Abstract
Since the helix-coil transition of synthetic polypeptides was first postulated, many methods have been developed to study this phenomenon. The chemistry of polypeptides in solution has been of particular interest, since it is useful in developing model systems for proteins. Both nonelectrolyte polypeptides and those with ionizable sidechains undergo a reversible transition between helix and random coil forms. This may be caused to occur, under certain conditions, by altering various parameters, such as, pH, solvent polarity, temperature, and ionic strength. | The helix-coil transition of poly(alpha)-L- glutamic acid, (PGA), has been studied extensively by many workers. P. Doty, et al. Observed the transition of this polymer in a dioxane-water solution, considering changes in intrinsic viscosity, specific rotation, and per cent ionization as functions of the pH of the solution. An abrupt change in both viscosity and optical rotation occurred over a range of per cent ionization values from 40 to 80 per cent, near pH 6. It was concluded that the essentially parallel changes in viscosity and optical rotation were indicative of the helix-coil transition.