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Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang

Mark Masthay

Experimental and theoretical evidence is presented which suggests that two distinct forms of light-adapted bacteriorhodopsin may exist. We propose that these two forms have characteristic photocycles with significantly different primary quantum yields. INDO-PSDCI molecular orbital procedures and semiempirical molecular dynamics simulations predict that one ground state geometry of bR undergoes photochemistry with a primary quantum yield, Φ1, of ~ 0.27, and that a second ground state geometry, with a slightly displaced counterion, yields Φ1 ~ 0.74. This theoretical model is supported by the observation that literature measurements of Φ1 tend to fall into one of two categories- those that observe …