[Study on the interaction of bovine serum albumin with bamphenol blue in acidic solution by spectrophotometry].

On the basis of the difference between the absorption spectra of free and bound BPB, the interaction of bamphenol blue (BPB) with bovine serum albumin (BSA) in acidic solution was investigated by a spectrophotometric method. Solutions containing 5.0 x 10(-6) mol.L-1 of dye concentration and various BSA concentrations from 0.5 x 10(-6) to 3.8 x 10(-6) mol.L-1 were prepared in pH 2.79 Britton-robinson buffer, and the absorbances were measured at 605 nm. The result calculated from the above experiments show that the ratio between the average number of dye molecules bound per protein molecule and the concentration of free BPB is approximately constant. So the interaction of BSA and BPB in the experimental conditions selected in this paper can be regarded as a kind of phase distribution. A simple double reciprocal equation for the estimation of apparent binding constant and the maximum binding number was easily derived. The linear regression between the reciprocal of the observed absorbance change at 605 nm due to the addition of BSA to a fixed quantity of BPB (delta A-1) and the reciprocal of the concentration of BSA (CP-1) was made. All of the regression coefficients for the lines of delta A-1 versus CP-1 obtained from various pH values, BPB concentrations and ion strengths were better than 0.99. Through the ratio of intercept and slop, both the apparent binding constants and the maximum binding numbers were calculated for various experimental conditions.