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Ab initio studies of aspartic acid conformers in gas phase and in solution
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10.1063/1.2777161
/content/aip/journal/jcp/127/15/10.1063/1.2777161
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/15/10.1063/1.2777161

Figures

Image of FIG. 1.
FIG. 1.

Sketch of the molecular structure of aspartic acid with an illustration of rotating the six internal single-bond axes of aspartic acid (a) twofold, 0 and 180; (b) sixfold, 30, 90, 150, 210, 270, and 330; (c) threefold, , 60, and 180; (d) threefold: 60, 180, and 300; (e) threefold, 30, 90, 150, 210, 270, and 330; and (f) threefold, 0 and 180.

Image of FIG. 2.
FIG. 2.

Structures of the eight lowest energy conformers of gaseous aspartic acid optimized at the level. The conformers are ordered according to their relative energies.

Image of FIG. 3.
FIG. 3.

Simulated IR spectra (high frequency region) of four representative gaseous conformers.

Image of FIG. 4.
FIG. 4.

The HOMO orbital of gaseous aspartic acid conformers.

Image of FIG. 5.
FIG. 5.

Vertical ionization energies of canonical conformers of aspartic acid in gas phase and in solution using the CPCM.

Image of FIG. 6.
FIG. 6.

The vibrational spectra of some zwitterionic conformers of aspartic acid in solution.

Image of FIG. 7.
FIG. 7.

The vibrational spectra of two structurally similar conformers; conformer 8 in gas phase and conformer c1 in solution.

Image of FIG. 8.
FIG. 8.

Representative zwitterionic and canonical aspartic acid conformers obtained by the discrete/SCRF model with two water molecules.

Tables

Generic image for table
Table I.

Relative energies, relative zero-point vibrational energies, vertical ionization energies, rotational data, and dipole moments for the 15 lowest energy conformers of aspartic acid. Geometries optimized at the level and relative energies in kcal/mol at the (B3LYP), (MP2), and (CCSD) levels. Relative zero-point vibrational energies (ZPVE) in kcal/mol and rotational constants in GHz were calculated at the level and the dipole moment in Debye at the level. The vertical ionization energies (VIEs) in eV were computed at the level. includes ZPVE contributions to the total energies.

Generic image for table
Table II.

Equilibrium distributions (%) of gaseous aspartic acid conformers at various temperatures. The electronic energies were obtained at the level.

Generic image for table
Table III.

Relative energies, relative zero-point vibrational energies, vertical ionization energies, electron affinities, and conformational distribution for the canonical and zwitterionic conformers of aspartic acid in solution. Geometries optimized at the level and relative energies in kcal/mol at the (B3LYP) and (MP2) levels using the CPCM solution. The relative zero-point vibrational energies (ZPVEs) in kcal/mol and the vertical ionization energies (VIEs) and electron affinities (EAs) in eV were computed at the level using the CPCM solution. The conformational distributions (%) were computed with the MP2 energies and the B3LYP frequencies. Notice that only five canonical conformers with the lowest energies are listed, while numerous other high concentration canonical conformers are not shown here.

Generic image for table
Table IV.

The relative energies of the aspartic acid conformers by the discrete/SCRF solution model with one and two water molecules.

Generic image for table
Table V.

Relative energies and the equilibrium distribution of aspartic acid conformers in solution by the discrete/SCRF model. Relative energies of the supermolecules in kcal/mol were obtained at the (B3LYP) and (MP2) levels using the CPCM. The B3LYP and MP2 relative energies listed in this table included the ZPVE contributions at the level. The conformational distribution (%) at the standard condition was computed with the MP2 electronic energies and the B3LYP frequencies.

Generic image for table
Table VI.

The energies of the zwitterionic Asp-water supermolecules and the canonical Asp-water supermolecules in gas phase.

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/content/aip/journal/jcp/127/15/10.1063/1.2777161
2007-10-18
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Ab initio studies of aspartic acid conformers in gas phase and in solution
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/15/10.1063/1.2777161
10.1063/1.2777161
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