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Rabbit antibodies against pneumococcus capsular polysaccharides of Types II, III, VI, VII, and XII were isolated from type-specific antisera by precipitation with homologous antigen and hydrolyzed with either subtilisin, chymotrypsin or trypsin. Purified antibodies were also hydrolyzed with papain; the two polypeptides with active antibody sites and the crystallizable polypeptide were separated, studied in the ultracentrifuge and hydrolyzed with either subtilisin or chymotrypsin. The resulting peptides were separated on filter paper by electrophoresis and chromatography. 1. The two polypeptides with antigen-combining activity, fractions I and II, each constituted about 25 per cent of the original antibody molecule; the crystallizable polypeptide did not combine with antigen, fraction III, and represented about 35 per cent of the original antibody molecule. About 10 to 15 per cent of the original antibody molecule was hydrolyzed by papain into about 35 peptides. 2. The peptide patterns obtained for hydrolyzates of fraction I were almost identical with those obtained for fraction II obtained from the same antibody and were quite different for those obtained for fraction III. 3. Many of the peptide spots in the patterns obtained with whole antibody hydrolysates contained at least two peptides derived from different parts of the antibody molecule. 4. Differences were observed in the peptide patterns for different antibodies that suggested the existence of differences in both primary and tertiary structures among these antibodies.

The chemical relations among Bence-Jones proteins, myeloma proteins, and normal gamma-globulins have been investigated by a variety of means. Starch gel electrophoresis in 8 M urea of reduced alkylated Bence-Jones proteins yielded patterns of bands corresponding to those of the light (L) polypeptide chains of the dissociated myeloma protein from the same patient. One instance in which this correspondence was found was chosen for extensive study. Chromatography on carboxymethylcellulose in 6 M urea was employed to isolate the light (L) polypeptide chains and heavy (H) polypeptide chains of the completely reduced and alkylated myeloma protein. Isolation of similarly treated Bence-Jones protein from the same patient corroborated the correspondence to the L chains of the myeloma protein. Amino acid analyses indicated that the compositions of the Bence-Jones protein and the L chains of the myeloma protein were identical. Moreover, the thermosolubility properties and spectrofluorometric behavior of the isolated L chains and Bence-Jones protein were similar. Ultracentrifugal analyses of the L chains of normal human 7S gamma-globulin showed that their molecular weight in 6 M urea was 20,000. In aqueous solution their molecular weight was 41,000, suggesting that they exist as dimers under these conditions. The L chains of normal human gamma-globulin were found to have reversible thermosolubility properties similar to those of Bence-Jones proteins. The H chains of normal human gamma-globulin did not share these properties. Using spectrofluorometric methods, characteristic molecular transitions were found upon heating Bence-Jones proteins and L chains. These transitions were indicated by an increase in the intensity of fluorescence at well defined temperatures as well as by reversible shifts in the wavelength of maximal emission. The findings suggest that Bence-Jones proteins are composed of L chains of the type found in normal and pathological gamma-globu]ins.

The blood and urine of mice and rats infected with Babesia rodhaini contain substances which stimulate the isolated guinea-pig ileum and rat duodenum. The amount of active material excreted increases as the infection increases. The active substances are stable to boiling with hydrochloric acid but not with alkali; they pass through a cellophane membrane and are soluble in hot ethanol. They are destroyed rapidly by papain and less rapidly by chymotrypsin, but are unaffected by trypsin or pepsin. Their action on smooth muscle is not affected by atropine, eserine, antihistamines, iproniazid, bretylium or by lysergic acid diethylamide. The active substances are probably peptides and there is evidence that the urine contains a mixture of peptides, some of which relax and some of which contract the rat duodenum. Similar active peptides appear in the urine of mice infected with Plasmodium berghei, Trypanosoma rhodesiense, Streptococcus pyogenes and Rift Valley fever virus.