The interaction of alizarin red S and bovine serum albumin was studied by UV spectra in pH 4.35 buffer solution. The binding number (n=8) and binding constant (K~c=1.5×10^5) of the probe and protein were obtained. The main sort of binding force was investigated. It was found that the red shift of isosbestic point of the complex was 28nm and the sodium chloride concentration had significant effect on the binding reaction. The "Phase Distribution Model" is the proper description of the interaction between alizarin S and the protein.

Key words: ULTRAVIOLET SPECTROPHOTOMETRY, REACTION MECHANISM, ALIZARINE RED, PROTEIN, SERUM ALBUMIN