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Published byApril Hutchinson Modified over 9 years ago
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Ultrafast Short-range Electron Transfer Dynamics in Biology
Ting-Fang He Dr. Dongping Zhong Programs of Ohio State Biochemistry, Biophysics, and Chemical Physics, and Departments of Physics, Chemistry, and Biochemistry, The Ohio State University, Columbus, Ohio 43210
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Chemistry Physics Biology ELECTRON TRANSFER Signal transduction
Phosphorylation Dephosphorylation Proton translocation Cell respiratory chain Energy conversion processes Oxidation; reduction Organic synthesis Solid-state physics Surface physics Biology
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Biology Photosynthesis light Phototropism DNA repair , etc. Electron
Transfer DNA repair , etc. Current Opinion in Chemical Biology 2007, 11:174–181 DNA repair Cold Spring Harbor Laboratory Press: Cold Spring Harbor, NY (2007).
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Ultrafast Electron Transfer Dynamics
Flavodoxin (D. Vulgaris) e- e- light kET A* D A- D+ The roles of all nuclear motions to ET have been well studied theoretically and experimentally under simple chemical molecules in solution. In addition to the energetics, how much input of solvent motion plus solute motion are weighted? How does it play with the increase of tunneling distances? How does enzyme turn off (slow down) the backward dynamics, increase the competence of forward ET and reach the efficiency of downstream function? At short range, how does protein steer electron transfer dynamics by coupling with the active-site motions ? hν Redox bacterial proteins. Act as an electron shuttle. Sulfite-reducing system; Nitrogen fixation. kBACK ET A D
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fs ps ns µs Nuclear motion in protein
Upper-limit electron transfer dynamics at the tunneling distances in protein 20 Ǻ 10 Ǻ 15 Ǻ 5 Ǻ Close contact Nuclear motion in protein J. Phys. Chem. B, Vol. 108, No. 46, 2004 Protein nuclear motion includes vibrational degree of freedom at short times and solvation at longer times.
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Results τBACK ET ~ 1.5 ps τBACK ET ~ 1.5 ps τET τET ~ 0.4 ps τBACK ET
λ probe 580 nm λ flu 530 nm τET ~ 0.4 ps Results Flavodoxin Y98F kET e- kBACK ET τBACK ET ~ 1.5 ps λ probe 490 nm τET FMN* Trp FMN- Trp+ 400 nm τBACK ET FMN Trp
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Electron Transfer Coordinate
Flavodoxin Y98F λ probe 540 nm λ probe 510 nm λ probe 518 nm λ probe 525 nm λ probe 560 nm time/ ps Results 1.5 ps 4.5 ps 400 nm Electron Transfer Coordinate ultrafast forward electron transfer Trp FMN* Solvation plus back electron transfer Trp+ FMN- 400 nm Trp FMN
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Results kET kBACK ET Flavodoxin W60F time/ ps λ probe 540 nm
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Results kET kBACK ET Flavodoxin wild type time/ ps λ probe 560 nm
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Conclusion How universal in regulating the biological function?
(a) Under the oxidized flavodoxin, the forward electron transfer dynamics from the van der Waals contact aromatic amino acids to the excited flavin is determined faster than 0.5 ps. (b) The back electron transfer turns out being more than two times slower than its forward, ~1.5 ps. (c) The recombination process is found at the hot ground state before the redox molecules and the protein solvents relax vibrationally to the equilibrated configurations. (d) The subsequent vibrational relaxation (cooling) is determined ~5 ps in the active-site pocket. (e) The study indicates that, for the highly exergonic back electron transfer (the inverted region), at this short range, there appears a hot channel at the vibrational excited electronic ground state to boost the return dynamics. How universal in regulating the biological function?
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Acknowledgements Advisor Professor Coworkers Group Members Funding
Dr. Dongping Zhong Professor Richard P. Swenson Coworkers Lijuan Wang Dr. Lijun Guo Dr. Chaitanya Saxena Ya-Ting Kao Group Members Qing Ding Dr. Xunmin Guo Ali Hassanali Dr. Jiang Li Tangping Li Zheyun Liu Jingwei Lu Justin Link Oseoghaghare Okobiah Weihong Qiu Jeff Stevens Chuang Tan Yi Yang Chen Zang Luyuan Zhang Funding the National Institutes of Health the Packard Foundation Fellowship
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