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Quantum-classical description of the amide I vibrational spectrum of trialanine
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10.1063/1.2431803
/content/aip/journal/jcp/126/5/10.1063/1.2431803
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/5/10.1063/1.2431803

Figures

Image of FIG. 1.
FIG. 1.

Scheme and atom labeling of trialanine cation .

Image of FIG. 2.
FIG. 2.

maps of the mean (top) and the splitting (bottom) of the two amide I frequencies, as obtained for isolated glycine dipeptide (left), isolated trialanine (middle), and trialanine in (right).

Image of FIG. 3.
FIG. 3.

Distribution of the frequency splitting without (left) and with (right) the inclusion the solvent contribution, as obtained for the three conformational states of glycine dipeptide (top) and trialanine (bottom).

Image of FIG. 4.
FIG. 4.

Distribution of the amide I normal-mode frequencies obtained for the three conformational states of trialanine (a) in the gas phase and (b) in solution. Panel (c) shows the corresponding absorption bands calculated within the cumulant approximation.

Image of FIG. 5.
FIG. 5.

Solvent-induced frequency shifts (black solid line) and (red dashed line) of the amide I local modes of trialanine, plotted as a function of the distance between peptide and solvent atoms.

Image of FIG. 6.
FIG. 6.

(Left) Distribution of the solvent-induced amide I frequency shifts (black solid lines) and (red dashed lines), as obtained for the three conformational states of trialanine. (b) Radial distribution functions pertaining to the distance between (middle) the oxygen of the peptide unit and a hydrogen of water and (right) the hydrogen of the peptide unit and the oxygen of water , respectively.

Image of FIG. 7.
FIG. 7.

Correlation functions of the total transition dipole moment, shown for both amide I normal modes and the conformations , , and .

Image of FIG. 8.
FIG. 8.

Amide I absorption bands of trialanine obtained for the conformations , , and . Compared are results calculated directly from semiclassical line-shape theory [via Eq. (5), thick black lines], by invoking only the adiabatic approximation [via Eq. (8), thin red lines], and by invoking adiabatic and cumulant approximations [via Eq. (8), blue dashed lines].

Image of FIG. 9.
FIG. 9.

Comparison of experimental (Ref. 39, green dashed line) and calculated amide I absorption spectra of trialanine. The latter were obtained directly from semiclassical line-shape theory [via Eq. (5), thick black line] and by invoking adiabatic and cumulant approximations [via Eq. (8), thin red line].

Tables

Generic image for table
Table I.

Solvent-induced frequency shifts and of the amide I local modes of trialanine, comparing various electrostatic models (see text). Shown are the mean frequency shifts and , the full widths at half maximum and of the distributions, as well as the mean frequency gap , as obtained for the conformational states , , and . Units are .

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/content/aip/journal/jcp/126/5/10.1063/1.2431803
2007-02-06
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Quantum-classical description of the amide I vibrational spectrum of trialanine
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/5/10.1063/1.2431803
10.1063/1.2431803
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