THE LS-ANTIGEN OF VACCINIA IV. CHEMICAL ANALYSIS O~" LS AND TIlE EFFECT OF CHYMOTRYPSIN ON LS* BY

Recent observations in our laboratories (1, 2) have demonstrated that a single molecular substance carries all of the serological activity of both the Land Ssoluble antigens of vaccinia. Craigie and Wishart, (3) who originally described these two antigens thought that they occurred in the form of a complex in nature, but, from their own observations (3) and from those of Parker (4), they were led to believe that the two serological substances could be dissociated into separate Land S-fractions under certain conditions (5). On the basis of our experience with degradation products of LS-antigen (1, 2) we formulated a different hypothesis to explain the apparent dissociation of the complex antigen; this dealt with the loss of precipitability of one part of the LS-molecule through degradation procedures which did not affect the other serologically active portion. Such an explanation would stand on a firm foundation if it were possible regularly to prepare a substance from pure LS-antigen which precipitated only with L-antibody. The purpose of this paper is to report the results of chemical analytical studies on pure LS-antigen which indicate the protein character of the molecule. In addition, a method for the enzymatic digestion of LS which results in a loss of the serological activity of the S-part of the molecule without destruction of the L-portion will be described.