To understand the complex nanoscale dehydration process during the lower critical solution temperature (LCST) based inverse phase transition of a class of thermoresponsive biopolymers, diblock elastin-like polypeptides (ELPs) were investigated by spin probing continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The diblock copolymers composed of a hydrophobic block and a hydrophilic block showed different mechanisms of a temperature-driven phase transition. While the phase transition temperature is a function of the hydrophobic mass fraction of the diblock ELPs, the hydrophilic block length determines the molecular structure of the polymer aggregates formed above the transition temperature. When the weight ratio of hydrophilic block length to hydrophobic block length is greater than or equal to 0.3, the polymer aggregates consist of a hydrophobic core and a hydrophilic corona. The interface of these two regions become permeable at temperatures above the transition temperature. In case of smaller ratios, the aggregating hydrophobic parts of the polymer enclose the hydrated hydrophilic blocks, that are too small to form a hydrophilic corona, leading to bigger and less dense aggregates of higher polarity.

Interaction of myelin basic protein (MBP) and the cytoplasmic leaflets of the oligodendrocyte membrane is essential for the formation and compaction of the myelin sheath of the central nervous system and is altered aberrantly and implicated in the pathogenesis of neurodegenerative diseases like multiple sclerosis. To gain more detailed insights into this interaction, the adsorption of MBP to model lipid monolayers of similar composition to the myelin of the central nervous system was studied at the air-water interface with monolayer adsorption experiments. Measuring the surface pressure and the related maximum insertion pressure of MBP for different myelin-like lipid monolayers provided information about the specific role of each of the single lipids in the myelin. Depending on the ratio of negatively charged lipids to uncharged lipids and the distance between charges, the adsorption process was found to be determined by two counteracting effects: (i) protein incorporation, resulting in an increasing surface pressure and (ii) lipid condensation due to electrostatic interaction between the positively charged protein and negatively charged lipids, resulting in a decreasing surface pressure. Although electrostatic interactions led to high insertion pressures, the associated lipid condensation lowered the fluidity of the myelin-like monolayer.

PACS. 74.72Bk -Y-based compounds. PACS. 78.00 -Optical properties of condensed-matter spectroscopy and other interactions of PACS. 79.20Kz -Other electron-impact emission phenomena. matter with particles and radiation.

Functionally relevant conformational states of intrinsically disordered proteins (IDPs) are typically concealed in a vast space of fast interconverting structures. Here we present a novel methodology, NMR-based paramagnetic relaxation interference (PRI), that allows for direct observation of concerted motions and cooperatively folded sub-states in IDPs. The proposed NMR technique is based on the exploitation of cross correlated electron-nuclear dipolar relaxation interferences in doubly spin-labeled proteins and probes the transient spatial encounter of electron-nucleus spin pairs.

We have investigated the near-infrared (0.5 -1.5 eV) optical response of quenched YBa2CusOr samples with intermediate oxygen content as a function of the time r the samples spent at room temperature. In a previous experiment, we determined the dielectric function in the spectral region between 3.8 and 4.3 eV under similar conditions using spectroscopic ellipsometry. We find an increase of the concentration of Cu(I) + ions with r, indicating an oxygen-reordering process in the course of which Cu-0 dumbells [linearly coordinated O(IV)-Cu(I)-O(IV) complexes] are generated. The re8ectance measurements in the infrared regime between 0.5 and 1.5 eV indicate that simultaneously additional carriers are generated in the Cu02 planes. Both findings are in accordance with previous explanations of the rise of T with w.