Fluorescein binding to normal human serum proteins demonstrated by equilibrium dialysis

The binding of fluorescein to normal human serum proteins in a physiologic solvent at 37 degree C was measured by equilibrium dialysis. Human serum contained 3.28 X 10(-3)M concentration fluorescein-binding sites, with an average association constant at 37 degree C of 0.54 X 10(4)M(-1). The percentage of total fluorescein bound by human serum proteins ranged from 83% to 53% when the total fluorescein concentration ranged from 6.9 X 10(-5) to 6.2 X 10(-3)M.