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From a consideration of amino acids as ammono compounds it would seem likely indeed that liquid ammonia would be a most suitable solvent for the study of not only these substances, but also of the simple derivatives of the amino acids and possibly for the investigation of the more complex derivatives, the proteins. A study of the solubilities of a number of amino acids in liquid ammonia showed they were quite soluble in most instances. Of particular interest to us was the ready solubility of cystine in this medium, in contrast to its behavior in water. In view of this fact it was decided to investigate the possibility of the reduction of cystine to cysteine, the sulfhydryl form, by means of metallic sodium. It was found that this reaction readily takes place and, in fact, affords an excellent method for the preparation of cysteine.

The reversible inactivation of tobacco mosaic virus by crystalline ribonuclease is reported. Studies on the effect of time of standing on the amount of inactivation, and on the effect of dilution and repeated high speed centrifugation on the recovery of virus activity, and the preparation of an insoluble virus-enzyme complex show that the inactivation is brought about at least in part by a combination between virus and enzyme. The significance of the fact that ribonuclease has no detectable effect on the virus nucleic acid when the latter is in combination with protein in the form of virus is discussed with respect to the structure of the virus.

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