Five-component dielectric dispersion in bovine serum albumin solution

Abstract

Dielectric measurements were made on aqueous solutions of native BSA [bovine serum albumin] monomers at 3 concentrations and at about 80 separate frequencies in the range 0.03-800 MHz. All measurements were made at 25.degree. C on solutions of pH = 5.0, this being near the isoelectric point. The analysis shows the presence of a double component .beta. dispersion at frequencies below 10 MHz plus 2 .delta. dispersions with relaxation frequencies of around 15 MHz and 100 MHz. The origin at a molecular level of the .beta. and the higher frequency .delta. dispersion can be established with confidence but the remaining .delta. dispersion cannot be interpreted unambiguously. With the inclusion of the well known .gamma. dispersion at frequencies in excess of 1 GHz the measurements indicate the existence of 5 clearly separated dispersion regions. This is one more dispersion than previously suggested in the literature for a protein solution of this nature.