Raman studies on bradykinin and a cyclic bradykinin.

Laser Raman spectra of bradykinin in water, deuterium oxide, and the solid phase were recorded. From the spectra it was concluded that bradykinin conformation is comprised of ordered and unordered structure. The ordered structure appears to be some form of reverse turn. Furthermore, it seems that there is an enhancement of the turn structure in the solid phase. A cyclic cystine containing analog of bradykinin was also examined with Raman spectroscopy. The cyclic bradykinin analog gives a Raman spectrum very similar to that of the linear bradykinin and therefore must share similar conformational forms with bradykinin. The restrictive Cys-Cys disulfide in the cyclic bradykinin must serve to maintain a conformation acceptable to bradykinin receptors since the cyclic peptide exhibits biological activity.