Issue 29, 2015

On the interaction between the imidazolium cation and aromatic amino acids. A computational study

Abstract

Complexes formed by the imidazolium cation and the aromatic amino acids, phenylalanine, tyrosine, tryptophan, and histidine have been studied by using computational methods. Complexation energies estimated at the MP2.X level amount to −123.3, −124.6, −131.5 and −145.5 kJ mol−1 for Phe, Tyr, Trp and His, respectively. The results obtained for Phe, Tyr and Trp complexes are similar, with the most stable minima corresponding to structures with the imidazolium cation stacked over the rings. The cation forms hydrogen bonds with the amino acid while establishing cation⋯π contacts with the aromatic rings. Extended structures with the amino acids in zwitterionic form are almost equally stable, though. The interaction is controlled by electrostatics and induction, though the preference for the stacked minima is due to larger contributions from induction and dispersion despite the energy cost of folding the amino acid. His complexes exhibit a totally different behaviour, and no structures displaying cation⋯π interactions are found among the most stable minima. Most favourable complexes of His show the cation hydrogen bonded to the amino acid in extended zwitterionic form. Overall, Phe, Tyr and Trp complexes can show parallel structures in competition with similarly stable zwitterionic ones, while His only shows zwitterionic minima, with a stability even larger than any of the other aromatic amino acids, though lacking participation of the π cloud in the interaction.

Graphical abstract: On the interaction between the imidazolium cation and aromatic amino acids. A computational study

Supplementary files

Article information

Article type
Paper
Submitted
03 Jun 2015
Accepted
16 Jun 2015
First published
16 Jun 2015

Org. Biomol. Chem., 2015,13, 7961-7972

On the interaction between the imidazolium cation and aromatic amino acids. A computational study

A. A. Rodríguez-Sanz, E. M. Cabaleiro-Lago and J. Rodríguez-Otero, Org. Biomol. Chem., 2015, 13, 7961 DOI: 10.1039/C5OB01108F

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