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Identification of the upper exciton component of the B850 bacteriochlorophylls of the LH2 antenna complex, using a B800-free mutant of Rhodobacter sphaeroides

Identification of the upper exciton component of the B850 bacteriochlorophylls of the LH2 antenna complex, using a B800-free mutant of Rhodobacter sphaeroides
Identification of the upper exciton component of the B850 bacteriochlorophylls of the LH2 antenna complex, using a B800-free mutant of Rhodobacter sphaeroides
In this paper, we report the circular dichroism (CD) spectra of two types of LH2-only mutants of Rhodobacter sphaeroides. In the first, only the wild type LH2 is present, while i the second, the B800 binding site of LH2 has been either destabilized or removed. For the first time, we have identified a band in the CD spectrum of LH2, located at approximately 780 nm, that can be ascribed to the high exciton component of the B850 band. The experimental spectra have been modeled by theoretical calculations. On this basis, the average interaction strength between the monomers in the B850 ring can be estimated to be approximately 300 cm-1. In addition, we suggest that in LH2 of Rb. sphaeroides the angles made by the Qy transitions of the B850 BChls with respect to the plane of the ring are slightly different from those calculated from the crystal structure of the Rhodopseudomonas acidophila LH2 complex.
0006-2960
4693-4698
Koolhaus, M.H.
48e368b2-d4be-4db4-9b32-cf204f7a5676
Frese, R.N.
9dafc91e-948c-4442-b88b-4dd361989502
Fowler, G.J.
f3c1bbd2-db93-4b8e-b9d7-367e3039340c
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd
Georgakopoulou, S.
13e50170-4b25-4116-8051-5930f4ba0096
van der Zwan, G.
188ee0c8-3b3a-45f1-b4c2-95b03f01f092
Hunter, C.N.
f86f3aa5-f60c-4f35-8446-afb3f0db2d43
van Grondelle, R.
1beb026c-7001-400b-8697-d0e34babf036
Koolhaus, M.H.
48e368b2-d4be-4db4-9b32-cf204f7a5676
Frese, R.N.
9dafc91e-948c-4442-b88b-4dd361989502
Fowler, G.J.
f3c1bbd2-db93-4b8e-b9d7-367e3039340c
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd
Georgakopoulou, S.
13e50170-4b25-4116-8051-5930f4ba0096
van der Zwan, G.
188ee0c8-3b3a-45f1-b4c2-95b03f01f092
Hunter, C.N.
f86f3aa5-f60c-4f35-8446-afb3f0db2d43
van Grondelle, R.
1beb026c-7001-400b-8697-d0e34babf036

Koolhaus, M.H., Frese, R.N., Fowler, G.J., Bibby, T.S., Georgakopoulou, S., van der Zwan, G., Hunter, C.N. and van Grondelle, R. (1998) Identification of the upper exciton component of the B850 bacteriochlorophylls of the LH2 antenna complex, using a B800-free mutant of Rhodobacter sphaeroides. Biochemistry, 37 (14), 4693-4698. (doi:10.1021/bi973036l).

Record type: Article

Abstract

In this paper, we report the circular dichroism (CD) spectra of two types of LH2-only mutants of Rhodobacter sphaeroides. In the first, only the wild type LH2 is present, while i the second, the B800 binding site of LH2 has been either destabilized or removed. For the first time, we have identified a band in the CD spectrum of LH2, located at approximately 780 nm, that can be ascribed to the high exciton component of the B850 band. The experimental spectra have been modeled by theoretical calculations. On this basis, the average interaction strength between the monomers in the B850 ring can be estimated to be approximately 300 cm-1. In addition, we suggest that in LH2 of Rb. sphaeroides the angles made by the Qy transitions of the B850 BChls with respect to the plane of the ring are slightly different from those calculated from the crystal structure of the Rhodopseudomonas acidophila LH2 complex.

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Published date: 7 April 1998

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Local EPrints ID: 37566
URI: https://eprints.soton.ac.uk/id/eprint/37566
ISSN: 0006-2960
PURE UUID: 4c673626-cae3-4c11-98e4-f115db085d18

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Date deposited: 23 May 2006
Last modified: 11 Jul 2017 09:46

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