Empirical solvent correction for multiple amide group vibrational modes.
Previously proposed solvent correction to the amide I peptide vibration was extended so that it can be applied to a general solvated chromophore. The combined molecular and quantum mechanics (MMQM) method is based on a linear dependence of harmonic force field and intensity tensor components of the solute on solvent electrostatic field. For N-methylacetamide, realistic solvent frequency and intensity changes as well as inhomogeneous band widths were obtained for amide A, I, II , and III modes. A rather anomalous basis set size dependence was observed for the amide A and I vibrations, when bigger basis lead to narrowing of spectral bands and lesser molecular sensibility to the environment. For a model alpha-helical peptide, a W-shape of the vibrational circular dichroism signal observed in deuterated solvent for the amide I band was reproduced correctly, unlike with previous vacuum models.
Bour
Petr
P
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Praha 6, Czech Republic. bour@uochb.cas.cz
Michalík
David
D
Kapitán
Josef
J