5 α-Amino Acids In Water: A Review of VCD and ROA Spectra
121
proline forms were found in solution (and glass). the band broadenings, reproduced based on dynamic averaging found from the 2d potential energy surfaces,
revealed information about the extent of the proline ring motion and rotation of the
carbonyl group [206]. Comparison of the computed and experimental bandwidths
suggests that puckering is strongly correlated with carbonyl rotation. the study
indicated that the environment modulates the properties of the hydrophobic part of
the molecule indirectly by interacting with the ionic group. It was stressed that the
experimental spectra could not be explained and interpreted without dynamic and
solvent factors involved in the modelling.
As described for L-alanine, the role of internal motion in L-proline, ring puckering, rotation of the Co 2
−
group, and anharmonic factors on the RoA spectrum
were analysed by Daněček et al. [199]. many dFt functionals, careful exploration
of intensity tensors, degeneracy-corrected perturbation calculations, and large basis sets such as aug-cc-pvdZ and aug-cc-pvtZ (in conjunction with the B3PW91
functional) were exploited. unlike alanine, for proline, the anharmonic averaged
simulation provides a reasonable agreement with the experiment in the 1550–1205
cm
−1
region, yielding more realistic band shapes, frequencies, and RoA intensities.
Recently, Qiu et al. published an experimental and computational study on the
ph-dependency of L-proline RoA spectra in aqueous solution (Fig. 5.10) [207]. the
Fig. 5.9 Experimental ( top) and calculated ( bottom) Raman and RoA spectra of the L-proline
zwitterion ( left) and Nd 2 deuterated L-proline zwitterion ( right) in aqueous solutions. the calculations (L-enantiomers) were performed at the B3LYP/6-31 + + g**/CoSmo level for both conformers surrounded by three to eight water molecules; band positions are marked by the blue and
red lines for the A and B conformers, respectively, and the envelope was obtained as an average.
(Reproduced from Ref. [206] with kind permission of American Chemical Society)
121
proline forms were found in solution (and glass). the band broadenings, reproduced based on dynamic averaging found from the 2d potential energy surfaces,
revealed information about the extent of the proline ring motion and rotation of the
carbonyl group [206]. Comparison of the computed and experimental bandwidths
suggests that puckering is strongly correlated with carbonyl rotation. the study
indicated that the environment modulates the properties of the hydrophobic part of
the molecule indirectly by interacting with the ionic group. It was stressed that the
experimental spectra could not be explained and interpreted without dynamic and
solvent factors involved in the modelling.
As described for L-alanine, the role of internal motion in L-proline, ring puckering, rotation of the Co 2
−
group, and anharmonic factors on the RoA spectrum
were analysed by Daněček et al. [199]. many dFt functionals, careful exploration
of intensity tensors, degeneracy-corrected perturbation calculations, and large basis sets such as aug-cc-pvdZ and aug-cc-pvtZ (in conjunction with the B3PW91
functional) were exploited. unlike alanine, for proline, the anharmonic averaged
simulation provides a reasonable agreement with the experiment in the 1550–1205
cm
−1
region, yielding more realistic band shapes, frequencies, and RoA intensities.
Recently, Qiu et al. published an experimental and computational study on the
ph-dependency of L-proline RoA spectra in aqueous solution (Fig. 5.10) [207]. the
Fig. 5.9 Experimental ( top) and calculated ( bottom) Raman and RoA spectra of the L-proline
zwitterion ( left) and Nd 2 deuterated L-proline zwitterion ( right) in aqueous solutions. the calculations (L-enantiomers) were performed at the B3LYP/6-31 + + g**/CoSmo level for both conformers surrounded by three to eight water molecules; band positions are marked by the blue and
red lines for the A and B conformers, respectively, and the envelope was obtained as an average.
(Reproduced from Ref. [206] with kind permission of American Chemical Society)