Category: Doctoral students seminar SoSe 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)”

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)”

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)”

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)”

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

Depending on the presence or absence of an α_C-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 α_C-relaxation for two representatives of α_C-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)”

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)”