Electrophoretic studies of oxytocin and vasopressin.

Recently a highly potent preparation of vasopressin has been obtained from beef posterior pituitary glands and the amino acid composition of this material has been established (2). Reef vasopressin resembles oxytocin in that six of the eight constituent amino acids are identical; however, vasopressin differs from oxytocin in that it contains arginine and phenylalanine in place of the leucine and isoleucine found in oxytocin. Thus it was considered important to a study of the structure of vasopressin to investigate its electrophoretic properties. The procedure of zone electrophoresis was employed not only to parallel the studies already made on oxytocin (3), but also because this technique permits the direct determination of the activity of the separated components. Earlier results of electrophoretic analysis in free solution of oxytocin and vasopressin materials have shown that the oxytocic and vasopressor activities possessed ifferent rates of migration (4), and that the isoelectric point of vasopressin was at pH 10.85 (5). Recently, Acher, Chauvet, and Fromageot (6) reported that their preparation of beef vasopressin behaved as a single substance on electrophoresis on paper at pH 4 and had the same amino acid composition as that found by Turner, Pierce, and du Vigneaud (2).