Reversible wavelength shifts of chlorophyll induced by a point charge

Davis, R. C.; Ditson, Susan L.; FENTIMAN, A. F.; Pearlstein, Ronald M.

doi:10.1021/ja00413a007

Cited by 48 publications

(30 citation statements)

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“…The first suggests ground-state interactions in large aggregates of Bchls in vivo accompanied by mild coupling of degenerate excited states (7)(8)(9)(10)(11)(12)(13). The second approach proposes specific interactions between the occluded Bchls and the protein side chains [e.g., interactions with charged amino residues (14) or Schiff base formation (15)] that result in modification of the chromophores (3,(16)(17)(18)(19)(20). Updated sequencing (21)(22)(23) and hydropathy plots (24) of polypeptides from several LHCs do not support this hypothesis (25).…”

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confidence: 99%

Comparative study of optical absorption and circular dichroism of bacteriochlorophyll oligomers in Triton X-100, the antenna pigment B850, and the primary donor P-860 of photosynthetic bacteria indicates that all are similar dimers of bacteriochlorophyll a

Scherz

Rosenbach-Belkin

1989

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

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Dimers of bacteriochlorophyil a (Bchla) with optical absorption maximum at 853 nm and a nonconservative circular dichroism spectrum are formed in a solution of formamide/water that contains micelles of Triton X-100. The apparent equilibrium constant and the corresponding Gibbs energy change for the Bchl self-organization are 4.9 x 10' M-l and -9.2 kcal/mol, respectively. The experimental absorption and circular dichroism spectra of the in vitro Bchl dimer (termed Bchl-853) are similar to the spectra of the bacterial light-harvesting complex B850 and the primary electron donor P-860 and probably point to a common structural motif. Indeed, simulation of the dimers' spectra (optical absorption and circular dichroism), achieved by using an extended version of the exciton theory, suggests the same geometry as recently elucidated for P-860 by x-ray diffraction crystallography. The proposed geometry is predicted to have the minimum energy in the gas phase. In conclusion, the spectral properties of the bathochromically shifted forms of Bchla are likely a result of strong dipolar interactions in self-organized structures of Bchls.Biological photosynthesis converts electromagnetic radiation into useful chemical energy by thejoint action of "antennas" and "photoreaction centers" (1). The antennas need to have a large cross section for the prevailing light absorption, stability for prolonged illumination, and the ability to transfer the collected energy with minimum dissipation and within the lifetime of the photoexcited singlet state into the site of electron allocation (1). The purple photosynthetic bacteria implement these principles by a special network of bacteriochlorophylls (Bchls), carotenoids, and polypeptide matrices termed light-harvesting complexes (LHCs) (2). Relative to their spectral properties as isolated monomers in vitro, the in vivo Bchls show a bathochromic shift of the Qy transition (2, 3) accompanied by induced optical activity (4) and increased oscillator strength (4, 5). Variations in the Qy shift of the Bchls are usually accompanied by some modifications in the polypeptide composition and characterize different LHCs (1, 6). Bacteria of the same class may share a common pool of LHCs but in different proportions. For example, the Rhodospirillaceae contain the LHCs B800-820, B800-850, B850, B870, and B890 (termed by the Qy transition of their Bchls); however, Rhodobacter sphaeroides contains mainly B800-850 and some B870, whereas Rhodospirillum rubrum contains mainly B870 (1).The various LHCs are packed around the photoreaction centers in order of descending absorption wavelength. As energy migrates from pigments absorbing at shorter wavelengths to those absorbing at longer ones a mechanism for fast energy flow is established (2). This energy is trapped by the special pair of Bchls, which functions as the primary electron donor (P). P has Qy transition at a comparable wavelength to the longest-wavelength transitions of the LHCs.Besides of a Bchla dimer has been found for which the calculated ab...

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confidence: 99%

Comparative study of optical absorption and circular dichroism of bacteriochlorophyll oligomers in Triton X-100, the antenna pigment B850, and the primary donor P-860 of photosynthetic bacteria indicates that all are similar dimers of bacteriochlorophyll a

Scherz

Rosenbach-Belkin

1989

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

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“…The aldehyde group in the position 3 can be further involved in a variety of reactions. The literature describes the chemical modification of the d-series derivatives using the reductive amination, [9,10] Wittig, [11] McMurray, [12,13] and Knoevenagel [11] reactions. Reactions of the aldehyde group of d-chlorins were used to form fluoroacyl [14] and ethenyl [15] substituents.…”

