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Conformational preferences of jet-cooled melatonin: Probing trans- and cis-amide regions of the potential energy surface

Florio, GM and Christie, RA and Jordan, KD and Zwier, TS (2002) Conformational preferences of jet-cooled melatonin: Probing trans- and cis-amide regions of the potential energy surface. Journal of the American Chemical Society, 124 (34). 10236 - 10247. ISSN 0002-7863

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The hormone melatonin (N-acetyl-5-methoxytryptamine) is an indole derivative with a flexible peptide-like side chain attached at the C3 position. Using a combination of two-color resonant two-photon ionization (2C-R2PI), laser-induced fluorescence excitation (LIF), resonant ion-dip infrared spectroscopy (RIDIRS), fluorescence-dip infrared spectroscopy (FDIRS), and UV-UV hole-burning spectroscopy, the conformational preferences of melatonin in a molecular beam have been determined. Three major transamide conformers and two minor cis-amide conformers have been identified in the R2PI spectrum and characterized with RIDIRS and FDIRS. Structural assignments are made using the infrared spectra in concert with density functional theory and localized MP2 calculations. Observation of cis-amide melatonin conformers in the molecular beam, despite the large energy gap (∼3 kcal/mol) between trans- and cis-amides, is striking because there are at least nine lower-energy trans-amide minima that are not detected. The implications of this observation for cooling and trapping conformational population in a supersonic expansion are discussed.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Florio, GM
Christie, RA
Jordan, KDjordan@pitt.eduJORDAN
Zwier, TS
Date: 28 August 2002
Date Type: Publication
Journal or Publication Title: Journal of the American Chemical Society
Volume: 124
Number: 34
Page Range: 10236 - 10247
DOI or Unique Handle: 10.1021/ja0265916
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0002-7863
PubMed ID: 12188688
Date Deposited: 01 Apr 2013 20:31
Last Modified: 02 Feb 2019 15:56


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