Abstract
Ramachandran maps of neutral and ionized HCO-Gly-NH2 and HCO-Ala-NH2 peptide models have been built at the B3LYP/6-31++G(d, p) level of calculation. Direct optimizations using B3LYP and the recently developed MPWB1K functional have also been carried out, as well as single-point calculations at the CCSD(T) level of theory with the 6-311++G(2df, 2p) basis set. Results indicate that for both peptide models ionization can cause drastic changes in the shape of the PES in such a way that highly disallowed regions in neutral PES become low-energy regions in the radical cation surface. The structures localized in such regions, ε+•L and ε+•D are highly stabilized due to the formation of 2-centre-3-electron interactions between the two carbonyl oxygens. Inclusion of solvent effects by the conductor-like polarizable continuum model (CPCM) shows that the solute-solvent interaction energy plays an important role in determining the stability order. © 2008 Wiley Periodicals.
Original language | English |
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Pages (from-to) | 1771-1784 |
Journal | Journal of Computational Chemistry |
Volume | 30 |
Issue number | 12 |
DOIs | |
Publication status | Published - 1 Sep 2009 |
Keywords
- DFT
- Peptide
- Radical cation
- Ramachandran map