Characterization of an Antibacterial Peptide from Calf Thymus.

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Abstract
The investigation was concerned with characterization of the basic calf thymus peptide of Bloom and coworkers (1947). The in vitro antibacterial potency was quite high, being in the range of antibiotic activity. Large acidic polymers blocked antibacterial action of the basic material. The peptide was more active at alkaline pH and more active against gram-positive bacteria. It acted against a pathogenic staphylo-coccus, several group A streptococci, Bacillus anthracis and Escherichia coli but exhibited little, if any, action against type II pneumococci, Salmonella typhosa or Vibrio comma. The product was very heat stable, non-dialyzable, water soluble and contained 6.4% nucleic acids and 0.8% carbohydrate. An amino acid analysis by the column chromatography revealed that it contained 35% lysine, 2% arginine and no histidine. The total amino acid composition tallied very closely with that of a calf thymus histone fraction reported by Crampton, et al, (1955).