Deriving Equations to Account Quantitatively for the Effect of Neutral Salts on the pH of lsoionic Bovine Serum Mercapt-albumin without Assuming Anion Binding

University College of Science. Department of Chemistry, Calcutta-700009 Manuscript received 29 July 1975, accepted 22 September 1975 As protein molecules at a concentration of about 0.2 per cent can cover the surface of particles of glass, quartz etc. so it has been assumed that the surface of a glass electrode, placed in a solution of concentration above 0.7 per cent of bovine serum mercapt-albumin (BSA) at isoionic pH or above it, is almost completely covered by the protein molecules. On the basis of this assumption and the theory of colloidal electrolytes proposed by the author equations have been deduced which can quantitatively account for the rise in pH of isoiouic (BSA) caused by the additon of neutral salts, without assuming anion binding. It has also been shown that the number of proton donors per mole of (BSA) (molecular weight 69,000), dissociating in the pH range 5.1 to about 7 S, is 12.6 and their pK is 6.18