Accession Number:

ADA347541

Title:

Phosphatidylcholine Monolayer Formation at a Liquid:Liquid Interface as Monitored by the Dynamic Surface Tension

Descriptive Note:

Technical rept. 1 Mar 97-31 May 98

Corporate Author:

OREGON UNIV EUGENE DEPT OF CHEMISTRY

Report Date:

1998-05-30

Pagination or Media Count:

50.0

Abstract:

Dynamic surface tension experiments have monitored the rate of phospholipid monolayer formation at a planar aqueousCCl4 interface from a solution of phosphatidylcholine PC vesicles. The rates at which monolayers form show that monolayer formation is a barrier controlled rather than a diffusion controlled process. At sufficiently low bulk PC concentrations, monolayer formation kinetics are first order in aqueous PC concentration. The kinetics can be described by a rupture mechanism which postulates that vesicles disintegrate at the aqueousCCl4 boundary allowing all of the monomers to adsorb to the interface. When coupled to an appropriate two dimensional equation of state this mechanism quantitatively models the observed dynamic surface tension data. Solutions of vesicles in their liquid crystalline phase form tightly packed monolayers at concentrations above approx. 2 micro Molar, while solutions of gel phase vesicles form expanded monolayers regardless of bulk PC concentration. From the Arrhenius behavior of the dynamic surface tension data, we find that the barrier to monolayer formation is larger for solutions of liquid crystalline vesicles than for solutions of gel state vesicles. These phenomena - the extent of monolayer formation and Ea for monolayer formation - support a model which describes monolayer formation as a thermodynamically driven transformation from monomers within a bilayer to monomers adsorbed at the aqueousCCl4 interface.

Subject Categories:

  • Biochemistry
  • Organic Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE