Solvation model induced structural changes in peptides. A quantum chemical study on Ramachandran surfaces and conformers of alanine diamide using the polarizable continuum model

Authors

  • Ilona Hudáky,

    1. Biotechnology Research Group of the Hungarian Academy of Sciences, Department of Biochemistry, Eötvös Loránd University, Pázmány sétány 1/C, H-1117, Budapest, Hungary
    2. Department of Organic Chemistry, Eötvös Loránd University, P.O. Box 32, H–1518 Budapest, Hungary
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  • Péter Hudáky,

    1. Department of Organic Chemistry, Eötvös Loránd University, P.O. Box 32, H–1518 Budapest, Hungary
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  • András Perczel

    Corresponding author
    1. Department of Organic Chemistry, Eötvös Loránd University, P.O. Box 32, H–1518 Budapest, Hungary
    • Department of Organic Chemistry, Eötvös Loránd University, P.O. Box 32, H–1518 Budapest, Hungary
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Abstract

Potential energy surfaces of the model peptide HCO-L-Ala-NH2 were calculated using polarizable continuum model (PCM) for the description of aqueous solution at RHF/3-21G, RHF/6-31+G(d), and B3LYP/6-31+G(d) levels of theory. Energy minima were optimized at all three levels as well as at B3LYP/PCM/6-311++G(d,p) level of theory. Results were correlated to experimental data of protein structures retrieved from PDB SELECT. It is concluded that alanine residues of proteins are modeled better by PCM results than by gas-phase calculations on the alanine diamide model (frequently called alanine dipeptide model). The currently available version of the PCM model implemented in Gaussian 03 provides a reasonable alternative to anticipate solvation effects without the computational costs of introducing explicit solvent molecules into the model system. Frequencies calculated at RHF/PCM/6-31+G(d) and B3LYP/PCM/6-31+G(d) levels of theory show high correlation; thus, RHF results have their own merit. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1522–1531, 2004

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