Campus Units
Chemistry
Document Type
Article
Publication Version
Published Version
Publication Date
6-2009
Journal or Book Title
Journal of Physical Chemistry B
Volume
113
Issue
25
First Page
8657
Last Page
8669
DOI
10.1021/jp901459y
Abstract
An ab initio study of the addition of successive water molecules to the amino acid l-alanine in both the nonionized (N) and zwitterionic (Z) forms are presented. The main focus is the number of waters needed to stabilize the Z form and how the solvent affects conformational preference. The solvent is modeled by ab initio electronic structure theory, the EFP (effective fragment potential) model, and the isotropic dielectric PCM (polarizable continuum method) bulk solvation techniques. The EFP discrete solvation model is used with a Monte Carlo algorithm to sample the configuration space to find the global minimum. Bridging structures are predicted to be the lowest energy Z minima after 3−5 discrete waters are included in the calculations, depending on the level of theory. Second-order perturbation theory and PCM stabilize the Z structures by ∼3−6 and 7 kcal/mol, respectively, relative to the N global minimum through the addition of up to 8 waters. Subsequently, the contributions of each are ∼1 kcal/mol relative to the N global minimum. The presence of 32 waters appears to be close to converging the N−Z enthalpy difference, ΔHN−Z.
Copyright Owner
American Chemical Society
Copyright Date
2009
Language
en
File Format
application/pdf
Recommended Citation
Mullin, Jonathan M. and Gordon, Mark S., "Alanine: Then There Was Water" (2009). Chemistry Publications. 514.
https://lib.dr.iastate.edu/chem_pubs/514
Comments
Reprinted (adapted) with permission from Journal of Physical Chemistry B 113 (2009): 8657, doi:10.1021/jp901459y. Copyright 2009 American Chemical Society.