Experimental and theoretical conformational studies on polypeptide models of collagen. Poly(Gly-Pro-Ile) and...

The synthetic polytripeptides poly(Gly-Pro-Ile) and poly(Gly-Ile-Pro) were studied both experimentally (mainly by circular dichroism spectroscopy) and theoretically by quantum mechanical methods. Poly(Gly-Ile-Pro) adopts a collagen-like structure under favourable conditions while the isomeric poly(Gly-Pro-Ile) does not. Theoretical studies emphasize severe intrastrand interactions which limit the main chain conformations in the case of poly(Gly-Ile-Pro). On the other hand, both the side cahin and the backbone in poly(Gly-Pro-Ile) can take up many different local conformations. Therefore, it seems that the conformational behaviour of synthetic polytripeptides can be at least partially explained in terms of local interactions.