Electronic and Vibrational Optical Activity of Several Peptides Related to Neurohypophyseal Hormones: Disulfide Group Conformation

ABSTRACT: Electronic and vibrational optical activity of the set ofneurohypophyseal hormones and their analogs wasinvestigated to clarify the S S bond solutionconformation. The selected compounds include oxytocin(I), lysine vasopressin (II), arginine vasopressin (III), andtheir analogs (IV–IX), differing widely in theirpharmacological properties. We have extended thealready known electronic circular dichroism data by newinformation provided by vibrational circular dichroism(VCD) and Raman optical activity (ROA). The use ofVCD brought additional details on three-dimensionalstructure of the chain reversal in the ring moiety and onits left handedness. Furthermore, Raman scattering andROA allowed us to deduce the sense of the disulfide bondtorsion. # 2012 Wiley Periodicals, Inc. Biopolymers 97:923–932, 2012.Keywords: neurohypophyseal hormones; disulfide bridge;chiroptical spectroscopy; circular dichroism; Ramanoptical activity; vibrational circular dichroism; oxytocin;vasopressin; analogs; conformation