Thermodynamics and kinetics of the neutral transition of human serum albumin, monitored by the spectral change of bound bilirubin.

Sectral changes in the complex of human serum albumin with bilirubin in the neutral pH range are related to conformational alterations of the protein. The transformation responds to changes in temperature and concentration of calcium ions in a similar fashion as the N-B transition of albumin. The kinetics of the structural changes are studied. The spectral shift from high to low, as well as from low to high pH, is presented in a model consisting of three relaxation steps.