Indoles at Interfaces: Calculations of Electrostatic Effects with Density Functional and Molecular Dynamics Methods

Thomas B. Woolf, Alan Grossfield, John G. Pearson

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Cation-π interactions have been suggested as a key determinant of aromatic amino acid behavior. These interactions can be modeled as an electrostatic quadrupole moment from the atoms of the ring interacting with the environment. The preference of aromatic amino acids for the interface of membrane bilayers has been suggested as an example of a cation-π effect. Recently, molecular dynamics simulations of indole and N-methylindole in an explicit POPC (palmitoyl oleoyl phosphatidylcholine) membrane bilayer have been performed, using the CHARMM potential function. The CHARMM potential does not explicitly contain cation-π interactions: The electrostatic model involves only point charges at the atomic centers. A proper interpretation of the molecular dynamics calculations requires an assessment of the accuracy of the electrostatic effects present in the CHARMM parameter set. The current study compares the electrostatic interaction energy from CHARMM with calculations using the density functional program deMon. The calculations were performed for the case of a single point charge approaching indole along the x, y, or z directions. Additional calculations used snapshots from the molecular dynamics trajectories of indole and N-methylindole to compare CHARMM and deMon electrostatic energies. The results suggest that much of the cation-π interactions for indole is effectively included within the CHARMM potential function.

Original languageEnglish (US)
Pages (from-to)197-206
Number of pages10
JournalInternational Journal of Quantum Chemistry
Issue number3
StatePublished - Jan 1 1999


  • Cation-π
  • Hydrophobicity scales
  • Indole
  • Interfacial effects
  • Membrane bilayers

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry


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