Journal article
Gas-Phase Photochemistry of the Photoactive Yellow Protein Chromophore trans-p-Coumaric Acid
Journal of the American Chemical Society, Vol.124(21), pp.6194-6201
05/29/2002
DOI: 10.1021/ja017505p
PMID: 12022854
Abstract
The photoisomerization of trans-p-coumaric acid (trans-CA) triggers a photocycle in photoactive yellow protein that ultimately mediates a phototactic response to blue light in certain purple bacteria. We have used fluorescence excitation and dispersed emission methods in a supersonic jet to investigate the nature of the electronic excited states involved in the initial photoexcitation and subsequent photoisomerization of trans-CA. We observed three distinct regions in the fluorescence excitation spectrum of trans-CA. Region I is characterized by sharp features that upon excitation exhibit trans-CA S(1) emission. In region II, features increase in width and decrease in intensity with increasing excitation energy. Upon excitation, we observed dual emission from the S(1) state of trans-CA and what may be the S(1) state of cis-CA. The onset of dual emission corresponds to an isomerization barrier of about 3.4 kcal/mol. Finally, the extremely broad absorption feature in region III is excitation to the S(2) electronic excited state and excitation results in trans-CA S(1) emission. Furthermore, we collected CA from the molecular beam after laser excitation in each of the three regions as further evidence of the photoisomerization process. The relative amounts of trans- and cis-CA in the collected molecules were measured with high-pressure liquid chromatography. Although trans-CA was excited in all three regions, a significant cis-CA peak appeared only in region II, though a small cis peak was observed in region III.
Details
- Title: Subtitle
- Gas-Phase Photochemistry of the Photoactive Yellow Protein Chromophore trans-p-Coumaric Acid
- Creators
- Wendy L RYAN - Contribution from the Departments of Chemistry and Biochemistry and Molecular Biology andthe James Franck Institute, University of Chicago, Chicago, Illinois 60637David J GORDON - Contribution from the Departments of Chemistry and Biochemistry and Molecular Biology andthe James Franck Institute, University of Chicago, Chicago, Illinois 60637Donald H LEVY - Contribution from the Departments of Chemistry and Biochemistry and Molecular Biology andthe James Franck Institute, University of Chicago, Chicago, Illinois 60637
- Resource Type
- Journal article
- Publication Details
- Journal of the American Chemical Society, Vol.124(21), pp.6194-6201
- Publisher
- American Chemical Society
- DOI
- 10.1021/ja017505p
- PMID
- 12022854
- ISSN
- 0002-7863
- eISSN
- 1520-5126
- Language
- English
- Date published
- 05/29/2002
- Academic Unit
- Stead Family Department of Pediatrics; Hematology/Oncology
- Record Identifier
- 9984093310402771
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