Conformational studies of somatostatin and selected analogues by Raman spectroscopy

Laser Raman spectroscopy has been used to study the conformations of somatostatin and some selected analogues in aqueous solution. The results indicate that the CS-SC dihedral angles of somatostatin and of these analogues (except [Ala3,14]-SS, which has no disulfide bond) are within 20 degrees of +/- 85 degrees, and the SS-CC dihedral angles are predominantly in the range of 50 degrees-180 degrees. Furthermore, from the behavior of the amide I' and amide III bands, it appears that somatostatin adopts a beta-pleated sheet structure, whereas its analogues are less ordered (to varying degrees).