Evidence for differences in the binding of triton X-100 to sheep and human serum albumins

The binding of triton X-100 to bovine serum albumin has been shown to exhibit positive cooperativity. Subsequent equilibrium dialysis studies indicate that the binding of Triton X-100 to sheep serum albumin likewise shows positive cooperativity, the first two stepwise equilibrium constants being K1 = 1.24 X 10(4) M-1 and K2 = 1.62 X 10(4) M-1. However, the mechanism for Triton X-100 binding to human serum albumin differs in that the binding isotherm indicates the binding sites are independent and identical. In the latter case the binding is described by the Scatchard model with an equilibrium constant of K = 7.2 X 10(3) M-1. The studies were conducted at 16 degrees C in pH 7.0, I = 0.05 phosphate buffer.