graczykowski, Eunsoo Kang (2018)
MPIP researchers in collaboration with Prof. Priestley’s and Prof. Furst’s group, and Prof. Jonas investigated ultrathin shell layer effect on polymer nanoparticle surface mobility and elastic modulus by Brillouin Light Spectroscopy.
Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide
Tassilo Gleede, Elisabeth Rieger, Jan Blankenburg, Katja Klein, and Frederik R. Wurm
Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide
An ideal system for stimuli-responsive and amphiphilic (block) polymers would be the copolymerization of aziridines with epoxides. However, to date, no copolymerization of these two highly strained three-membered heterocycles had been achieved. We report the combination of living oxy- and azaanionic ring-opening polymerization of ethylene oxide (EO) and sulfonamide-activated aziridines. In a single step, well-defined amphiphilic block copolymers are obtained by a one-pot copolymerization. The highest difference of reactivity ratios ever reported for an anionic copolymerization (with r1=265 and r2=0.004 for 2-methyl-N-tosylaziridine/ EO) led to the formation of block copolymers in a closed system. The amphiphilic diblock copolymers were used a novel class of nonionic and responsive surfactants. In addition, this unique comonomer reactivity allowed fast access to multiblock copolymers: we prepared the first amphiphilic penta- or tetrablock copolymers containing aziridines in only one or two steps, respectively. These examples render the combination of epoxide and aziridine copolymerization to a powerful strategy to sophisticated macromolecular architectures and nanostructures.
© MPI-P (2018)
Block copolymers of aziridines and ethylene oxide are prepared in a closed-reactor without sequential monomer addition.
Plastics of the future? The impact of biodegradable polymers on the environment and on society
Tobias Haider, Carolin Völker, Johanna Kramm, Katharina Landfester, Frederik R. Wurm
Plastics of the future? The impact of biodegradable polymers on the environment and on society
We are living in a plastic age. For most of us, life without polymers and plastics is unthinkable. However, in recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in research and the news. Biodegradable polymers might be a suitable alternative to commodity plastics to minimize the impact of plastics on the environment. However, their degradation rates crucially depend on the environments they end up in, such as soil or marine water, or when used in biomedical devices. We show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.
© Wiley VCH (2018)
Biodegradable polymers. Currents materials and future perspectives are discussed.
Evidence for auto-catalytic mineral dissolution from surface-specific vibrational spectroscopy
Jan Schaefer, Ellen H. G. Backus & Mischa Bonn
Evidence for auto-catalytic mineral dissolution from surface-specific vibrational spectroscopy
In nature, many geologically relevant processes are driven by non-equilibrium interfacial effects: Water typically flows and doesn’t stand still. A key example is the dissolution of minerals, like silica, in water. By using time-dependent surface specific spectroscopy in the presence and absence of flow of water, we determine the dissolution kinetics of silica in a direct way. The interfacial insights of this approach reveal that the macroscopic dissolution process of silica is limited by diffusion. The molecular dissolution mechanism appears autocatalytic: the presence of dissolved silicate close to the interface speeds up the dissolution process.
© Nature (2018)
Interfacial spectroscopy reveals: Silica dissolution is self-accelerating and limited by diffusion.
Vibrational coupling between organic and inorganic sub‐lattices of hybrid perovskites
Maksim Grechko Simon A. Bretschneider Laura Vietze Heejae Kim Mischa Bonn
Vibrational coupling between organic and inorganic sub‐lattices of hybrid perovskites
The excellent photovoltaic performance of perovskite solar cells has inspired significant interest in the fundamental photophysical properties of this promising material. One of the most challenging fundamental issues is coupling between different motions of electrons and nuclei in the lattice of perovskite semiconductors. In the present work, we reveal direct coupling between phonon vibrations of inorganic sub-lattice and high-frequency molecular vibrations of organic sub-lattice of hybrid organic-inorganic perovskites. Mixing of the phonon and molecular vibrations can provide additional energy relaxation pathways for photoexcited electrons in the conduction band and, thus, elucidate the faster hot-carrier cooling rates in the MA/FAPbI3 as compared to the CsPbI3 perovskites.
© Wiley VCH (2018)
A newly developed spectroscopy reveals coupling between low-frequency phonon modes and high-frequency molecular vibrations in a hybrid organic – inorganic perovskite.
Red-Light-Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments
Wen Sun, Yan Wen, Raweewan Thiramanas, Mingjia Chen, Jianxiong Han, Ningqiang Gong, Manfred Wagner, Shuai Jiang, Michael S. Meijer, Sylvestre Bonnet, Hans-Jürgen Butt, Volker Mailänder, Xing-Jie Liang, and Si Wu
Red-Light-Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments
Amphiphilic metallopolymers, which contain photocleavable drug-Ru complex conjugates, self-assemble into micelles. The micelles are biocompatible and carry the conjugates into tumor cells. Subsequent red light irradiation induces intracellular release of the drug-Ru complex conjugates. Because the photoinduced release is oxygen-independent, the novel metallopolymer provides a new platform for phototherapy against hypoxic tumors in vivo.
© Wiley (2018)
 
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