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Proceedings Paper

Excited-state properties and physiological functions of biological polyenes: the triplet-excited region of retinoids and carotenoids
Author(s): Y. Koyama; Yumiko Mukai; Michitaka Kuki
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Paper Abstract

Both experimental and theoretical results which indicate the presence of the triplet-excited region in retinoids and carotenoids are reviewed. The triplet- excited region is defined as a region where changes in the bond order take place, upon triplet excitation, toward its inversion, i.e., a double bond becomes more signal bond-like and a single bond becomes more double bond-like. (1) It has a span of approximately six conjugated double bonds, (2) it is localized in the central part of a conjugated chain, and (3) it triggers `cis' to `trans' isomerization in the T1 state. The experimental and theoretical results include: (1) the T1 Raman spectra of all-trans-retinal and its homologues; (2) the T1-state isomerization of isomeric retinal; (3) the T1-state isomerization of isomeric (beta) -carotene; (4) the PPP-SD-CI calculations of the bond orders of the carbon-carbon bonds in a set of model polyenes; and (5) the normal-coordinate analysis of the T1 Raman lines of undeuterated and deuterated all-trans-retinal. Finally, (6) the biological implication of 'the triplet-excited region' is discussed in relation to the photo-protective function of a 15-cis carotenoid bound to the bacterial photoreaction center.

Paper Details

Date Published: 17 June 1993
PDF: 12 pages
Proc. SPIE 1921, Laser Spectroscopy of Biomolecules, (17 June 1993); doi: 10.1117/12.146119
Show Author Affiliations
Y. Koyama, Kwansei Gakuin Univ. (Japan)
Yumiko Mukai, Kwansei Gakuin Univ. (Japan)
Michitaka Kuki, Kwansei Gakuin Univ. (Japan)

Published in SPIE Proceedings Vol. 1921:
Laser Spectroscopy of Biomolecules
Jouko E. Korppi-Tommola, Editor(s)

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