TY - JOUR A1 - Bapolisi, Alain Murhimalika A1 - Kielb, Patrycja A1 - Bekir, Marek A1 - Lehnen, Anne-Catherine A1 - Radon, Christin A1 - Laroque, Sophie A1 - Wendler, Petra A1 - Müller-Werkmeister, Henrike A1 - Hartlieb, Matthias T1 - Antimicrobial polymers of linear and bottlebrush architecture BT - Probing the membrane interaction and physicochemical properties JF - Macromolecular rapid communications : publishing the newsletters of the European Polymer Federation N2 - Polymeric antimicrobial peptide mimics are a promising alternative for the future management of the daunting problems associated with antimicrobial resistance. However, the development of successful antimicrobial polymers (APs) requires careful control of factors such as amphiphilic balance, molecular weight, dispersity, sequence, and architecture. While most of the earlier developed APs focus on random linear copolymers, the development of APs with advanced architectures proves to be more potent. It is recently developed multivalent bottlebrush APs with improved antibacterial and hemocompatibility profiles, outperforming their linear counterparts. Understanding the rationale behind the outstanding biological activity of these newly developed antimicrobials is vital to further improving their performance. This work investigates the physicochemical properties governing the differences in activity between linear and bottlebrush architectures using various spectroscopic and microscopic techniques. Linear copolymers are more solvated, thermo-responsive, and possess facial amphiphilicity resulting in random aggregations when interacting with liposomes mimicking Escheria coli membranes. The bottlebrush copolymers adopt a more stable secondary conformation in aqueous solution in comparison to linear copolymers, conferring rapid and more specific binding mechanism to membranes. The advantageous physicochemical properties of the bottlebrush topology seem to be a determinant factor in the activity of these promising APs. KW - antimicrobial polymers KW - bottlebrush copolymers KW - liposomes KW - membrane KW - interactions KW - quartz crystal microbalance Y1 - 2022 U6 - https://doi.org/10.1002/marc.202200288 SN - 1521-3927 SN - 1022-1336 VL - 43 IS - 19 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Jeon, Jae-Hyung A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion N2 - Anomalous diffusion is frequently described by scaled Brownian motion (SBM){,} a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is ?x2(t)? [similar{,} equals] 2K(t)t with K(t) [similar{,} equals] t[small alpha]-1 for 0 < [small alpha] < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion{,} for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely{,} we demonstrate that under confinement{,} the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments{,} in particular{,} under confinement inside cellular compartments or when optical tweezers tracking methods are used. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 180 KW - single-particle tracking KW - living cells KW - random-walks KW - subdiffusion KW - dynamics KW - nonergodicity KW - coefficients KW - transport KW - membrane KW - behavior Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76302 SP - 15811 EP - 15817 ER - TY - JOUR A1 - Jeon, Jae-Hyung A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion JF - Physical chemistry, chemical physics : PCCP N2 - Anomalous diffusion is frequently described by scaled Brownian motion (SBM){,} a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is ?x2(t)? [similar{,} equals] 2K(t)t with K(t) [similar{,} equals] t[small alpha]-1 for 0 < [small alpha] < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion{,} for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely{,} we demonstrate that under confinement{,} the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments{,} in particular{,} under confinement inside cellular compartments or when optical tweezers tracking methods are used. KW - single-particle tracking KW - living cells KW - random-walks KW - subdiffusion KW - dynamics KW - nonergodicity KW - coefficients KW - transport KW - membrane KW - behavior Y1 - 2014 U6 - https://doi.org/10.1039/C4CP02019G VL - 30 IS - 16 SP - 15811 EP - 15817 PB - The Royal Society of Chemistry CY - Cambridge ER - TY - BOOK A1 - Gutlederer, Erwin Johann T1 - On the morphology of