A theoretical study of the structures of (Gly-Pro-Leu)n and (Gly-Leu-Pro)n.

Theoretical conformation studies have been carried out for the polytripeptides (Gly-Pro-Leu)n and (Gly-Leu-Pro)n and the Fourier transforms of the structures have been calculated. X-ray powder patterns of these polymers had indicated that both these polymers take up coiled-coil triple-helical structures, but in the case of (Gly-Pro-Leu)n it was not clear whether the triple helix is formed by three parallel polypeptide chains or by a single chain folding back on itself (Scatturin et al 1975). Our studies show that both the polytripeptides can take up stereochemically satisfactory triple-helical structures with three parallel chains. There is also very good agreement between the calculated intensity distribution and that of the observed X-ray pattern, in each case.