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. 1993 Sep;65(3):1231–1234. doi: 10.1016/S0006-3495(93)81166-4

Thermal equilibration between the M and N intermediates in the photocycle of bacteriorhodopsin.

S Druckmann 1, M P Heyn 1, J K Lanyi 1, M Ottolenghi 1, L Zimanyi 1
PMCID: PMC1225842  PMID: 8241403

Abstract

The stages in the photocycle of bacteriorhodopsin (BR) involving the M and N intermediates are investigated using a double pulse excitation method. A first (cycling) pulse at 532 nm is followed, with an appropriate time delay, by a second pulse (337, 406, 446, or 470 nm) which induces the M-->BR back-photoreaction. After depletion by the second pulse a repopulation of M in the millisecond range is observed which is interpreted in terms of a thermal N-->M relaxation. It is thus concluded that a (thermal) M<-->N equilibrium accounts for the biphasic decay of M in the BR photocycle. Other models for this stage of the light-driven proton-pump are therefore unnecessary.

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Selected References

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