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2011-05-07T13:52:55Z 2011-05-07T13:52:55Z Wraight, Colin A. Neshich, Goran 10000-01-01 1989 Bacterium Rhodopseudomonas viridis has four c-type cytochromes integrated to a single protein subunit of the reaction center complex. Two of them are high redox midpoint potential hemes (cyt-c559; Em = 380 mV and cyt-c556; Em = 310 mV) and other two are low midpoint potential hemes (cyt-c552; Em = 0 mV and cyt-c554; Em = $-$60 mV). The temperature dependence of the rate of oxidation of high potential cytochrome following absorption of a short pulse of light from a ruby laser has been measured spectrophotometrically. At redox potential Eh about 200 to 250 mV both high potential cytochromes are capable of donating an electron to the oxidized primary donor. Under these conditions the absorbance change observed at 554 nm is characterized by two component exponential decays due to cytochrome oxidation. The fast phase is due to electron transfer from the heme nearest to the P$\sp+$, while slow phase is explained in terms of electron sharing between the two high-potential hemes. The half times were determined to be t$\sb{1/2}$(295 K) = 1.7 $\pm$ 0.3 $\mu$s and t$\sb{1/2}$(74 K) = 10 $\pm$ 2 ms for the slow phase and t$\sb{1/2}$(295 K) = 0.18 $\pm$ 0.02 $\mu$s and t$\sb{1/2}$(74 K) = 0.41 $\pm$ 0.05 ms for the fast phase. Calculated activation energies are 8.4 Kcal/Mol for the slow phase and 10.1 Kcal/Mol for the fast phase. The effect of low potential cyt-c552 placed between two high potential hemes is on increased (about exp(22) times) probability of electron tunneling. Made available in DSpace on 2011-05-07T13:52:55Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9010969.pdf: 6969872 bytes, checksum: c9319ffe3ef5a78e7d97496e17143101 (MD5) Previous issue date: 1989 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:00:18Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:28:31-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9010969 (UMI)AAI9010969 http://hdl.handle.net/2142/22830 eng Copyright 1989 Neshich, Goran Biophysics, General Biophysical investigation of electron transfer between high-potential hemes in c subunit and special pair of reaction center protein of photosynthetic bacteria Rhodopseudomonas viridis text Biophysics and Computational Biology Biophysics and Computational Biology University of Illinois at Urbana-Champaign Dissertation Ph.D.