Femtosecond spectroscopy of primary charge separation in modified reaction centers of <i>Rhodobacter sphaeroides</i> (R‐26)

Чекалин, С. В.; Matveetz, Ya.A.; Shkuropatov, A. Ya.; Шувалов, В.А.; Yartzev, A.P.

doi:10.1016/0014-5793(87)80698-1

Cited by 73 publications

(28 citation statements)

References 16 publications

(1 reference statement)

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“…25 Moreover, the primary electron transport is essentially unaffected in these chemically modified RCs. 16,24, 26 We also note that the shape and position of the P-absorption band at 870 nm are unchanged, which indicates that the structure of the primary donor remains intact. Thus, we conclude that the borohydride treatment induces changes in the M-subunit 17 in the immediate vicinity of the binding pocket of the chromophore, which results in the observed blue-shift of the B B absorption.…”

Section: Resultsmentioning

confidence: 87%

Subpicosecond Excited-State Relaxation of the Accessory Bacteriochlorophylls in Native and Modified Reaction Centers of Rb. sphaeroides R26

et al. 1997

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Energy transfer within native and borohydride treated (chemically modified) reaction centers (RCs) isolated from Rhodobacter sphaeroides R26 was investigated, in particular from the excited accessory bacteriochlorophylls (B*) to the primary donor (P). The decay kinetics of chemically modified and native RCs show some similarities as well as distinct differences. In reduced RCs, B* decays with a time constant of 100 fs, both in native and in modified RCs, followed by a partial recovery of the bleaching with a time constant of about 3 ps due to charge separation. In native RCs, however, an induced absorption is observed with a maximum at a delay of 500 fs, which is absent in chemically modified RCs. The initial bleaching in modified and in native RCs is characterized by an anisotropy of 0.4. After the excitation is transferred from B* to P, the anisotropy in modified RCs is decreased to a value of about 0.2. In native RCs the time-resolved anisotropy varies and depends strongly on the wavelength of detection. These observations are analyzed and discussed in terms of the individual contributions of B A and B B to the absorbance kinetics at different wavelengths. In oxidized RCs, in addition to a fast relaxation of about 100 fs in the decay of B*, we observed, a decay component with a time constant of ∼400 fs.

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Section: Resultsmentioning

confidence: 87%

Subpicosecond Excited-State Relaxation of the Accessory Bacteriochlorophylls in Native and Modified Reaction Centers of Rb. sphaeroides R26

et al. 1997

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“…sphaeroMes [24]. (3) Electron transport is unimpaired in borohydride-treated RC [35][36][37][38][39]. (4) Borohydride modification is inhibited in wild-type RC, which contain one carotenoid per RC, bound in close proximity to and apparently protecting the BChl in B M [2,4].…”

Section: Discussionmentioning

confidence: 99%

Modified bacterial reaction centers. 4. The borohydride treatment reinvestigated: comparison with selective exchange experiments at binding sites BA,B and HA,B

Struck¹,

Müller²,

Scheer³

1991

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Pigments of borohydride-treated reaction centers of Rhodobacter sphaeroides R 26 and Rhodopseudomonas viridiswere analyzed by HPLC with polychromatie detection. In both species, pigment composition and contents were unchanged. Reaction centers from Rhodobacter sphaeroides R26 were prepared in which bacteriochlorophylls (B A B) and bacteriopheophytins (HA, n) were exchanged with their potential borohydride products reduced at C-3 t.[3-Hydroxyethyl]-BChl a exchanges selectively into the BA, B pockets, and 31-OH-BPh a to the HA, B pockets. Stable reaction centers are obtained in both cases. A comparison of the absorption and circular dichroism spectra of reaction centers after exchange with 31-OH pigments, and of borohydride-modified reaction centers, reveal distinct differences. It is concluded that during borohydride reduction none of the pigments is chemically modified or extracted from the reaction centers.

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“…A key issue is whether electronic coupling among the six chromophores is sufficiently strong so as to be a principal determinant of the ground state and transient state spectra. The role of the accessory pigment BChlL in the initial photochemistry also is somewhat controversial; arguments both for [2,3] and against P+BChli being a resolved intermediate state between P* and P+BPhL have been presented from recent subpicosecond measurements.…”

Section: Introductionmentioning

confidence: 99%

Subpicosecond characterization of the optical properties of the primary electron donor and the mechanism of the initial electron transfer in Rhodobacter capsulatus reaction centers

Kirmaier

Holten

1988

FEBS Letters

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The optical difference spectrum of the excited primary electron donor, P*, in Rb. capsulatus reaction centers has been measured 600 fs after a 350‐fs flash at 870 nm. The spectrum is characterized by bleaching in the ground state absorption bands at 855 and 600 nm, and a weak featureless transient absorption in between. The lack of significant (if any) bleaching at 800 nm indicates that P does not contribute appreciable oscillator strength to the 800‐nm ground state absorption band. The conversion of P* to P+BPH− L is accompanied by isosbestic points in the transient difference spectra at 765 and 798 nm. The existence of the longer‐wavelength isosbestic point, occurring essentially at the near‐infrared absorbance maximum of the accessory BChls, provides compelling evidence that if state P*BChl− L forms, its transient concentration is exceedingly small. At certain wavelengths in the near‐infrared the absorption changes develop somewhat more slowly than the rate at which P* decays, a finding that may reflect a contribution from readjustments in the pigment‐protein complex in response to electron transfer.

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Femtosecond spectroscopy of primary charge separation in modified reaction centers of Rhodobacter sphaeroides (R‐26)

Cited by 73 publications

References 16 publications

Subpicosecond Excited-State Relaxation of the Accessory Bacteriochlorophylls in Native and Modified Reaction Centers of Rb. sphaeroides R26

Subpicosecond Excited-State Relaxation of the Accessory Bacteriochlorophylls in Native and Modified Reaction Centers of Rb. sphaeroides R26

Modified bacterial reaction centers. 4. The borohydride treatment reinvestigated: comparison with selective exchange experiments at binding sites BA,B and HA,B

Subpicosecond characterization of the optical properties of the primary electron donor and the mechanism of the initial electron transfer in Rhodobacter capsulatus reaction centers

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