Formation and nanoscale characterization of asymmetric supported lipid bilayers containing raft-like domains

The development of new strategies for achieving stable asymmetric membrane models has turned interleaflet lipid asymmetry into a topic of major interest. Cyclodextrin-mediated lipid exchange constitutes a simple and versatile method for preparing asymmetric membrane models without the need for sophisticated equipment. Here we describe a protocol for preparing asymmetric supported lipid bilayers mimicking membrane rafts by cyclodextrin-mediated lipid exchange and the main guidelines for obtaining structural information and quantitative measures of their mechanical properties using Atomic force microscopy and Force spectroscopy; two powerful techniques that allow membrane characterization at the nanoscale.Fil: Vazquez, Romina Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; ArgentinaFil: Ovalle García, Erasmo. Universidad Nacional Autónoma de México; MéxicoFil: Antillón, Armando. Universidad Nacional Autónoma de México; MéxicoFil: Ortega Blake, Iván. Universidad Nacional Autónoma de México; MéxicoFil: Muñoz Garay, Carlos. Universidad Nacional Autónoma de México; MéxicoFil: Maté, Sabina María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; Argentin

Coupling a polarizable water model to the hydrated ion–water interaction potential: A test on the Cr3+ hydration

A strategy to build interaction potentials for describing ionic hydration of highly charged monoatomic cations by computer simulations, including the polarizable character of the solvent, is proposed. The method is based on the hydrated ion concept that has been previously tested for the case of Cr3+ aqueous solutions [J. Phys. Chem. 100, 11748 (1996)]. In the present work, the interaction potential of [Cr(H2O6)]3+ with water has been adapted to a water model that accounts for the polarizable character of the solvent by means of a mobile charge harmonic oscillator representation (MCHO model) [J. Chem. Phys. 93, 6448 (1990)]. Monte Carlo simulations of the Cr3+ hexahydrate plus 512 water molecules have been performed to study the energetics and structure of the ionic solution. The results show a significant improvement in the estimate of the hydration enthalpy [ LlHhydr(Cr3+)=-1109.6:±70 kcal/mol] that now matches the experimental value within the uncertainty of this magnitude. The use of the polarizable water model lowers by �140 kcal/mol the statistical estimation of the [Cr(H2O6)]3+ hydration enthalpy compared to the nonpolarizable model. (-573 kcal/mol for the polarizable model vs -714 kcal/mol for the nonpolarizable one.) This improvement reflects a more accurate treatment of the many-body nonadditive effects.Dirección General de Investigaciones Científica y Técnica PB95-0549DGAPA-UNAM ES-112896CONACyT L004-

自称表現に見られる日中両言語の人称代名詞と親族語彙

千葉大学社会文化科学研究科研究プロジェクト報告書第84集『日中両言語における代名詞及び親族語彙の対照研究-琉球方言との比較研究も含めて』所

Amphotericin B Channels in the Bacterial Membrane: Role of Sterol and Temperature

Amphotericin B is an antibiotic that forms ion channels in the membrane of a host cell. The change in permeability produced by these channels is greatly improved by sterols; nevertheless, the single channel conductivity remains invariant. Hence, it is proposed that sterols do not act directly, but rather through the modulation of the membrane phase. We look at the formation of these channels in the bacterial membrane to determine the mechanism of its known antibiotic resistance. We found that channels can indeed be formed in this membrane, but a substantial amount of amphotericin B is required. We also study the effects of the antibiotic concentration needed for channel expression as well as the dynamics of channels affected by both sterol and temperature in phosphatidylcholine membranes. The results support the idea that membrane structure is a determining factor in the action of the antibiotic