Vasopressin electrophoresis

Small amounts of vasopressin (1.67 p/ml) and oxytocin (1.5-15 p/ml) are found in the plasma of normal humans. It is not known in what form the active polypeptides are carried in the plasma, but it has been suggested that the polypeptides are bound to a plasma protein which on block starch-gel electrophoresis migrates in front of the major fractions of globulin. 

As already discussed neurophysin-M consisted of two protein components separable by electrophoresis. One of the two constituents occurred in neurosecretory granules and the other appeared to be a degradation product. When attempts were made to separate them by fractional precipitation in the presence of vasopressin by the addition of increasing amounts of salt the proportion of the two remained constant. However, after a few days the amorphous precipitate kept at crystallized. This was interesting because it was the first time that vasopressin had been obtained in crystalline form 26, The need to separate the two proteins in neurophysin-M was removed when it was found that only one of them was present in extracts of an acetone powder of pituitary tissue. 

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