Effect of electric field on structure and dynamics of bilayers formed from anionic phospholipids

AbstractThe effect of molecular structure on ensemble structure and dynamics of phospholipid bilayers has been investigated. Bilayers of dimyristoyl phosphatidylserine (DMPS) supported on Au(111) surfaces were prepared by Langmuir-Blodgett and Langmuir-Schaeffer deposition and studied with a combination of electrochemical measurements and in situ Polarisation Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS). DMPS bilayers have relatively large capacitance when compared with those formed from similar molecules and this is attributed to a high solvent content within the bilayer, resulting from the need for solvation of the negatively charged lipid headgroups. Infrared spectra show that the ensemble of molecules is in a gel state, with extended and ordered hydrocarbon chains, similarly to bilayers of dimyristoyl phosphatidylethanolamine (DMPE) molecules, which are of similar shape. The infrared spectra also show that, in contrast to DMPE, the headgroups of DMPS are very strongly hydrated and have higher mobility. This higher mobility allows the re-orientation of the molecules under the influence of an applied electric field: re-orientation both of headgroups and hydrocarbon tail groups is observed. Thus the shape and charge of the molecules in an ensemble have a strong influence on both their structure and dynamics in the presence of an externally applied electric field

Computational study of the adsorption of benzene and hydrogen on palladium–iridium nanoalloys

SSCI-VIDE+ECI2D+LPIInternational audienceThe preferred chemisorption sites on a variety of palladium-iridium nanoalloys are determined for benzene and hydrogen molecules. Available sites on the surface of the nanoalloys are explored using a random-search method, directly at the density functional level of theory. These searches successfully reveal the site preference for benzene and significant nanosize effects in the chemisorption of hydrogen. It is hoped that through the study of the chemisorption properties of Pd-Ir nanoalloys, complex catalytic processes, such as tetralin hydroconversion and the preferential oxidation of CO, can be better understood. (C) 2015 Elsevier B.V. All rights reserved

Organometallic nucleoside analogues: effect of hydroxyalkyl linker length on cancer cell line toxicity

A new series of chiral ferrocene derivatives containing both a hydroxyalkyl group and a thyminyl group on one cyclopentadienyl ring have been synthesised to probe structure–activity relationships in cancer cell line cytotoxicities. The stereoisomers of enantiomeric pairs of these so-called ferronucleosides have been studied and characterised by a combination of chiral analytical HPLC and single-crystal X-ray diffraction. Biological activity studies revealed that changing the length of the hydroxyalkyl group had marked effects on IC50 values, with compounds having shorter arms that more closely resemble endogenous nucleosides exhibiting lower cytotoxicities. The lipophilicities and electrochemical properties of this compound series have been studied to rationalise these trends and indicate future directions of study