The double-layer electric repulsion and dispersion attractive interactions between bovine serum albumin(BSA) molecules in aqueous NaCl solution are represented by a Yukawa potential and a Lennard- Jones potential, respectively, instead of the classical DLVO theory. Based on the osmotic McMillan-Mayer statistical theory, a new equation of state (EOS) is proposed in combination of a Yukawa EOS of Duh and Mier-Y-Teran with a perturbed LJ equation of Cotterman etc. to correlate and predict the osmotic pressure data of aqueous BSA solution with NaCl. The result from the correlation of BSA in 0.15 mol/L NaCl aqueous solution can be used to predict the osmotic pressure of BSA in 1～5 mol/L aqueous NaCl solution. Two adjustable parameters (hard-sphere diameter σ and LJ parameter ε/k) are used in this EOS with good correlation and prediction results. A comparison with other theories is also discussed.

Key words: SERUM ALBUMIN, SODIUM CHLORIDE, OSMOTIC PRESSURE