Structure of Rhodopseudomonas viridis reaction centers. Absorption and photoselection at low temperature

Vermeglio, A.; Paillotin, Guy

doi:10.1016/0005-2728(82)90275-4

Cited by 98 publications

(31 citation statements)

References 17 publications

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“…In fact, the difference absorbance spectrum of wavelength. This observation agrees with the interpretation that the absorption at 850 nm represents the second dlmer band of the special parr [1,9,10]. CD investigations [11], studies of oriented cells [12], and our measurements on crystals with polarized light (see below) lead to the same conclusions The small absorption band at 680 nm is an oxidation product of BChl b [2].…”

supporting

confidence: 91%

“…They have their major Qv absorption perpendicular to the z-axJs. The Qx transntlon of the same molecules give rise to the enhanced absorption m the Eli spectrum at 600 nm (in) The two BPh b molecules absorb at 790 and 810 nm, according to the literature [9] Our absorpuon data of the Ell spectrum show a maximum at 805 nm and a shoulder around 780 nm. Furthermore, m the E± spectrum a shoulder appears around 800 nm These data suggest that the BPh b molecules have an orientation substantially different from that of the BChl b molecules.…”

supporting

confidence: 54%

“…The optical absorption spectrum of reaction center crystals from Rps vmdls is presented in Fig la (broken line) Quahtatlvely, the difference spectrum is smular to that in pubhshed data on reaction centers in solution, but the dlchrolsm of the crystals (see below) gives rise to quantitative changes (e.g., at 960 and around 830 nm) [3,9,13].…”

mentioning

confidence: 73%

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Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Zinth¹,

Kaiser²,

Michel

1983

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Crystallized reaction centers from Rhodopseudomonas viridis (i) are photochemicaily active with electron transfer from the special pair to the quinones, (ii) show dichroism giving valuable.information on the orientation of the different chromophores and (iii) allow chemical treatment in the crystalline phase.In the past, reaction centers from photosynthetic bacterm have been investigated m intact cells, in photosynthetic membranes or isolated m detergent solutions. Comparison of the optical spectra of intact cells with those of isolated reaction centers suggested that careful ~solatlon does not seriously affect the properties of the reaction centers [1][2][3][4][5][6]. The spectral properues and the pigment composmon of isolated reaction centers from Rhodopseudomonas vtrtdts have been studied extenswely [1-6] Recently, the photosynthetic reaction centers from thas photosynthetic bacterium were crystallized [7]. In this paper we report on the properties of these crystals Reaction centers isolated w~th the detergent N,N-dlmethyldodecylarmne N-oxide contain four BChl b and two BPh b molecules [1] The primary electron donor, called P-960 due to its maxamum of absorbance, is made up of two of the four BChl b molecules, whale the 'primary' electron acceptor is a qulnone-lron complex [1]. There are one menaqumone and one to two ub~qumones per P-960 [8]. Isolated reacUon centers from Rps vtrt-A bbrevlatlons BChl, bactenochlorophyll, BPh, bactenopheophytm dts also contain four heme groups (two 'cytochrome c-558' and two 'cytochrome c-553'), wluch are probably bound to the same protein subumt [6], They feed electrons to P-960 +.The reaction centers were ~solated as described recently with the following modification [7]. For the molecular sieve chromatography step we used as column material Fractogel TSK HW 55 S (Merck, Darmstadt), thus step was repeated. In contrast to earher preparations [7] using different column material, we now observe bleaching of P-960 upon lllumanatlon Thus finding indicates that the qumones are still present in the new preparations. The crystals were grown as described previously [7]. The space group of these crystals IS P4~(3)2~2 with a tetragonal unit cell dlmens~on of 223 × 223 x 114 ,~ containing eight asymmetric umts per crystallographac umt cell. The volume of the asymmetric umt and the molecular wetght of the reactton centers make it more hkely that each asymmetric umt ~s occupied by two reaction center molecules than by one or three With these figures were calculate 2.8-l0 )8 reaction center molecules per cm 3, corresponding to 4.7-l0 -3 mol/1. In space group P41(3)212, a 4-fold screw axas is parallel to the z-direction whereas nomntersectlng 2-fold screw axes (perpen&cular to the 4-fold axis) are 0005-2728/83/0000-0000/$03 00

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supporting

confidence: 91%

supporting

confidence: 54%

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Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Zinth¹,

Kaiser²,

Michel

1983

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…Because the absorption bands for the monomeric chromophores overlap substantially and one expects vibronic bands from the special pair in this region, it is difficult to quantitate IAL (19,20), and this shoulder has been ascribed by some to the Pt Be chargetransfer state (20). Measurements of delayed fluorescence (21) and the temperature dependence of the 3P decay rate (22) for Rb. (Fig.…”

Section: Resultsmentioning

confidence: 99%

Stark effect spectroscopy of Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centers

Lockhart

Boxer

1988

Proc. Natl. Acad. Sci. U.S.A.

