0000000000733416
AUTHOR
L. Braco
HPLC study on the ‘history’ dependence of gramicidin A conformation in phospholipid model membranes
AbstractA novel HPLC methodology for the study of gramicidin A reconstituted in model membranes has been tested in comparison with circular dichroism data. It is shown that this chromatographic technique not only corroborates most of the recent spectroscopic results but allows one to explain them in terms of mass fractions of different actual conformational species of GA in the phospholipid assemblies. In particular, the dependence of the inserted peptide configuration on the organic solvent and other parameters involved in the ‘history’ of the sample preparation and handling has been analyzed by HPLC in two phospholipid model systems: small unilamellar vesicles and micelles. Moreover, a sl…
A semi-empirical approach for the simulation of circular dichroism spectra of gramicidin A in a model membrane
In an extension of our previous work (Bañó, M. C., Braco, L., and Abad, C. 1991. Biochemistry. 30:886-94), the kinetics of dissociation of gramicidin A double-stranded dimers into beta 6.3-helical monomers in small unilamellar vesicles prepared following different protocols, were investigated using in combination circular dichroism (CD) and high-performance liquid chromatography (HPLC). The analysis of the data from both techniques according to a two-component model strongly supports that any given CD pattern of gramicidin incorporated in the phospholipid bilayer can be deconvoluted essentially as a linear combination of the reference subspectra calculated for the double-stranded dimer and …
Determination of the relative quantum yields of the conformational species of autoassociating polypeptide gramicidin A in organic solvent using combined fluorescence spectroscopy and high performance liquid chromatography
Abstract A simple, novel method is proposed for the accurate determination of the relative quantum yields of each of the interconverting conformational species of the autoassociating polypeptide gramicidin A in organic solution. The method is based on fitting the experimental results obtained independently from fluorescence emission spectroscopy and high performance liquid chromatography. The fluorescence parameters obtained are discussed in terms of the structural features of the individual conformational species. The advantages of this approach and its possible application to other different organic solvents or to other autoassociating polypeptides are also considered.
Spectroscopic and chromatographic study of the interaction of nonionic micelles with the aluminum-morin complex
Abstract The interaction of the aluminum-morin system with different nonionic surfactants has been studied spectrophotometrically and by high-performance liquid chromatography. It has been found that ethylene oxide-propylene oxide condensate surfactants sensitize the spectrophotometric determination of aluminum with morin more than ethylene oxide condensate surfactants. Binding ratio parameters for the different surfactants with free morin have been also estimated from the analysis of chromatographic vacant peaks.