The role of water in the proton transfer reaction mechanism in tryptophan
- 19 August 2010
- journal article
- research article
- Published by Wiley in Journal of Computational Chemistry
- Vol. 31 (14), 2642-2649
- https://doi.org/10.1002/jcc.21559
Abstract
The role of water in the proton transfer mechanism between the carboxylic and the amino group in tryptophan was studied through the direct, intramolecular reaction in presence of a continuum and the single water molecule mediated, intermolecular reaction in vacuum and in presence of a continuum. The introduction of the continuum reduced the activation barriers for the proton transfer from the neutral form and stabilized the zwitterion in both cases. The reaction force and the reaction electronic flux along the intrinsic reaction coordinate allowed in combination with a Natural Bond Order Analysis a more detailed description of the influence of water on the reaction mechanism. Represented as a continuum model, water reduced the energy required for bond reorganization and did not alter the first part of the intermolecular reaction, characterized through the approximation of the water molecule to the functional groups of the amino acid and a polarization of the system. The absence of a water molecule in the intramolecular proton transfer with continuum changed the reaction coordinate to a reduction of the angle between the functional groups of the amino acid leaving the energy required for bond formation unaffected. Thus, the smaller activation barrier obtained in the direct intramolecular proton transfer with continuum model in comparison to the water mediated reaction, originates from the energetically more favorable angle reduction in comparison the approximation of a water molecule. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010This publication has 28 references indexed in Scilit:
- Solvent effect of aqueous media on properties of glycine: Significance of specific and bulk solvent effects, and geometry optimization in aqueous mediaInternational Journal of Quantum Chemistry, 2007
- Solvent effects on glycine II. Water‐assisted tautomerizationJournal of Computational Chemistry, 2004
- Effects of Microsolvation on the Structures and Reactions of Neutral and Zwitterion Alanine: Computational StudyThe Journal of Physical Chemistry B, 2003
- Solvent effects on glycine. I. A supermolecule modeling of tautomerization via intramolecular proton transferJournal of Computational Chemistry, 2003
- Theoretical study of solvent effect on intramolecular proton transfer of glycineJournal of Molecular Structure: THEOCHEM, 2000
- Intramolecular proton transfer of serine in aqueous solution. Mechanism and energeticsTheoretical Chemistry Accounts, 2000
- On the tautomerization process of glycine in aqueous solutionChemical Physics Letters, 2000
- Why is glycine a zwitterion in aqueous solution? A theoretical study of solvent stabilising factorsChemical Physics Letters, 1996
- On the Number of Water Molecules Necessary To Stabilize the Glycine ZwitterionJournal of the American Chemical Society, 1995
- Proof thatin density-functional theoryPhysical Review B, 1978