A study of the association of organic acids with human serum albumin

Abstract

U.V./Visible spectral changes accompanying the interactions of some organic acids with human serum albumin have been studied in detail.

The spectra have been analysed by means of matrix rank analysis to estimate the number of spectrophoto-metrically distinguishable species in solution. This may be used to estimate the number of distinct classes of binding sites on the albumin molecule.

A new method has been developed to obtain equilibrium constants and numbers of binding sites per albumin molecule from spectrophotometric data.

The method involved the titration of a constant concentration dye solution with human serum albumin. The series of spectra thus obtained were analysed by means of a computer assisted data fitting routine. The routine was based on a model for the system, using two independent classes of binding sites on the albumin molecule. A series of derivatives of azobenzene were studied by the method in order to correlate structural features of the molecules with the extent to which they bound to human serum albumin.

The interactions of the azobenzene derivative series, with human serum albumin, were studied by an ultrafiltration technique. Projected ultrafiltration binding curves from the U.V./visible spectrophotometric experiments were found to be in agreement with those measured experimentally.

Spectral changes accompanying the competitive interactions between Bromophenol Blue, and the azobenzene10derivatives, with human serum albumin, have also been studied. An attempt has been made to correlate these results with the foregoing binding experiments.