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.
Structures of the eight lowest energy conformers of gaseous aspartic acid optimized at the level. The conformers are ordered according to their relative energies.
Simulated IR spectra (high frequency region) of four representative gaseous conformers.
The HOMO orbital of gaseous aspartic acid conformers.
Vertical ionization energies of canonical conformers of aspartic acid in gas phase and in solution using the CPCM.
The vibrational spectra of some zwitterionic conformers of aspartic acid in solution.
The vibrational spectra of two structurally similar conformers; conformer 8 in gas phase and conformer c1 in solution.
Representative zwitterionic and canonical aspartic acid conformers obtained by the discrete/SCRF model with two water molecules.
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.
Equilibrium distributions (%) of gaseous aspartic acid conformers at various temperatures. The electronic energies were obtained at the level.
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.
The relative energies of the aspartic acid conformers by the discrete/SCRF solution model with one and two water molecules.
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.
The energies of the zwitterionic Asp-water supermolecules and the canonical Asp-water supermolecules in gas phase.
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