Evidence for distinct consecutive steps in the neutral to base transition of human serum albumin

The neutral to base transition in human serum albumin has been studied by means of circular dichroism and equilibrium dialysis using nitrazepam as the non-covalently bound circular dichroic probe. Spectroscopically two transitions were observed over the pH range 5.5-8.5, whereas dialysis data point to only one transition occurring in the latter part of the pH region studied. Both pH dependences could only be correlated if it is assumed that the neutral to base transition consists of at least two distinct consecutive steps.