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1 March 2006 Photochemical Behavior and Na ,K -ATPase Sensitivity of Voltage-sensitive Styrylpyridinium Fluorescent Membrane Probes
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RH421 is a widely used voltage-sensitive fluorescent membrane probe. Its exposure to continuous illumination with 577 nm light from an Hg lamp leads, however, to an increase in its steady-state fluorescence level when bound to lipid membranes. The increase occurs on the second time scale at typical light intensities and was found to be due to a single-photon excited-state isomerization. Modifications to the dye structure are, therefore, necessary to increase photochemical stability and allow wider application of such dyes in kinetic studies of ion-transporting membrane proteins. The related probe ANNINE 5, which has a rigid polycyclic structure, shows no observable photochemical reaction when bound to DMPC vesicles on irradiation with 436 nm light. The voltage sensitivity of ANNINE 5 was tested with the use of Na ,K -ATPase membrane fragments. As long as ANNINE 5 is excited on the far red edge of its visible absorption band, it shows a similar sensitivity to RH421 in detecting charge-translocating reactions triggered by ATP phosphorylation. Unfortunately the wavelengths necessary for ANNINE 5 excitation are in a region where the Hg lamps routinely used in stopped-flow apparatus have no significant lines available for excitation.

Steve Amoroso, Vanessa V. Agon, Thomas Starke-Peterkovic, Malcolm D. McLeod, Hans-Jürgen Apell, Pierre Sebban, and Ronald J. Clarke "Photochemical Behavior and Na ,K -ATPase Sensitivity of Voltage-sensitive Styrylpyridinium Fluorescent Membrane Probes," Photochemistry and Photobiology 82(2), 495-502, (1 March 2006).
Received: 7 June 2005; Accepted: 1 October 2005; Published: 1 March 2006

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