The Antigenic Structure of Hemolytic Streptococci of Lancefield Group A

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Abstract
Summary: Electrophoretic examination of the M-substance confirmed the fact that the nucleic acid present was free and that there was very little other contamination of the type-specific protein. Determinations of the mobility of the chemically purified type-specific M-protein at various pHs indicated that its isoelectric point is about pH 5.4. The mobility of the NPA-protein at pH 6.0 and 8.0 has been found to be twice as great as that of the M-protein and permits the recognition of each in mixtures. Nucleic acid was found to be the principal contaminant of NPA preparations. The nucleic acids encountered have high mobilities and the values determined in mixtures of protein and nucleic acid, such as the M-substance and NPA, were similar to those for purified streptotoccal nucleic acids. The data obtained for streptococcal nucleic acid are discussed in relation to the mobilities of yeast and thymus nucleic acid. It was concluded that the streptococcal capsular polysaccharide was not present in any of the streptococcal fractions studied since no component was seen with the mobilities to be expected from a study of the similar vitreous-humor polysaccharide. The mobility of this polysaccharide was high and the same at both pH 6.0 and 8.0. The group-specific polysaccharide, observed in one preparation of other streptococcal fractions, on the basis of this and more extensive observations with the purified polysaccharide, had little or no mobility.

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