title: Quantum Mechanics Approach to Hydration Energies and Structures of Alanine and Dialanine.
abstract: A systematic approach to the phenomena related to hydration of biomolecules is reported at the state of the art of electronic-structure methods. Large-scale CCSD(T), MP4-SDQ, MP2, and DFT(M06-2X) calculations for some hydrated complexes of alanine and dialanine (Ala⋅13 H2O, Ala2H+⋅18 H2O, and Ala2⋅18 H2O) are compared with experimental data and other elaborate modeling to assess the reliability of a simple bottom-up approach. The inclusion of a minimal number of water molecules for microhydration of the polar groups together with the polarizable continuum model is sufficient to reproduce the relative bulk thermodynamic functions of the considered biomolecules. These quantities depend on the adopted electronic-structure method, which should be chosen with great care. Nevertheless, the computationally feasible MP2 and M06-2X functionals with the aug-cc-pVTZ basis set satisfactorily reproduce values derived by high-level CCSD(T) and MP4-SDQ methods, and thus they are suitable for future developments of more elaborate and hence more biochemically significant peptides.
authors.affiliation: Dipartimento di Scienze del Farmaco, Università di Catania, Viale A. Doria 6, Catania, 95125, Italy.
authors.forename: Giuseppe
authors.identifier: http://orcid.org/0000-0002-8358-0885
authors.initials: G
authors.lastname: Lanza
authors.affiliation: Dipartimento di Scienze del Farmaco, Università di Catania, Viale A. Doria 6, Catania, 95125, Italy.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Chiacchio
mesh_terms: D000409:Alanine / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D004151:Dipeptides; D014867:Water; C002956:alanylalanine; D000409:Alanine
keywords: ab initio calculations; amino acids; density functional calculations; hydrates; hydrogen bonds