Air-Stable and Catalytically Active Phosphinous Acid Transition-Metal Complexes

Kurscheid B, Lhoussaine B, Hoge B. Air-Stable and Catalytically Active Phosphinous Acid Transition-Metal Complexes. Organometallics. 2011;31(4):1329-1334

Stimulus analysis of BetP activation under in vivo conditions

The secondary active, Na+ coupled glycine betaine carrier BetP from Corynebacterium glutamicum BetP was shown to harbor two different functions, transport catalysis (betaine uptake) and stimulus sensing, as well as activity regulation in response to hyperosmotic stress. By analysis in a reconstituted system, the rise in the cytoplasmic K+ concentration was identified as a primary stimulus for BetP activation. We have now studied regulation of BetP in vivo by independent variation of both the cytoplasmic K+ concentration and the transmembrane osmotic gradient. The rise in internal K+ was found to be necessary but not sufficient for BetP activation in cells. In addition hyperosmotic stress is required for full transport activity in cells, but not in proteoliposomes. This second stimulus of BetP could be mimicked in cells by the addition of the amphiphile tetracaine which hints to a relationship of this type of stimulus to a change in membrane properties. Determination of the molecular activity of BetP in both cells and proteoliposomes provided experimental evidence that in proteoliposomes BetP exists in a pre-stimulated condition and reaches full activity already in response to the K+ stimulus. (C) 2013 Elsevier B.V. All rights reserved

Controlling the self-assembly of magnetic nanoparticles by competing dipolar and isotropic particle interactions

Control over the self-assembly of magnetic nanoparticles (MNP) into superstructures due to different types of coupling is of interest in the development of bottom-up fabrication schemes. Here we realize a simple strategy for the systematic variation of particle interaction potential in magnetic nanoparticles. This is achieved by varying the effective surface potential by means of a co-surfactant introduced in the course of the synthesis process. As a consequence, the ability to form chain-like assemblies is affected by the resulting balance of attractive and repulsive forces. We use electron microscopy, electron diffraction, and light scattering methods to study a series of cobalt nanoparticles as a characteristic example of ferromagnetic MNP. We demonstrate experimentally and substantiate theoretically that the observed behavior results from a balance between magnetic dipole-dipole, steric, and electrostatic interactions. (C) 2014 Elsevier Inc. All rights reserved

Structural Analysis of a Modern o/w-Emulsion Stabilized by a Polyglycerol Ester Emulsifier and Consistency Enhancers

The aim of our work was to study the structure of a typical modern cosmetic oil-in-water emulsion (o/w-emulsion), based on the emulsifier polyglyceryl-3 dicitrate/stearate and glycerylstearate/stearyl alcohol as consistency enhancer. We have used a systematic approach building up the cosmetic emulsion step by step, characterizing all systems by using Small Angle Neutron Scattering (SANS), Differential Scanning Calorimetry (DSC), Freeze Fracture Transmission Electron Microscopy (FF-TEM), light microscopy and rheology. The starting point was the pure emulsifier in water, which was shown to form lamellar stacked bilayers with a spacing of 7 nm, coexisting with polydisperse unilamellar vesicles in the sub-mu m range. Upon addition of consistency enhancer, also multilamellar vesicles could be obtained. Then, oil has been added stepwise, until finally a complete cosmetic o/w-emulsion was obtained. In the final emulsion, oil droplets with sizes in the mu m range are surrounded by multiple, irregularly spaced bilayer structures and vesicles. Approximately 30% of the water present in the system shows a restricted mobility (encapsulated water) according to PFG-NMR. Crucial for the viscosity build-up is the presence of the oil droplets; a cream-like consistency is obtained by steric interaction of oil droplets and crystalline bilayer structures in the aqueous phase of the emulsion