Physico-chemical Approach to Biopharmaceutical Phenomena. I. Adsorption of Tryptophan from Aqueous Solution

概要

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The adsorption of trytophan by carbon black from aqueous solution was studied for an approach to an understanding of biopharmaceutical phenomena, comparing with the adsorptions by keratin, silica gel and graphite. The stereoselective adsorption, which took place on keratin, was not observed in the case of carbon black. The interaction of tryptophan with the carbon black surface might be originated by the orientation of hydrophobic moiety on the surface, being free from steric hindrance of the other moiety. While the amount of tryptophan adsorbed on silica gel increased with the acidity, the adsorption by carbon black did not depend distinctively on pH in the region of pH 3 to 9,though some part of the carbon black surface was considered to have a polarity. Tryptophan might be adsorbed preferentially on the nonpolar part of the surface where the indole group adopted the parallel orientation. The adsorption of tryptophan by carbon black increased with temperature. In order to discuss this unusual phenomenon, the thermodynamic functions were calculated, showing the entropy effect was predominant in the course of adsorption. It was suggested that the adsorption in this system might be forced with the entropy increase through the change of water structure caused by break-down of the iceberg enclosing the tryptophan molecule in solution.
公益社団法人日本薬学会の論文
1968-11-25