Thymosin alpha 11: a peptide related to thymosin alpha 1 isolated from calf thymosin fraction 5.

Two peptides related to thymosin alpha 1 have been isolated from preparations of calf thymosin fraction 5. One, lacking four amino acid residues at the COOH terminus, is designated des-(25-28)-thymosin alpha 1. The other, named thymosin alpha 11, contains seven additional amino acid residues at the COOH terminus. The sequence of this peptide is: AcSer-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu- Lys-Glu-Lys- Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-Gly-Arg-Glu-Ala-Pro-Ala-AsnOH. Thymosin alpha 11, in doses of less than 300 ng per mouse, protects susceptible inbred murine strains against opportunistic infections with Candida albicans. It is approximately equal to 30 times as potent as thymosin fraction 5 and approximately equal in potency to thymosin alpha 1.