Conformational composition of neutral leucine. Matrix isolation infrared and ab initio study

Stepan G. Stepanian, Alexander Yu Ivanov, Ludwik Adamowicz

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Low-temperature matrix-isolation FTIR spectroscopy and ab initio calculations are employed to determine conformational composition of neutral leucine. The presence of three leucine conformers in the matrices is revealed. This is in agreement with the results of a detailed study of the potential energy surface of leucine which demonstrates that only five out of 105 possible conformers should have populations in the matrices larger than 2% and only three conformers, which are the ones detected in the experiment, should have populations larger than 10%. UV irradiation of the matrix samples are used to separate bands of the different conformers. We also show that the populations of the leucine conformers in the gas phase at 440 K are significantly different from the ones in matrices. The population of the lowest energy con- former in the gas phase being approximately 23% in the gas phase increases to over 64% in matrices.

Original languageEnglish (US)
Pages (from-to)20-29
Number of pages10
JournalChemical Physics
Volume423
DOIs
StatePublished - 2013

Keywords

  • Ab initio calculations
  • Conformer interconversion
  • Gibbs free energies
  • IR spectroscopy
  • Leucine
  • Matrix isolation

ASJC Scopus subject areas

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

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