The linear nonapeptide hormone bradykinin (Arg(1)-Pro(2)-pro(3)-Gly(4)-Phe(5)-Ser(6)-pro(7)-Phe(8) Arg(9)) is involved, either directly or indirectly, in a wide variety of physiological processes, particularly pain and hyperanalgesia. Additional evidence suggests that bradykinin also plays a major role in inflammatory response, asthma, sepsis, and symptoms associated with the rhinoviral infection. It has long been speculated that a beta-turn the C-terminus of bradykinin plays a major role in the biological activity of the neuropeptide. The beta-turn forming potential of bradykinin in three vastly different local chemical environments, DMSO, 9 : 1 dioxane/water, and in the presence of 7.4 mM lyse phosphatidylcholine micelles, was investigated using two-dimensional homonuclear nmr experiments coupled with simulated annealing calculations. The results of these investigations show that in all three systems residues 6-9 of the C-terminus adopt very similar beta-turn like structures. These results suggest that the beta-turn at the C-terminus of bradykinin is an important secondary structural feature for receptor recognition and binding. (C) 1994 John Wiley and Sons, Inc.