- Peptide leucine arginine, a potent immunomodulatory peptide isolated and structurally characterized from the skin of the Northern Leopard frog, Rana pipiens. Salmon, A.L., Cross, L.J., Irvine, A.E., Lappin, T.R., Dathe, M., Krause, G., Canning, P., Thim, L., Beyermann, M., Rothemund, S., Bienert, M., Shaw, C. J. Biol. Chem. (2001)









