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

Autor: Juan Bertrán, Adrià Gil, Mariona Sodupe
Rok vydání: 2009
Předmět:
Zdroj: Journal of Computational Chemistry. 30:1771-1784
ISSN: 1096-987X
0192-8651
Popis: 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, epsilonL+* and epsilonD+* 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.
Databáze: OpenAIRE