poly peptids (pol-e-pep'tids)

A large group of compounds which have been prepared synthetically and some of which are found in the intermediate hydrolysis of proteins. They consist of the amino acids, combined in such a way that the carboxyl group (COOH) of one acid is united with the amido group (NH2) of another amido-acid. When two amido acids are combined in such a way we have a dipeptid, e. g., glycyl, glycin, alanyl-glycin. When three are combined we have a tri peptid, e. g., leucyl-glycyl alan in. And when more than three are combined, we have a poly peptid in the narrower sense of the word. There have been united in this way 18 amido-acid groups, with the formation of Fischer's oct a dec a peptid, a compound with a molecular weight of 1212, which compound has the highest molecular weight of any synthetical product of known constitution. Thus far eight of the dipeptids have been isolated as hydrolytic decomposition products of proteins.