title: Cryogenic Charge Transport in Oxidized Purple Bacterial Light-Harvesting 1 Complexes.
abstract: We report on the analysis of the inter-bacteriochlorophyll a (BChla) charge-transport process that occurs in oxidized purple bacterial light-harvesting 1 (LH1) complexes. Experimentally, charge migration within oxidized LH1 is monitored by following the temperature-dependent changes of the BChla(•)(+) electron paramagnetic resonance (EPR) line-shape characteristics. At 6 K, a Gaussian-shaped spectrum with a 1.3-mT width is detected. These characteristics indicate that at extremely low temperatures charge transport is substantially slowed so that the unpaired electron is localized on one or two BChlas. At higher temperatures, the spectra exhibit non-Gaussian line shapes and decreased line widths. These characteristics are engendered by charge migration. We have analyzed the temperature dependence of the transport process through EPR spectral simulations. The simulations incorporated a nonadiabatic model for electron transfer. The temperature dependence could be adequately described on the basis of an electron-transfer model that accounts for the effects of slow medium relaxation, whereas a satisfactory description could not be obtained on the basis of conventional multimode models for transport. The results of our analysis are consistent with the notion that the protein functions as the primary solvent for the redox centers and are in accord with the view that the protein behaves as a frozen glass, even at room temperature, with respect to the low-frequency vibrational motions coupled to electron transfer.
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: Nagarajan
authors: N
authors: Srivatsan
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: Dmitri
authors: D
authors: Kolbasov
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: Nina
authors: N
authors: Ponomarenko
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: Stefan
authors: S
authors: Weber
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: Agnes E
authors: AE
authors: Ostafin
authors: Avery Research Center, 2900 Bradley Street, Pasadena, California 91107.|Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.|Institute of Experimental Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany.|Department of Chemical Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, Indiana 46556.|Department of Chemistry and Institute of Biodynamics, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637.
authors: James R
authors: JR
authors: Norris