Polymer resins with amino acid containing pendants for sorption of bilirubin. IV. Site binding constants.

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 10(4) M-1. 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 pi-pi electron interactions, where applicable.

Polymer resins with amino acid containing pendants for sorption of bilirubin. III. Adsorption and desorption in the presence of albumin.

The adsorption of bilirubin from aqueous phosphate buffer solutions (pH = 7.8) containing bovine serum albumin (BSA) by polyacrylamide resins, with pendants consisting of the oligopeptides (Arg)5(Ala)3-, (Arg)2(Ala)3-, (Lys)5(Ala)3-, His(Arg)2(Ala)3-, has been studied at 0 degrees C under N2. The ability of the oligopeptide-resins to retain adsorbed bilirubin in the presence of BSA follows the order (Arg)5(Ala)3- greater than (Arg)2(Ala)3- greater than (Lys)5(Ala)3- = His(Arg)2(Ala)3-resin. The (Arg)5(Ala)3-resin is able to abstract the second bilirubin on the albumin assuming that BSA binds two bilirubin molecules strongly.

Polymer resins with amino acid containing pendants for sorption of bilirubin. II. Polyamide resins with various basic amino acids.

Short peptides, three to eight amino acids in length, containing various combinations of alanine, arginine, lysine, histidine and tyrosine have been synthesized onto water-swellable polyamide resin by the solid phase peptide synthesis method. The amount of bilirubin adsorbed from aqueous buffer solution (pH = 7.8) by the resins increases with increasing basicity of the amino acids in the pendant. As the number of basic amino acids on the pendant is increased from one to five a 4.7 fold enhancement in the adsorption capacity is seen for arginine while a 9.3 fold enhancement is obtained for lysine. A corresponding increase in length for the non-basic histidine results in a 6 fold enhancement. With alanine the adsorption capacity is uneffected by an increase in pendant length.

Polymer resins with amino acid containing pendants for sorption of bilirubin. I. Comparison of Merrifield and polyamide resins.

Merrifield resins with various amino acid containing pendants and a water swellable polyamide resin with the peptide alanine-alanine-alanine-arginine as the pendant group have been prepared by solid phase peptide synthesis. Merrifield resins with either arginine or lysine pendants are capable of sorbing bilirubin from aqueous solution (pH = 7.8) but those with other amino acid pendants gave no indication of sorption. The polyamide-arginine resin showed, on a functional group basis, a higher capacity for bilirubin than does cholestyramine. It is proposed that the formation of salt linkages causes a strong interaction of bilirubin with arginine and lysine.

The adsorption of bilirubin from aqueous solution onto solid cholestyramine and polyvinylpyrrolidone.

Shifts in the visible spectrum of aqueous bilirubin (BR) resulting from the addition of soluble polyvinylpyrrolidone (PVP) suggest specific interactions. Hence, isotherms were determined for the adsorption of BR from aqueous solution onto solid, cross-linked PVP and onto cholestyramine (CA) (used as a reference adsorbent) at 0, 10, 20 and 25 degrees C. Although adsorption onto PVP reaches equilibrium values more rapidly than for CA, the latter adsorbent has a larger capacity. Furthermore the isotherms for PVP are independent of temperature while those for CA show an increase in BR adsorbed with an increase in temperature.