Effect of temperature upon the circular dichroism of bradykinin.

Analysis of the effect of temperature on the circular dichroism spectrum of bradykinin has led to a more precise understanding of the solution conformation of the peptide. Circular dichroism and13C n.m.r. have been used in a complementary fashion to support the picture that bradykinin spends a maximum of about 20% of its time in a partially ordered conformation featuring a γ-turn with Pro7as the second residue. Since the γ-turn probability is insensitive to temperature, some other conformational effect dominated by the structure of water presumably produces the pronounced change in the circular dichroism spectrum with increasing temperature.