Five-component dielectric dispersion in bovine serum albumin solution.

Dielectric measurements were made on aqueous solutions of native BSA monomers at three concentrations and at about eighty separate frequencies in the range 0.03-800 MHz. All measurements were made at 25 degrees 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 two 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 five clearly separated dispersion regions. This is one more dispersion than previously suggested in the literature for a protein solution of this nature.