Abstract
Triplet state electron paramagnetic resonance (EPR) experiments have been carried out at X-band on Rb. sphaeroides R-26 reaction centers that have been reconstituted with the carotenoid, spheroidene, and exchanged with 132-OH-Zn-bacteriochlorophyll a and [3-vinyl]-132-OH-bacteriochlorophyll a at the monomeric, lsquoaccessoryrsquo bacteriochlorophyll sites BA,B or with pheophytin a at the bacteriopheophytin sites HA,B. The primary donor and carotenoid triplet state EPR signals in the temperature range 95–150 K are compared and contrasted with those from native Rb. sphaeroides wild type and Rb. sphaeroides R-26 reaction centers reconstituted with spheroidene. The temperature dependencies of the EPR signals are strikingly different for the various samples. The data prove that triplet energy transfer from the primary donor to the carotenoid is mediated by the monomeric, BChlB molecule. Furthermore, the data show that triplet energy transfer from the primary donor to the carotenoid is an activated process, the efficiency of which correlates with the estimated triplet state energies of the modified pigments.
Item Type: | Journal article |
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Keywords: | bacteriochlorophyll - energy transfer - modified pigment - photoprotection - pigment exchange - primary donor |
Faculties: | Biology |
Subjects: | 500 Science > 570 Life sciences; biology |
URN: | urn:nbn:de:bvb:19-epub-2388-4 |
Item ID: | 2388 |
Date Deposited: | 20. Mar 2008, 14:43 |
Last Modified: | 29. Apr 2016, 08:51 |