arXiv subjects

Stefan Hobai

Publications and source records attributed to Stefan Hobai.

3 recordsLinked to original sources

arXiv2001

An approximate cooperativity analysis by DSC of phase transitions of DPPC-DOCNa dispersions

The effect of solute, sodium deoxycholate bile salt (DOCNa), on the cooperativity of ordered-fluid, fosfolipid phase transition has been investigated by determining of the transition widths in multibilayer dispersions of the dipalmitoylphosphatidylcholine (DPPC)-DOCNa mixtures. The DT1/2 values were determined by differential scanning calorimetry. The van't Hoff values of the main transition enthalpies were calculated using an approximative expression, deduced from Zimm and Bragg theory [Sturtevant,J.M.(1982), Proc.Natl.Acad.Sci.USA,79:3963-3967]. The bile salt decreases the cooperativity (size of cooperative unit) of DPPC bilayers.

physics.chem-ph↗

arXiv2001

Determination of apparent activating energy of solubilizing MLV-DPPC and MLV-egg-yolk lecithin with surfactants by rectangular optic diffusimetry

It were determinated the apparent activating energy of dipalmitoylphosphatidylcholine (DPPC) multilamellar liposome (MLV) solubilizing with sodium deoxycholate (DOCNa) by turbidi-metric measurements and the apparent activating energy of egg-yolk lecithin (EYL)- MLV solubilizing with different surfactants (DOCNa, TX-100, CTMB) by rectangular optic diffu-si-met-ric measurements. The apparent activating energy of MLV-DPPC solubilizing with DOCNa is Ea = 127.7kJ/mol. The apparent activating energy of MLV-EYL solubilizing with cetyl-trimet-hylamonium bromide (CTMB) is 22.3kJ/mol and with DOCNa is 47.3kJ/mol (average value) and with Triton X-100 is 99.3kJ/mol. On the basis of the above data it can be said that besides the utilisation of the liposomes in the modelling of cellular membranes, they can be used as experimental models, too, in order to investigate the solubilization capacity of surfactants.

physics.chem-ph↗

arXiv2001

Kinetics of solubilization with Triton X-100 of egg-yolk lecithin bilayers containing cholesterol

The titration solubilization of multilamellar egg-yolk lecithin liposomes (MLV-EYL) with Triton X-100 was studied by rectangular optical diffusimetric measurements as a function of cholesterol (Chol) concentration. It was determinated the variation of optic percentage diffu-sion (per mmol surfactant), DDif%/mmol TX-100, in the course of solubilization of MLV-EYL-Chol system with TX-100 10mM. The statistical analysis of the titration curves can reveal the contribution of cholesterol to the stability of phospholipid bilayer membranes. The solubilization of the lecithin-cholesterol mixtures, with a high cholesterol content, much more bile salt requires.

physics.chem-ph↗