Mode recognition in UV resonance Raman spectra of imidazole: histidine monitoring in proteins.
The imidazole side-chains of histidine residues perform key roles in proteins, and spectroscopic markers are of great interest. The imidazole Raman spectrum is subject to resonance enhancement at UV wavelengths, and a number of UVRR markers of structure have been investigated. We report a systematic experimental and computational study of imidazole UVRR spectra, which elucidates the band pattern, and the effects of protonation and deprotonation, of H/D exchange, of metal complexation, and of addition of a methyl substituent, modeling histidine itself. A consistent assignment scheme is proposed, which permits tracking of the bands through these chemical variations. The intensities are dominated by normal mode contributions from stretching of the strongest ring bonds, C(2)N and C(4)C(5), consistent with enhancement via resonance with a dominant imidazole π-π* transition.
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Gurusamy
G
Balakrishnan
Andrzej A
AA
Jarzecki
Qiang
Q
Wu
Pawel M
PM
Kozlowski
Daojing
D
Wang
Thomas G
TG
Spiro
D001665:Binding Sites; D056831:Coordination Complexes / Q000737:chemistry; D006639:Histidine / Q000032:analysis*; D007093:Imidazoles / Q000032:analysis*; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013059:Spectrum Analysis, Raman / Q000379:methods*
D056831:Coordination Complexes; D007093:Imidazoles; D008670:Metals; D011506:Proteins; D011522:Protons; D006639:Histidine; C029899:imidazole