Doctoral students seminar (January 16, 2018)

Geometrical stiffness studied by a coarse grained homopolymer model

by Benno Werlich

Morphologies of biopolymers depend on the interaction energies and on stiffness. We use a coarse grained homopolymer model to study geometrical stiffness as bond length variation. Therefore we show a wide range of stable structures which are known from different stiffness approaches and also from experiments. With the help of canonical and microcanonical analysis we created a state diagram for a broad range of stiffness from flexible to very stiff chains. Simulations were performed by Stochastic Monte Carlo Simulations (SAMC).

 

Location: MLU, Von-Danckelmann-Platz 3, SR E.04
Time: 3.30pm-5.00pm

Talk by Ruth Bärenwald at MLU (December 12, 2017)

Solid state NMR investigations and MD simulations of amphiphilic triblock copolymers in lipid bilayers

Pluronics are triblock copolymers widely used in pharmacological industry that consist of hydrophilic poly(ethylene oxide) end blocks and a hydrophobic poly(propylene oxide) middle block. Depending on the lengths of the different blocks, Pluronics can influence membrane properties in a variety of ways.

Using solid-state nuclear magnetic resonance (NMR), we investigated the structure and dynamics of different Pluronics interacting with a number of phosphatidylcholine membranes with variable bilayer thickness and acyl chain saturation. Continue reading “Talk by Ruth Bärenwald at MLU (December 12, 2017)”

Talk by S. Link at MLU (November 14, 2017)

UV-B induced changes of eye-lens crystallins

Age related cataract is the major cause of blindness worldwide. With the age of 75 years, more than 50% of all people are affected and so far, surgery is the only effective treatment available. For this reason it is important to understand the complex system of the eye lens especially effects of aging like chronic UV-B irradiation.

Many modifications of crystallins by UV-B on already aggregated and destroyed protein have been found. So far, changes in the soluble fractions of the protein are not well investigated. Answering this question, different techniques of solution NMR have been applied to native and irradiated hgD-crystallin to identify and characterize a modified but still soluble state of the protein. This would highlight the first structural changes on the transition from functional soluble protein to dysfunctional aggregates.

Location: MLU, Von-Danckelmann-Platz 3, SR 1.06
Time: 3.30pm

Talk by F. Frenzel at UL (October 24, 2017)

Molecular Dynamics and Charge Transport in highly-conductive Polymeric Ionic Liquids

Glassy dynamics and charge transport are studied for the polymeric ionic liquid (PIL) poly[tris(2-(2-methoxyethoxy)ethyl)ammonium acryloxypropyl sulfonate] (PAAPS) with varying molecular weight (9700, 44200, 51600, and 99500 g/mol) by broadband dielectric spectroscopy (BDS) in a wide frequency (10−2−107 Hz) and temperature range (100−400 K) and by DSC- and AC-chip calorimetry.

The dielectric spectra are characterized by a superposition of (i) relaxation processes, (ii) charge transport, and (iii) electrode polarization. Continue reading “Talk by F. Frenzel at UL (October 24, 2017)”

Talk by C. Sungkapreecha at MLU (September 5, 2017)

Phase behavior of polymer/mosquito repellent system PLA/DEET

The phase diagram of the binary polymer/mosquito repellent system poly (lactic acid) (PLA) and N,N-diethyl-3-methylbenzamide (DEET) has been established for the purpose of screening the potential use of biodegradable PLA as drug-delivery reservoir for DEET. Crystallization-induced solid-liquid (S-L) phase separation occurs on sufficiently slow cooling of liquid solutions containing crystallizable PLA at temperatures slightly higher than ambient. Non-isothermal crystallization starts spherulitically at point-like nuclei, followed by dendritic crystal growth due to depletion of crystallizable polymer in the solution in the later stage. Continue reading “Talk by C. Sungkapreecha at MLU (September 5, 2017)”

Talk by T. Thalheim at UL (August 15, 2017)

Thermophoretic trapping of single molecules

We recently developed a tool which confines Brownian motion by generating temperature gradients – the actual fuel of Brownian motion – with the help of plasmonic structures. The physical phenomenon behind this trapping principle is known as thermophoresis or Ludwig-Soret effect. We are also able to control the number of particles interacting in our trap using an optical feedback algorithm which allows us to set up completely new types of bio-molecular interaction dynamics assays.

I will present results of a single λ-DNA molecule whose center of mass (COM) was trapped. Continue reading “Talk by T. Thalheim at UL (August 15, 2017)”

Talk by M. Schäfer at MLU (July 18, 2017)

NMR investigations of dynamics in the different phases of semicrystalline polymers

The melt-crystallized morphology of semicrystalline polymers strongly depends on the diverse dynamics in the amorphous and crystalline region. The connections between structure formation and dynamics of polymer chains are investigated with SAXS and NMR spectroscopy, respectively, comparing polymers with and without intracrystalline dynamics (crystal-mobile and crystal-fixed). Proton time-domain techniques enable the analysis of the phase components, the intracrystalline and the amorphous phase dynamics. Continue reading “Talk by M. Schäfer at MLU (July 18, 2017)”

Talk by T. John at UL (June 13, 2017)

Amyloid peptide aggregation near gold interfaces and membranes

The aggregation of peptides into amyloid fibrils, desired or undesired, plays an important role in biological systems. Amyloid-forming peptides are soluble in its native state and aggregate under certain circumstances via intermediates to insoluble fibrils with characteristic cross-β-sheet structure. This aggregation is believed to be connected with several neurodegenerative disorders such as Alzheimer’s disease (AD). However, it is not yet clear if the oligomeric intermediates or the mature fibrils are the toxic species or if amyloid fibrils are just a side product in the development of these diseases.

Continue reading “Talk by T. John at UL (June 13, 2017)”

Talk by M. Schulz at MLU (May 16, 2017)

Effects of the αC-relaxation for PEO and POM: Impact on Crystallization Process, Morphology and Reorganization Behavior

Depending on the presence or absence of an αC-relaxation it is possible to distinguish between crystal-mobile and crystal-fixed semi-crystalline polymers. Only crystal-mobile polymers own a certain chain mobility in the crystalline phase. In contrast to the crystal-fixed polymer Polycaprolactone (PCL), we analyze the impact of the αC-relaxation for two representatives of αC-mobile polymers, Polyethylenoxide (PEO) and Polyoxymethylene (POM), using different methods like SAXS and Flash-/DSC.

Continue reading “Talk by M. Schulz at MLU (May 16, 2017)”

Talk by F. Hoffmann at MLU (April 4, 2017)

Competition between Electrostatic and Hydrophobic Forces in the Central Core Region of Amyloid β Fibrils

Amyloidogenic peptides aggregated to large molecular assemblies are a hallmark of several diseases including Parkinson’s, Huntington’s, and Alzheimer’s disease as well as type II diabetes. Although each of these diseases gives rise to a very distinctive clinical picture, amyloid fibrils share the cross-β structure as a common structural motif. Within this motif, the peptide strands are linked via lateral β-sheet-turn-β-sheet structures that result in fiber-like aggregates with diameters of a few nanometers and lengths up to several micrometers.

The central question that will be addressed is how electrostatic and hydrophobic interactions compete within the central core region of Aβ(1-40) fibrils. Continue reading “Talk by F. Hoffmann at MLU (April 4, 2017)”