Charge-transfer and water-mediated adsorption. III. Adsorption on tryptophan-substituted Sephadex and Sepharose.

The adsorption of tyrosine, tryptophan and some related compounds on tryptophan and tryptophanyltryptophan gels is similar to but much stronger than that observed with the parent gel Sephadex G-25. The adsorption has been attributed mainly to charge transfer or redistribution of electrons and protons leading to pi-bonding and hydrogen bonding, in addition to hydrophobic adsorption. The participation of organized water surrounding the gel matrix, the ligands and the solute molecules has been considered. The application of this principle of adsorption has been exemplified by chromatographic experiments with a cellulase preparation of tryptophan-Sepharose 4B.