134

129

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The nature of the initially excited state of the primary electron donor or special pair has been investigated by Stark effect spectroscopy for reaction centers from the photosynthetic bacteria Rhodopseudomonas viiis and Rhodobacter sphaeroides at 77 K. The data provide values for the magnitude of the difference in permanent dipole moment between the ground and excited state, IAuI and the angle C between ApL and the transition dipole moment for the electronic transition.IAdA and C for the lowest-energy singlet electronic transition associated with the special pair primary electron donor were found to be very similar for the two species. IA|I for this transition is substantially larger than for the Qy transitions of the monomeric pigments in the reaction center or for pure monomeric bacteriochlorophylls, for which Stark data are also reported. We conclude that the excited state of the special pair has substantial charge-transfer character, and we suggest that charge separation in bacterial photosynthesis is initiated immediately upon photoexcitation of the special pair. Data for Rhodobacter sphaeroides between 340 and 1340 nm are presented and discussed in the context of the detection of chargetransfer states by Stark effect spectroscopy.The recent elucidation of the organization of the reactive components in reaction centers (RCs) from photosynthetic bacteria by x-ray diffraction (1)(2)(3)(4) makes possible an analysis of the initial charge-separation mechanism from first principles. The first step in such an analysis is the calculation of the spectroscopic properties of the RC from several species, including the absorption, circular dichroism, and linear dichroism spectra (5-9). In a recent report we demonstrated that a quantitative analysis of the effect of an electric field on the absorption spectrum (the Stark effect spectrum) in Rhodobacter sphaeroides RCs at room temperature provides additional observables for comparison with theory (10). This work followed up on an earlier preliminary report by deLeeuv et al. (11). In the present communication we extend these measurements to a different species, Rhodopseudomonas viridis, and to low temperatures (12).Quantitative analysis of the Stark effect spectrum provides information on the magnitude of the difference in permanent dipole moment between the ground and excited state, JAput, and on the angle, (, between Ap and the transition dipole moment.Since the orientation of the transition dipole moment can be determined relative to the molecular axes from single-crystal polarized absorption measurements, the angle (can be related to the movement of charge associated with excitation of the chromophores in the RC. Stark effect data have also been obtained for monomeric photosynthetic chromophores, and this information should be useful for testing the reliability ofthe wave functions that are used for the calculation of RC spectral properties and electron transfer pathways. EXPERIMENTAL Rps. viridis RCs were prepared as previously described for Rb. sphaeroides (...

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“…sphaeroides (13) and Rps. viridis (17,19) RCs is split into two electronic transitions separated by -0.02 eV (17). Since the long-wavelength transition is very sensitive to the charge on the H1 molecule (17,19), it was suggested (17) that this transition is pE(qA) +-PB.…”

Section: Discussionmentioning

confidence: 99%

Primary electron transfer reactions in modified reaction centers from Rhodopseudomonas sphaeroides

Шувалов

Duysens

1986

Proc. Natl. Acad. Sci. U.S.A.

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Absorption spectra were measured by means of an optical multichannel analyzer in Rhodopseudomonas sphaeroides R-26 reaction centers (RCs) modified by treatment with NaBH4 at various times (21 pS) after the onset of a short excitation flash at 880 nm. Most of these RCs (75-95%) have only one "monomeric" bacteriochlorophyll-800 (B1) molecule and are as active as the original RCs. The duration of the excitation and measuring pulses was "33 ps. Ifthe center ofthe excitation pulse preceded the center of the measuring pulse by 3640 ps, the formation of a state pE (early state), which is converted to the state PF (PI bacteriopheophytin) in 4 ± 1 ps (l/e time), was observed. Also the kinetics and the spectrum of the stimulated emission (reflecting the kinetics and the emission spectrum of the excited state P*) were determined. The difference spectrum of the state pE approximately equals the sum of the spectra of the states P* (m65%) and l[P+B-] (m35%). This indicates that B-is an intermediate in the electron transfer from P* to bacteriopheophytin, H1, transferring this electron with a rate constant of (4 x 0.35 ps)-' = 7 X loll s-.Reaction centers (RCs) of purple bacteria contain one bacteriochlorophyll (BChl) dimer (P), two BChl monomers absorbing at about 800 nm (B1 and B2), two bacteriopheophytins (Bph) (H1 and H2), two quinones (QA and QB), and one atom of Fe (1-3). P, the primary electron donor with an absorption band at 860 nm, one of both monomers, B, absorbing at 802 nm, H1, the component absorbing at 545 and 760 nm, and QA participate in the primary electron transfer reactions, which occur in =1-200 ps in a wide range of temperatures (1-300 K).Recently, evidence was obtained from which it was concluded that the B molecule is the primary acceptor in electron transfer (4). This BChl transfers an electron to H1 in a few picoseconds, with the formation ofP+Hj (5). This conclusion was (see ref. 6), as will be discussed, erroneously criticized by other laboratories.Optical measurements and x-ray analysis of Rhodopseudomonas viridis and Rhodopseudomonas sphaeroides R-26 RCs (7-9) have shown that only one BChl monomer (B1) is present between P and H1. Whether B2 participates in the electron transfer reactions was not clear. This paper presents results that show that, at an early delay (-36 to -40 ps), the 33-ps excitation at 880 nm of R-26 RCs from which B2 has been extracted (9) induces the formation of a state pE with a relative bleaching of 50% of the 803-nm band with respect to that of the 870-nm band (the "molecular" ratio is 0.35). In this state the bleaching of the H1 bands is not observed. We have concluded that B1, and not B2, participates in the primary electron transfer; the earliest observable state pE is a quantum mechanical mixture of the states P B-for 35% and P* for 65%, which is important for the mechanism of electron transfer. The rate of electron transfer between Bj and H1 was calculated, and further details of the electron transfer mechanism were elucidated. MATERIALS AND METHODSRCs from Rps...

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Structure of Rhodopseudomonas viridis reaction centers. Absorption and photoselection at low temperature

Cited by 98 publications

References 17 publications

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Efficient photochemical activity and strong dichroism of single crystals of reaction centers from Rhodopseudomonas viridis

Stark effect spectroscopy of Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centers

Primary electron transfer reactions in modified reaction centers from Rhodopseudomonas sphaeroides

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