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Title: Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation

Authors:
; ; ; ; ; ; ; ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Biological Electron Transfer and Catalysis (BETCy)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1388992
DOE Contract Number:
SC0012518
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Biological Chemistry; Journal Volume: 292; Journal Issue: 34; Related Information: BETCy partners with Montana State University (lead); Arizona State University; National Renewable Energy Laboratory; University of Georgia; University of Kentucky; University of Washington; Utah State University
Country of Publication:
United States
Language:
English
Subject:
solar (fuels), biofuels (including algae and biomass), bio-inspired, hydrogen and fuel cells

Citation Formats

Hoben, John P., Lubner, Carolyn E., Ratzloff, Michael W., Schut, Gerrit J., Nguyen, Diep M. N., Hempel, Karl W., Adams, Michael W. W., King, Paul W., and Miller, Anne-Frances. Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation. United States: N. p., 2017. Web. doi:10.1074/jbc.M117.794214.
Hoben, John P., Lubner, Carolyn E., Ratzloff, Michael W., Schut, Gerrit J., Nguyen, Diep M. N., Hempel, Karl W., Adams, Michael W. W., King, Paul W., & Miller, Anne-Frances. Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation. United States. doi:10.1074/jbc.M117.794214.
Hoben, John P., Lubner, Carolyn E., Ratzloff, Michael W., Schut, Gerrit J., Nguyen, Diep M. N., Hempel, Karl W., Adams, Michael W. W., King, Paul W., and Miller, Anne-Frances. Wed . "Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation". United States. doi:10.1074/jbc.M117.794214.
@article{osti_1388992,
title = {Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation},
author = {Hoben, John P. and Lubner, Carolyn E. and Ratzloff, Michael W. and Schut, Gerrit J. and Nguyen, Diep M. N. and Hempel, Karl W. and Adams, Michael W. W. and King, Paul W. and Miller, Anne-Frances},
abstractNote = {},
doi = {10.1074/jbc.M117.794214},
journal = {Journal of Biological Chemistry},
number = 34,
volume = 292,
place = {United States},
year = {Wed Jun 14 00:00:00 EDT 2017},
month = {Wed Jun 14 00:00:00 EDT 2017}
}
  • Flavin-based electron transfer bifurcation is emerging as a fundamental and powerful mechanism for conservation and deployment of electrochemical energy in enzymatic systems. In this process, a pair of electrons is acquired at intermediate reduction potential (i.e. intermediate reducing power) and each electron is passed to a different acceptor, one with lower and the other with higher reducing power, leading to 'bifurcation'. It is believed that a strongly reducing semiquinone species is essential for this process, and it is expected that this species should be kinetically short-lived. We now demonstrate that presence of a short-lived anionic flavin semiquinone (ASQ) is notmore » sufficient to infer existence of bifurcating activity, although such a species may be necessary for the process. We have used transient absorption spectroscopy to compare the rates and mechanisms of decay of ASQ generated photochemically in bifurcating NADH-dependent ferredoxin-NADP + oxidoreductase and the non-bifurcating flavoproteins nitroreductase, NADH oxidase and flavodoxin. We found that different mechanisms dominate ASQ decay in the different protein environments, producing lifetimes ranging over two orders of magnitude. Capacity for electron transfer among redox cofactors vs. charge recombination with nearby donors can explain the range of ASQ lifetimes we observe. In conclusion, our results support a model wherein efficient electron propagation can explain the short lifetime of the ASQ of bifurcating NADH-dependent ferredoxin-NADP + oxidoreductase I, and can be an indication of capacity for electron bifurcation.« less
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  • Online isotopes separators (ISOL-systems) and projectile fragment separators provide a wide variety of radioactive ions with energies in the keV to the several MeV ranges. For high resolution radio frequency and optical spectroscopy the ions must be decelerated to low energies and possibly injected into an ion trap. With this goal in mind we have made simulations of ion orbits under the influence of strong focusing by inhomogeneous RF fields and decelerating DC fields. The operation of the segmented linear ion guide, the ion carpet, and the ion funnel are discussed. The optimum operating parameters of these devices are obtainedmore » using computer simulations with SIMION software.« less