Influence of ionization on the conformational preferences of peptide models. Ramachandran surfaces of N-formyl-glycine amide and N-formyl-alanine amide radical cations

Adrià Gil, Mariona Sodupe, Juan Bertran

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3 Citations (Scopus)

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 languageEnglish
Pages (from-to)1771-1784
JournalJournal of Computational Chemistry
Volume30
Issue number12
DOIs
Publication statusPublished - 1 Sep 2009

Keywords

  • DFT
  • Peptide
  • Radical cation
  • Ramachandran map

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