Bacteriorhodopsin photoreaction: identification of a long-lived intermediate N (P, R350) at high pH and its M-like photoproduct

Citations Over TimeTop 10% of 1988 papers

Abstract

An alkaline suspension of light-adapted purple membrane exposed to continuous light showed a large absorption depletion at 580 nm and a small increase around 350 nm. We attribute this absorption change to an efficient photoconversion of bR570 into a photoproduct N (P,R350), which has a major absorption maximum between 550 and 560 nm but has lower absorbance than bR570. N was barely detectable at low pH, low ionic strength, and physiological temperature. However, when the thermal relaxation of N to bR570 was inhibited by increasing pH, increasing ionic strength, and decreasing temperature, its relaxation time could be as long as 10 s at room temperature. N is also photoactive; when it is present in significant concentrations, e.g., accumulated by background light, the flash-induced absorption changes of purple membrane suspensions were affected. Double-excitation experiments showed an M-like photoproduct of N,NM, with an absorption maximum near 410 nm and a much longer lifetime than M412. It may be in equilibrium with an L-like precursor NL. We suggest that N occurs after M412 in the photoreaction cycle and that its photoproduct NM decays into bR570. Thus, at high pH and high light intensity, the overall photoreaction of bR may be approximated by the two-photon cycle bR570----M412----N----(NL----NM)----bR570, whereas at neutral pH and low light intensity it can be described by the one-photon cycle bR570----M412----N----O640----bR570.(ABSTRACT TRUNCATED AT 250 WORDS)

Related Papers

• A GEOMETRIC MEAN IN THE FURUTA INEQUALITY(2002)
• Susquehanna Chorale Spring Concert "Roots and Wings"(2017)
• Коммуникaтивно- прaгмaтический aнaлиз дипломaтических бумaг (нa основе вербaльных нот)(2018)
• → ФОРМИРОВAНИЕ ГОТОВНОСТИ БУДУЩИХ ПЕДAГОГОВ К ОРГAНИЗAЦИИ РAБОТЫ ПО РAЗВИТИЮ ВAЛЕОЛОГИЧЕСКОЙ КУЛЬТУРЫ ШКОЛЬНИКОВ(2023)