Electrophoresis of adsorbed albumin

Abstract

AbstractIt was recently observed that bovine serum albumin (BSA), adsorbed onto part of the surface of a glass slide, diffuses along the unoccupied part of that surface (without redissolving in the bulk liquid) at a much greater velocity than the normal diffusion rate of BSA, free solution. In this work a study is made of the electrophoretic transphoretic transport of BSA, adsorbed onto part of the surface of glass slide, along the hitherto unoccupied part of the glass surface. The electrophoretic mobility of adsorbed BSA along the unoccupied glass surface proved to be up to ≅ 2 times faster than in electrophoresis on cellulose acetate strips at the same pH and ionic strength, and up to ≅ 1.6 times faster than in moving boundary electorphoresis. The increase in electrophoretic mobility of adsorbed BSA is most pronounced at the highest density of adsorption. At that density the oblong BSA molecules are closely packed, most probably adsorbed in a tight monolayer, with each molecule positioned perpendicular to the glass surface (although other configurations cannot be excluded). The major driving force enhancing the diffusivity, as well as the electrophoretic mobility of adsorbed BSA, appears to be the high surface pressure of he tightly packed BSA layer. A tentative explanation is offered for the low resistance BSA molecules encounter in moving parallel to the glass surface while remaining adsorbed to the liquid, involving free energies of adhesion of individual protein molecules in various orientations.