A Little Light Work

Science's STKE  09 Aug 2005:
Vol. 2005, Issue 296, pp. tw294
DOI: 10.1126/stke.2962005tw294

Light-driven structural changes in proteins that are required for function are likely the result of photoexcitation processes redistributing charges. However, measuring changes in charge distribution on the time scale of the structural changes is challenging. Schenkl et al. have used Trp residues that are close to the retinal-binding pocket in bacteriorhodopsin to probe electric field changes. From the observed changes in Trp absorbance, they calculate that the retinal dipole moment increases during the first 200 femtoseconds after excitation. This change in charge distribution precedes, and likely drives, isomerization.

S. Schenkl, F. van Mourik, G. van der Zwan, S. Haacke, M. Chergui, Probing the ultrafast charge translocation of photoexcited retinal in bacteriorhodopsin. Science 309, 917-920 (2005). [Abstract] [Full Text]