1. Whole bovine albumin, homogeneous in diffusion and sedimentation, and essentially homogeneous in electrophoresis, has been prepared by a method involving ammonium sulfate precipitation of the globulins in the cold and of the albumin at room temperature, isoelectric precipitation of the euglobulins, and reprecipitation of the albumin.
2. The product has been characterized by chemical analysis and by viscosity, diffusion, sedimentation, and electrophoresis measurements. The carbohydrate content is 0.38 per cent, the nitrogen content, 15.2 per cent. The molecular shape approximates that of a prolate ellipsoid with an axial ratio of 3.1, assuming 33 per cent hydration; the average molecular weight is 65,000.
3. Bovine albumin is readily denatured by concentrated solutions of urea or guanidine hydrochloride, gross changes in molecular shape resulting.
4. Regeneration of bovine albumin denatured in solutions of 8 M urea or guanidine hydrochloride yields a material closely resembling the native in carbohydrate content, in molecular size and shape, and in electrophoretic properties. However, the regenerated protein differs from the native in susceptibility to tryptic digestion, and, in this respect, appears to be in a denatured state.
5. In 8 M solutions of guanidine hydrochloride a limiting yield of regenerated albumin equivalent to 95 per cent of the original protein is approached.
6. Bovine crystalbumin, a crystalline carbohydrate-free fraction of the whole albumin, appears to be more susceptible to denaturation than whole bovine albumin.
The oncornavirus glycoprotein gp69/71: a constituent of the surface of normal and malignant thymocytes.
