Basic and Combination Cross-Features in X- and Q-band HYSCORE of the 15N Labeled Bacteriochlorophyll a Cation Radical

AbstractChlorophylls are an essential class of cofactors found in all photosynthetic organisms. Upon absorbing a photon, the excited state energy of the chlorophyll can either be transferred to another acceptor molecule, or be used to drive electron transfer. When acting as the primary donor in the bacterial photosynthetic reaction center, light-induced charge separation results in the formation of a cationic bacteriochlorophyll dimer. The hyperfine interactions between the unpaired electron of the

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2P317 Quantum chemical study of the spin density distribution of the special pair cation radical in the bacterial photosynthetic reaction center(Photobiology-photosynthesis, and vision and photoreception,Oral Presentations)

Seibutsu Butsuri ◽

10.2142/biophys.47.s192_2 ◽

2007 ◽

Vol 47 (supplement) ◽

pp. S192

Author(s):

Hideki Yamasaki ◽

Yu Takano ◽

Haruki Nakamura

Keyword(s):

Density Distribution ◽

Spin Density ◽

Quantum Chemical ◽

Quantum Chemical Study ◽

Cation Radical ◽

Photosynthetic Reaction Center ◽

Chemical Study ◽

Special Pair ◽

Oral Presentations ◽

Bacterial Photosynthetic Reaction Center

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Switching sides—Reengineered primary charge separation in the bacterial photosynthetic reaction center

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1916119117 ◽

2019 ◽

Vol 117 (2) ◽

pp. 865-871 ◽

Cited By ~ 1

Author(s):

Philip D. Laible ◽

Deborah K. Hanson ◽

James C. Buhrmaster ◽

Gregory A. Tira ◽

Kaitlyn M. Faries ◽

...

Keyword(s):

Reaction Center ◽

Charge Separation ◽

Internal Conversion ◽

Photosynthetic Reaction Center ◽

Primary Electron ◽

Primary Electron Donor ◽

Primary Charge Separation ◽

Bacteriochlorophyll Dimer ◽

Initial Charge ◽

Bacterial Photosynthetic Reaction Center

We report 90% yield of electron transfer (ET) from the singlet excited state P* of the primary electron-donor P (a bacteriochlorophyll dimer) to the B-side bacteriopheophytin (HB) in the bacterial photosynthetic reaction center (RC). Starting from a platform Rhodobacter sphaeroides RC bearing several amino acid changes, an Arg in place of the native Leu at L185—positioned over one face of HB and only ∼4 Å from the 4 central nitrogens of the HB macrocycle—is the key additional mutation providing 90% yield of P+HB−. This all but matches the near-unity yield of A-side P+HA− charge separation in the native RC. The 90% yield of ET to HB derives from (minimally) 3 P* populations with distinct means of P* decay. In an ∼40% population, P* decays in ∼4 ps via a 2-step process involving a short-lived P+BB− intermediate, analogous to initial charge separation on the A side of wild-type RCs. In an ∼50% population, P* → P+HB− conversion takes place in ∼20 ps by a superexchange mechanism mediated by BB. An ∼10% population of P* decays in ∼150 ps largely by internal conversion. These results address the long-standing dichotomy of A- versus B-side initial charge separation in native RCs and have implications for the mechanism(s) and timescale of initial ET that are required to achieve a near-quantitative yield of unidirectional charge separation.

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