Water and Alanine: From Puddles(32) to Ponds(49)

TitleWater and Alanine: From Puddles(32) to Ponds(49)
Publication TypeJournal Article
Year of Publication2009
AuthorsMullin JM, Gordon MS
Journal TitleJournal of Physical Chemistry B
Volume113
Pages14413-14420
Date Published10/29
ISBN Number1520-6106
Accession NumberISI:000270911100044
Keywordsapproximate formula, closed-shell molecules, crystal, energy, fragment potential method, glycine, intermolecular pauli repulsion, molecular-orbital methods, solvation, systems
Abstract

The solvation of alanine is investigated, with a focus on adding a sufficient number of discrete water molecules to determine the first solvation shell for both the nonionized (N) and zwitterionic (Z) forms to converge the enthalpy of solvation and the enthalpy difference for the two forms of alanine. Monte Carlo sampling was employed using the generalized effective fragment potential (EFP) method to determine the global minimum of both conformers, with the number of EFP water molecules ranging from 32-49. A subset of sampled geometries were optimized with second-order perturbation theory (MP2) using the 6-31++G(d,p) basis set. Single point energies were calculated at these geometries using the polarizable continuum model (PCM). The predicted 298.15 K enthalpy of solvation ranges for MP2/6-31++G(d,p) and MP2+PCM//MP2/6-31++G(d,p) are 10.0-13.2 kcal/mol and 10.1-12.6 kcal/mol, respectively.

URL<Go to ISI>://000270911100044
DOI10.1021/Jp904826v