B-11 NUCLEAR-MAGNETIC-RESONANCE STUDIES OF THE INTERACTION OF BOROCAPTATE SODIUM WITH SERUM-ALBUMIN

The interaction between borocaptate sodium, Na2B12H11SH (BSH), and thr ee types of serum albumin-bovine, human and dog (BSA, HSA and DSA)-has been investigated quantitatively using B-11 NMR. The B-11 chemical sh ifts and relaxation rates of BSH were studied with various concentrati ons of serum albumin (1-5%, w/v) at 295-310 degrees K. Correction of t he longitudinal relaxation rate (R(1)) due to protein viscosity effect s was accomplished. The corrected R(1) values were analyzed mathematic ally using a saturation function and linear regression. The linewidths of B-11 resonances, which are related to the spin-spin relaxation rat es (R(2)), were also measured. The binding fractions (P), the number o f binding sires (NBS), and the binding constants (K-b) of BSH at vario us concentrations of the three types of serum albumin (1-5%, w/v) were determined at 295 and 310 degrees K. We speculate that the nature of this interaction may be electrostatic.