The Sedimentation Constant of Visual Purple

Abstract

The sedimentation constant of visual purple measured in the air-driven ultra-centrifuge is Sw2o=ll.l X 10-13 cm/dyne/sec. and is of the same order of magnitude as those found for such proteins as edestin and phycoerythrin. Computed from the sedimentation constant and from the diffusion constant, the molecular wt. of visual purple is about 270,000, provided its density is 1.33 gm./cc. as is that of most proteins. Computed from the sedimentation constant alone its molr. weight is 200,000 so that the molecule is probably not quite spherical. At pH 7.7, the sedimentation constant does not change perceptibly on bleaching. This indicates that light produces no drastic splitting of the molecule.