Human sweat on a fingertip.

Frogs aren't the only ones secreting proteins with antibiotic properties Magainin is a 23-residue protein secreted in the skin of the African clawed frog Xenopus Leavis . These peptides bind to membranes in their helical form, but have a stable coil form as well. The thermodynamics of the helix-coil transition in this protein has recently been studied [T. Wieprecht, O. Apostolov, M. Beyermann, J. Seelig, J.Mol.Bio. 294 (1999) 785-794]. Of course, exotic frogs are not the only species to produce antibacterial substances. Organisms ranging from Drosphila to humans synthesize various proteins with antibiotic properties. Dermcidin is a 47-residue polypeptide secreted in human sweat that behaves as an antbacterial agent. Cathelicidins are found throughout human tissues, and were first identified by their ability to kill off type A strep.

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