vesicles. - [überarb. Diss.] N2 - This dissertation contains theoretical investigations on the morphology and statistical mechanics of vesicles. The shapes of homogeneous fluid vesicles and inhomogeneous vesicles with fluid and solid membrane domains are calculated. The influence of thermal fluctuations is investigated. The obtained results are valid on mesoscopic length scales and are based on a geometrical membrane model, where the vesicle membrane is described as either a static or a thermal fluctuating surface. The thesis consists of three parts. In the first part, homogeneous vesicles are considered. The focus in this part is on the thermally induced morphological transition between vesicles with prolate and oblate shape. With the help of Monte Carlo simulations, the free energy profile of these vesicles is determined. It can be shown that the shape transformation between prolate and oblate vesicles proceeds continuously and is not hampered by a free energy barrier. The second and third part deal with inhomogeneous vesicles which contain intramembrane domains. These investigations are motivated by experimental results on domain formation in single or multicomponent vesicles, where phase separation occurs and different membrane phases coexist. The resulting domains differ with regard to their membrane structure (solid, fluid). The membrane structure has a distinct effect on the form of the domain and the morphology of the vesicle. In the second part, vesicles with coexisting solid and fluid membrane domains are studied, while the third part addresses vesicles with coexisting fluid domains. The equilibrium morphology of vesicles with simple and complex domain forms, derived through minimisation of the membrane energy, is determined as a function of material parameters. The results are summarised in morphology diagrams. These diagrams show previously unknown morphological transitions between vesicles with different domain shapes. The impact of thermal fluctuations on the vesicle and the form of the domains is investigated by means of Monte Carlo simulations. N2 - Die vorliegende Arbeit enthält theoretische Untersuchungen zur Morphologie und statistischen Mechanik von Vesikeln. Es wird die Gestalt homogener fluider Vesikel und inhomogener Vesikel mit fluiden und festen Membrandomänen berechnet. Der Einfluss thermischer Fluktuationen wird untersucht. Die erzielten Ergebnisse beziehen sich auf mesoskopische Längenskalen und basieren auf einem geometrischen Membranmodell, in welchem die Vesikelmembran als statische, beziehungsweise thermisch fluktuierende Fläche beschrieben wird. Die Arbeit besteht aus drei Teilen. Im ersten Teil werden homogene fluide Vesikel betrachtet. Das Interesse gilt dem thermisch induzierten Morphologieübergang zwischen prolaten und oblaten Vesikelformen. Mit Hilfe von Monte-Carlo-Simulationen wird ein freies Energieprofil für diese Vesikel ermittelt. Es kann gezeigt werden, dass die Formumwandlung zwischen prolaten und oblaten Formen kontinuierlich verläuft und mit keiner freien Energiebarriere verbunden ist. Der zweite und dritte Teil beschäftigt sich mit inhomogenen Vesikeln, die intramembrane Domänen enthalten. Ausgangspunkt und Motivation der Berechnungen sind experimentelle Studien über Domänbildung in ein- oder mehrkomponentigen Vesikelmembranen, bei denen Phasentrennung stattfindet und unterschiedliche Membranphasen koexistieren. Die dabei auftretenden Domänen unterscheiden sich hinsichtlich ihrer Membranstruktur (fest, fluid). Diese beeinflusst die Form der Domäne und des gesamten Vesikels auf entscheidende Weise. Im zweiten Teil werden Vesikel untersucht, bei denen feste und fluide Membrandomänen koexistieren, Teil drei widmet sich Vesikeln mit zwei koexistierenden fluiden Membranphasen. In Abhängigkeit von Materialparametern werden durch Minimierung der Membranenergie die Grundzustandsformen von Vesikeln mit einfachen und komplexen Domänenformen bestimmt. Die Ergebnisse werden in Morphologiediagrammen zusammengefasst. Dabei werden bisher unbekannte Morphologieübergänge zwischen Vesikeln mit unterschiedlichen Domänformen beobachtet. Die Auswirkungen thermischer Fluktuationen auf die Vesikel und die Form ihrer Domänen werden mittels Monte-Carlo-Simulationen untersucht. KW - Vesikel KW - Membran KW - Domänen KW - vesicle KW - membrane KW - domains Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15065 ER -