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confidence: 99%

“…It was found that thiols can catalyze the oxidation of the vinyl group to the aldehyde by air oxygen. To receive the target aldehydes (6)(7)(8)(9)(10) ¶ it is enough to use catalytic amounts of thiol (only 5-7 molar % respectively the amount of oxidized vinylchlorin). Oxidation was carried out by bubbling of air through a solution of vinylchlorin at room temperature for 1 h. The optimal oxidation conditions were worked out using methylpheophorbide a (1) as an oxidation substrate, different thiols (see Scheme 1) and various solvents (benzene, CHCl 3 , CH 2 Cl 2 and THF).…”

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confidence: 99%

Catalytic Effect of Thioles in Oxidation of the Vinyl Group to Aldehyde in Chlorophyll a Derivatives

Белых¹,

Ashikhmina²

2012

MHC

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“…Since the redox potential of a Chl dimer in solution is not sufficiently positive to drive the oxidation of water, it has been generally assumed that the redox potential of the PSII trap is determined by interactions between the chromophores and proteins. Modified Chl molecules containing point charges or the presence of charged residues near Chl may alter spectral properties or the redox potential of Chl (7)(8)(9). A survey of the amino acid sequences of the PSII core polypeptides D1 and D2 was conducted to identify conserved and potentially charged residues that could influence the electronic properties of the PSII trap.…”

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confidence: 99%

Photosynthetic electron transport in genetically altered photosystem II reaction centers of chloroplasts.

Roffey¹,

Golbeck²,

Hille³

et al. 1991

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

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Using a cotransformation system to identify chloroplast transformants in Chlamydomonas reinhardt&, we converted histidine-195 of the photosystem H reaction center D1 protein to a tyrosine residue. The mutants were characterized by a reduced quantum efficiency for photosynthetic oxygen evolution, which varied in a pH-dependent manner, a reduced capacity to oxidize artificial donors to photosystem H, and P680) reduction kinetics (microsecond) that were essentially similar to wild type. In addition, a dark-stable radical was detected by ESR in mutant photosystem II particles but not in wild-type particles. This radical was similar in g value and lineshape to chlorophyll or carotenoid cations but could have arisen from a tyrosine-195 cation. The ability of the photosystem II trap (P680) to oxidize tyrosine residues suggests that the mutant tyrosine residue could be used as a redox-sensitive probe to investigate the environment around the photosystem H trap.It is generally accepted that the photosystem II (PSII) reaction center of chloroplasts is structurally and functionally similar to the bacterial photosynthetic reaction center (1-5). Both reaction center types have two core polypeptides that coordinate the primary electron donor, presumably a chlorophyll (Chl) special pair, and the primary electron acceptors, pheophytin and the plastoquinone Qa. These polypeptides, the L and M subunit of the bacterial reaction center and the D1 and D2 subunits of PSII, have significant levels of sequence identity (25%) (6). In addition, the D1 and D2 polypeptides have the same number and orientations of transmembrane domains as the L and M subunits (3). These and other similarities suggest that the protein domains involved in the coordination of the PSII trap and binding of electron acceptors are structurally similar to those of the L and M polypeptides of the bacterial reaction center (1-3). The bacterial and PSII reaction centers, however, differ with respect to the organization of secondary electron donors and the redox potential of the reaction center traps. The Chl special pair of the bacterial reaction center is reduced by a cytochrome, whereas the PSII trap, P680', is reduced by a peptidyl tyrosine residue that in turn is reduced by electrons derived from the oxidation ofwater. Since the redox potential of a Chl dimer in solution is not sufficiently positive to drive the oxidation of water, it has been generally assumed that the redox potential of the PSII trap is determined by interactions between the chromophores and proteins. Modified Chl molecules containing point charges or the presence of charged residues near Chl may alter spectral properties or the redox potential of Chl (7-9). A survey of the amino acid sequences of the PSII core polypeptides D1 and D2 was conducted to identify conserved and potentially charged residues that could influence the electronic properties of the PSII trap. We identified a potentially ionizable residue, histidine-195 (H195) of the D1 protein, which is projected to be adjacent to ...

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Reversible wavelength shifts of chlorophyll induced by a point charge

Cited by 48 publications

References 0 publications

Comparative study of optical absorption and circular dichroism of bacteriochlorophyll oligomers in Triton X-100, the antenna pigment B850, and the primary donor P-860 of photosynthetic bacteria indicates that all are similar dimers of bacteriochlorophyll a

Comparative study of optical absorption and circular dichroism of bacteriochlorophyll oligomers in Triton X-100, the antenna pigment B850, and the primary donor P-860 of photosynthetic bacteria indicates that all are similar dimers of bacteriochlorophyll a

Catalytic Effect of Thioles in Oxidation of the Vinyl Group to Aldehyde in Chlorophyll a Derivatives

Photosynthetic electron transport in genetically altered photosystem II reaction centers of chloroplasts.

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