Binding of selected phenol derivatives to human serum proteins

The binding of phenol and four of its derivatives to whole human serum and several human serum proteins was investigated. 14C-labeled derivatives were utilized and binding was studied by either equilibrium or dynamic dialysis. Phenol itself was bound least to most of the serum proteins as compared to the derivatives and albumin, and whole human serum exhibited the highest percent binding of the proteins used. Percent binding to albumin and serum paralleled molecular weights of the derivatives, but not definite pattern was observed in ranking the percent binding of the other derivatives to the other serum proteins. Binding constants (K1, K2, n1 and n2) were determined from Scatchard plots for all the derivatives except p-chloro-m-xylenol. Phenol was found to have the highest association constant (K1) and p-tert-amylphenol, the lowest. For the entire group of five derivatives and albumin as the protein, a direct, statistically significant correlations was found between percent binding and Hansch pi values. No correlation was found with Hammett sigma values. It is concluded that binding of the phenol derivatives to albumin involves primarily hydrophobic bonds.