Homogeneous linewidth and optical dephasing of the S1 ← So transition of magnesium porphin in an n-octane crystal: A study by transient and photochemical hole-burning

Dicker, A.I.M.; Johnson, Lawrence W.; Völker, S.; Waals, J.H. van der

doi:10.1016/0009-2614(83)87252-2

Cited by 29 publications

(19 citation statements)

References 28 publications

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“…We note that the energy differences between the spectral positions of the holes burned in B820 and B777 and their respective "photoproducts" are very similar to the ∼100 cm -1 previously obtained by hole burning for magnesium porphin in an n-octane crystal 30 and for BChl-a in glasses. 20 We believe that not only in Mg-porphin and BChl-a in glasses, but also in the B820 and B777 subunits, it is the external ligation of the Mg atom which, after hole burning, has changed.…”

Section: Hole Burning: Determination Of Phonon Sidebands and Photoprosupporting

confidence: 83%

“…30 We conclude that in both subunits a change in the external ligation of the central Mg atom in the BChl-a molecule occurs with respect to the surrounding protein. Since the quantum yield for this process appears to be an order of magnitude larger for B777 than for B820, we believe that the B777 monomer has a weaker coupling to the protein than the B820 dimer.…”

Section: Discussionmentioning

confidence: 73%

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Spectral Hole Burning and Fluorescence Line Narrowing in Subunits of the Light-Harvesting Complex LH1 of Purple Bacteria

Creemers¹,

De²,

Visschers³

et al. 1999

J. Phys. Chem. B

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Spectroscopic properties of the B820 and B777 subunits of the core light-harvesting complex LH1 of purple bacteria Rhodospirillum rubrum G9 were studied by hole burning (HB) and fluorescence line narrowing (FLN) between 1.2 and 4.2 K. We have found that an equilibrium exists between the three forms B820, B777, and the native LH1-complex in the presence of the detergent n-octyl--D-glucopiranoside (OG). The shift of this equilibrium was followed as a function of OG concentration by means of absorption and fluorescence spectra. Low-frequency modes at 19 cm -1 for B820 and at 25 cm -1 for B777 were identified by FLN. From the spectral position of these modes as a function of excitation wavelength λ exc and from the homogeneous line width Γ′ hom as a function of λ exc , we conclude that "downhill" energy transfer does not take place either among B820 or among B777 subunits. The temperature dependence of Γ′ hom , however, indicates that optical dephasing and/or spectral diffusion does occur in these subunits. The positions of side holes and antiholes, furthermore, suggest that the hole-burning mechanisms in B820 and B777 are similar, although their HB efficiencies differ by a factor of 10. IntroductionLight-harvesting (LH) complexes in purple bacteria are responsible for the efficient collection of sun light and the transfer of excitation energy to the reaction center (RC) in photosynthesis. The primary charge separation occurs in the RC and leads to the subsequent conversion of excitation energy into a chemically useful form. Most purple bacteria contain two types of LH complexes: the LH1 core complex surrounding each RC and peripheral LH2 complexes which absorb slightly further to the blue and transfer the excitation energy to LH1. 1 Both the LH1 and LH2 complexes have ringlike structures 2,3 containing a basic repeating subunit. This subunit consists of a dimer of bacteriochlorophyll-a (BChl-a) molecules bound to two helical polypeptides (R and ), each comprising ∼50 amino acids 4 with a protein mass of approximately 6 kDa. The circular arrangement of the reconstituted LH1 in Rhodospirillum rubrum G9 is built up from 16 subunits. It has an outer diameter of 116 Å and an inner diameter of 68 Å, probably enclosing the RC. 2 The LH1 complex (B873) can be reversibly dissociated into its constituent subunits by detergent titration. 5,6 The detergent, n-octyl--D-glucopyranoside (OG), forms micelles which enclose either the dimeric subunit, called B820 (if ∼1.2% OG is used) or the B777 monomer subunit (when ∼5% OG is used). Reassociation of the subunits yields an aggregate with a spectrum nearly identical to that of LH1. 5,7 Although the absorption spectrum and the fluorescence lifetime of B777 are similar to those of BChl-a in solution, 8,9

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Section: Hole Burning: Determination Of Phonon Sidebands and Photoprosupporting

confidence: 83%

Section: Discussionmentioning

confidence: 73%

Spectral Hole Burning and Fluorescence Line Narrowing in Subunits of the Light-Harvesting Complex LH1 of Purple Bacteria

Creemers¹,

De²,

Visschers³

et al. 1999

J. Phys. Chem. B

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“…Thus, rhom = (2nT,) -1 when T -+ 0 (15,53). The same result was found by HB for other porphin molecules in n-alkane hosts: ZnP in n-Cg (33), chlorin in n-C6, n-Cg, and n-CIO (37), H2P in n-C IO (55), and MgP in n-Cs (34). By contrast, photon echo decay times, 1T 2 , obtained for the S I <-So 0-0 transitions of tetracene and pentacene in p-terphenyl (82), naphthalene in durene and perdeutero-naphthalene (83), and pentacene in naphthalene (84) at l.4K were claimed not to be determined by T 1 • It was suggested that not all relaxation processes in these organic crystals were frozen out at the lowest temperature (82).…”

Section: Crystalline Hostssupporting

confidence: 83%

“…TRANSIENT HOLE·BURNING (THB) (12,33,34,52) In this process, population is transferred from the ground state through the excited state of interest to a metastable state. The latter may either be the same excited state, a long living triplet state, or a hyperfine level of the ground state.…”

Section: Mechanismsmentioning

confidence: 99%

“…Transient hole-burning may either be performed with one or two single frequency cw dye lasers, depending on the lifetime of the metastable level (12,33,34,52). If two lasers are used, the first one burns the hole at a fixed frequency, whereas the second, at lower intensity, scans the excitation spectrum of the hole either during burning or after a delay time.…”

Section: Techniquesmentioning

confidence: 99%

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