Femtosecond Infrared Spectroscopy of Bacteriorhodopsin Chromophore Isomerization

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Science  02 Aug 2002:
Vol. 297, Issue 5582, pp. 822-825
DOI: 10.1126/science.1072144

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The vibrational dynamics of the retinal chromophore all-trans–to–13-cis photoisomerization in bacteriorhodopsin has been studied with mid-infrared absorption spectroscopy at high time resolution (about 200 femtoseconds). After photoexcitation of light-adapted bacteriorhodopsin, the transient infrared absorption was probed in a broad spectral region, including vibrations with dominant C–C, C=C, and C=NH stretching mode amplitude. All photoproduct modes, especially those around 1190 reciprocal-centimeters that are indicative for a 13-cis configuration of the chromophore, rise with a time constant of ∼0.5 picosecond. The results presented give direct vibrational-spectroscopic evidence for the isomerization taking place within 0.5 picosecond, as has been suggested by previous optical femtosecond time-resolved experiments but questioned recently by picosecond time-resolved vibrational spectroscopy experiments.

  • * Present address: Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin, Germany.

  • To whom correspondence should be addressed. E-mail: diller{at}

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