Polymer Resins with Amino Acid Containing Pendants for Sorption of Bilirubin. IV. Site Binding Constants

Abstract

Site binding constants, calculated for the adsorption of bilirubin onto various lysine, arginine, or histidine containing oligopeptide-resins assuming either a one or two site binding model, are of the order of ^{104 M}. Using these data it can be shown that there are positive cooperative effects for lysine-containing pendants, while arginine-containing pendants eventually result in negative cooperative behaviour. This difference in behaviour has been attributed to the difference in the side groups in the arginine and lysine pendants and is discussed in terms of the basicity of the amino acids, accessibility to the sites as a consequence of the flexibility or rigidity of the side group, and in terms of π-π electron interactions, where applicable.