Comparison of quantitative conformer analyses by nuclear magnetic resonance and Raman optical activity spectra for model dipeptides.
Interpretation of the Raman optical activity (ROA) of peptides is difficult because of molecular flexibility and interaction with the solvent. Typically, simulations and experiments are compared in terms of a qualitative agreement between the spectra. However, on a series of the Pro-Gly, Gly-Pro, Pro-Ala, and Ala-Pro dipeptides more precise conformer ratios could be obtained with the aid of the density functional computations and numerical decomposition of the spectral shapes. All observed transitions were assigned, and the computed transition frequencies were scaled accordingly. Then the populations predicted by the optical spectroscopy agreed within a few percent with an analysis of the spin-spin coupling constants based on the Karplus equations, which was confirmed also by a comparison of calculated and experimental NMR couplings. The results are supported by molecular dynamics simulations and related to the previous conformational studies of similar molecules.
Budesínský
Milos
M
Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo nám. 2, 16610, Prague 6, Czech Republic.
Danecek
Petr
P
Bednárová
Lucie
L
Kapitán
Josef
J
Baumruk
Vladimír
V
Bour
Petr
P
D003198:Computer Simulation; D004151:Dipeptides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008956:Models, Chemical; D008968:Molecular Conformation; D011789:Quantum Theory; D012015:Reference Standards; D015203:Reproducibility of Results; D013059:Spectrum Analysis, Raman / Q000379:methods* / Q000592:standards; D014732:Vibration
D004151:Dipeptides