NEXAFS spectroscopy of homopolypeptides at all relevant absorption edges: polyisoleucine, polytyrosine, and polyhistidine.
Carefully calibrated high-resolution low-noise near-edge X-ray absorption fine structure spectra of three homopolypetides, viz., polyisoleucine, polytyrosine, and polyhistidine at the C, N, and O K-edges, are compared with the respective spectra of parent amino acids and glycine-derived cyclic dipeptide, 2,5-diketopiperazine. An assignment of the spectral features related to the nitrogen and oxygen atoms constituting the peptide bond is suggested on the basis of a comparative analysis of the experimental spectra as well as theoretical calculations for 2,5-diketopiperazine within the real-space multiple-scattering formalism. A splitting of the pi*-feature in the N K-edge spectra is identified, which is probably sensitive to the dominant conformation type of the peptide molecule (i.e., alpha-helix vs beta-sheet).
Angewandte Physikalische Chemie, University of Heidelberg, INF 253, 69120 Heidelberg, Germany. zubavichus@urz.uni-heidelberg.de
Yan
Y
Zubavichus
Andrey
A
Shaporenko
Michael
M
Grunze
Michael
M
Zharnikov
D000042:Absorption; D006571:Heterocyclic Compounds / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D013057:Spectrum Analysis; D014965:X-Rays
D006571:Heterocyclic Compounds; D010455:Peptides; C033223:polyhistidine; C017663:polytyrosine; C043801:polyisoleucine; D006639:Histidine; D009584:Nitrogen; D010100:Oxygen