09-17-04 18:29
No 531803
The Infrared and Ultraviolet Spectra of Individual Conformational Isomers of Biomolecules: Tryptamine
(Joel R. Carney and Timothy S. Zwier; J. Phys. Chem. (A) 2000, 104 (38), (8677-8688)) (Edit: year of publishment was added)
Abstract
Resonant ion-dip infrared (RIDIR) and UV-UV hole-burning spectroscopies are used to record the hydride stretch infrared spectra and S1S0 ultraviolet spectra of each of seven conformational isomers of tryptamine free from interference from one another. The different conformations of the ethylamine side chain produce unique S1S0 vibronic spectra, which can serve as the basis for RIDIR spectroscopy. The seven conformers possess unique spectral signatures in the alkyl CH stretch region of the infrared, which aid in the assignment of the observed transitions in the ultraviolet. Density functional theory (DFT) calculations of the structures, relative energies, and harmonic vibrational frequencies of nine low-energy minima are compared with the present and previous experimental data on tryptamine to assign the spectra of all seven conformers, all of which point the carbon out of the plane of the indole ring. The nine conformers consist of all combinations of the three minimum-energy amino group positions (anti, gauche toward the phenyl side, and gauche toward the pyrrole side of indole) and three amino group orientations (180, ±60) at each position. All three anti conformers are observed experimentally, whereas only the two lowest-energy of the three orientational conformers at each gauche position are observed. The dominant factor in determining the form of the CH stretch infrared spectrum is the orientation of the amino group, with the amino group position playing a secondary role. The frequencies of the S1S0 origin transitions, on the other hand, are most sensitive to the position of the amino group, whether it is anti, gauche phenyl, or gauche pyrrole. The prospects for using these methods more generally to characterize the conformations and energetics of flexible biomolecules are discussed.
indole_amine
(Hive Addict)
09-17-04 19:32
No 531818
Nice post, might I suggest you add the year of the journal so that TFSE can locate it when doing a search......java
J. Phys. Chem. A 104, 8677-8688, 2000
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