MULTIVARIATE-ANALYSIS OF THE ASSOCIATION OF BROMOCRESOL PURPLE ANION WITH BOVINE SERUM-ALBUMIN

The interaction of bromocresol purple (BCP) anions with bovine serum a lbumin (BSA) was investigated by principal factor analysis method, and reaction model, the number of molecular species and spectra of each c omponent present in the reaction mixture were determined. The number o f molecular species concerning the absorption intensity was three, inc luding free BCP anion. Most part of the spectral change could be expla ined by the monomer binding of bromocresol purple anion (D) to serum a lbumin (P), a simple one step equilibrium, P + D = PD. A second type o f association of BCP anions with serum albumin was also present, thoug h in a small amount. Of six models tested which consisted of three or four molecular species, the sequential two step reaction model, P = PD = PD2, was the best model to explain the spectral data, and an existe nce of BCP anions as a dimer on the serum albumin was demonstrated. Th e dissociation constants were estimated at K-1 = 1.6 x 10(-6) M for th e first step and K-2 = 1.2 x 10(-5) M for the second step. (C) 1997 El sevier Science B.V.