THE EFFECT OF ISOELECTRIC AMINO ACIDS ON THE pH OF A PHOSPHATE BUFFER SOLUTION : A CONTRIBITTION IN SUPPORT OF THE "ZWITTER ION" HYPOTHESIS.
The relative merits of the classical conception and of the Zwitter Ion conception of the dissociation of amphoteric electrolytes are discussed, and the following data are presented which confirm the Zwitter Ion hypothesis of Bjerrum, and which are not in accord with the classical view. 1. Amino acids in the isoelectric form resemble strong electrolytes in that they contribute to the ionic strength of the solution. 2. The dielectric constants of aqueous solutions of amino acids, like those of solutions of strong electrolytes greater than 0.02 normal, are considerably greater than that of pure water. 3. The magnitude of the dissociation constants of substituted acetic acids and of glycine, are more easily accounted for with the Zwitter Ion than with the classical conception.
Borsook
H
H
Department of Biochemistry, University of Toronto, Toronto, Canada, and the Kerckhoff Biological Laboratories, California Institute of Technology, Pasadena, California.
Macfadyen
D A
DA