Mechanisms of Photoisomerization of Polyenes in Confined Media: From Organic Glasses to Protein Binding Cavities

Authors

  • Robert S. H. Liu,

    Corresponding author
    1. Department of Chemistry, University of Hawaii, Honolulu, HI, USA
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    • Presented at the Photoisomerization Symposium of the PacifiChem Conference, Honolulu, Hawaii, USA, December 18, 2005.

  • Lan-Ying Yang,

    1. Department of Chemistry, University of Hawaii, Honolulu, HI, USA
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  • Jin Liu

    1. Department of Chemistry, Murray State University, Murray, KY, USA
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    • This invited paper is part of the Symposium-in-Print: Photobiology in Asia.


  • §Current address: Jin Liu, P.O. Box 3304, Alhambra, CA, USA.

*email: rshl@hawaii.edu (Robert S. H. Liu)

Abstract

Photochemical reactivities of model organic systems (stilbene and diphenylbutadiene) in organic glasses were first examined and compared with those in solution and in organized media. These observations were in turn compared with reactivities of polyene chromophores in protein binding cavities (specifically PYP, rhodopsin and bacteriorhodopsin). The obvious conclusion is that the preference for the most volume-conserving Hula-twist mechanism isomerization in organic glasses is because of the close interaction between the guest and the host molecules. In organized media (zeolites, crystals and protein binding cavities), the residual empty space coupled with any specific guest–host interactions that are characteristic of a given system, could lead to involvement of the more volume-demanding one-bond-flip (i.e. torsional relaxation) or bicycle-pedal or an extended HT process in photoisomerization.

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