The potential of mean force surface for the alanine dipeptide in aqueous solution: a theoretical approach

B. Montgomery Pettitt, Martin Karplus

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Results of an application of integral equation theory to the determination of the intramolecular potential of mean force for the alanine dipeptide. N-methyl alanine acetamide, in aqueous solution are presented. The calculations are based on Ornstein-Zernike-like equations for polar systems with an intramolecular superposition approximation. The solvated free energy surface for the dipeptide as a function of the dihedral angles φ and ψ (Ramachandran plot) is determined and compared with the vaccum surface calculations. Conformations that are essentially forbidden in vaccum are found to be significant in aqueous solution. The solvent contributions to the free energy surface are decomposed into enthalpic and entropic terms. Possible applications and extensions of the method are outlined.

Original languageEnglish (US)
Pages (from-to)194-201
Number of pages8
JournalChemical Physics Letters
Issue number3
StatePublished - Nov 8 1985


ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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