.alpha.-Helix and associated loop signatures in vibrational Raman optical activity spectra of proteins

Abstract

A comparison of the aqueous solution vibrational Raman optical activity (ROA) spectra of poly-L-lysine in random coil and α-helix conformations with those of bovine serum albumin and insulin, which are both rich in α-helix, is reported. Possible ROA signatures of α-helix include a broad positive band in the range ∼900-1000 cm -1 and a couplet, negative at low wavenumber and positive at high, centred at ∼1103 cm -1 , both features originating in backbone C α -C and C α -N stretch modes; a negative-positive couplet centred at ∼1275 cm -1 originating in backbone amide III C α H and NH deformations; and a positive band in the amide I region peaking at ∼1665 cm -1