- The gelation and melting processes in an isotropic solution of the helical polypeptide poly (y- benzyl-L-glutamate)[PBLG] were followed by small-angle x-ray scattering measurements. These suggest that above the gelation temperature PBLG exists as isolated helices. A sharp gelation transition is marked by an increase in the intensity scattered at low angles. Hysteresis of 20 C is observed between gelation and melting temperatures. The melting transition is gradual, suggesting that thinner units melt before thicker ones.