Raman Optical Activity of the Central Part of Hinge Peptide

Central cyclic part of the hinge peptide (a parallel dimer of the pentapeptide Boc-Cys-Pro-Pro-Cys-Pro-NHCH3 with two disulfide bonds) derived from the sequence of human IgG1 is a rather rigid structure having predominantly polyproline II helical conformation as shown by vibrational circular dichroism spectra. It exhibits significant Raman optical activity (ROA) signal due to vibrations associated with the disulfide bridges. We report positive ROA for the S-S stretching vibration at 510 cm-1 and for the C-S stretching vibration at 655 cm-1. These signals can provide means to assess the conformation of disulfide bridges in proteins, otherwise difficult to investigate.