title: A two-constant equation for multiple albumin-binding isotherms.
abstract: It has been found that binding of low molecular weight ligands to human serum albumin is generally nonsaturating. Equations commonly used for describing the binding equilibria, i.e., the Scatchard and Klotz (Adair) equations, are saturation functions. We have accordingly tried to establish an equation which would fit the observed data, i.e., not reach a saturation plateau. An empirical equation, in which the bound ligand is expressed as a function of the free ligand [R(C) = b1 in (b2C + 1)], is shown to give reasonably good fits to observed binding equilibrium data for the binding of several organic ligands to human serum albumin, when the two parameters, b1 and b2, are given suitable values. The curve of bound versus free ligand, as plotted from this equation, has the same slope and curvature as that obtained from the Klotz stepwise binding equation at C = 0, if b1 = K1/[2(K1 - 2K2)] and b2 = 2(K1 - 2K2), where K1 and K2 are the first and second stoichiometric binding constants.
mesh_terms: D000418:Albumins / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006801:Humans; D007700:Kinetics; D013816:Thermodynamics
chemical_list: D000418:Albumins