The preparation and characterization of chloroplast fragments having an absorbancy maximum at 7400 A

Lippincott, James A.; Aghion, Jacques; Porcile, Evelyne; Bertsch, Walter F.

doi:10.1016/0003-9861(62)90140-6

Cited by 19 publications

(6 citation statements)

References 15 publications

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“…It must be noted that the C750 aggregates and C670 in PYR and THF-water mixtures are not physiologically important species. They are only observed during the treatment of chloroplast fragments (5) or chlorosomes (3). As is evident from the comparison of absorption characteristics of Chl a-enriched preparations and Chl b-less mutants with those of the C670 aggregates studied here (Table 6), only the precursor of the C750 aggregates, i.e.…”

supporting

confidence: 51%

“…In addition to his hypothesis, we point out that only a metastable Chl organization, i.e. Chl aggregate organization at the boundary of its stability, could explain the finding that antenna Chl a has a structural role in stabilizing the functional conformation of P700-chlorophyll-protein complexes (57), as well as the appearance of 740 nm Chl forms during the treatment of chloroplast fragments with kosmotropic solvents (5).…”

mentioning

confidence: 70%

“…One of the reasons is that the mechanism for Chl selfassembly in aqueous media is also unclear. That such knowledge is of importance is evident by the same effects that medium composition has on both the chlorosomes (3) and Bchl c and d aggregates in aqueous media (4) or on chloroplast fragments (5) and Chl a aggregates in aqueous solvents (6). While the formation of Chl aggregates in various organic solvent-water mixtures is well documented (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), little is known about the contribution of the structure and properties of the medium for the assembly and stabilization of different Chl aggregate organizations in aqueous media.…”

Section: Introductionmentioning

confidence: 99%

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Chlorophyll a Self-assembly in Polar Solvent–Water Mixtures†

Vladkova

2000

Photochem Photobiol

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confidence: 51%

mentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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Chlorophyll a Self-assembly in Polar Solvent–Water Mixtures†

Vladkova

2000

Photochem Photobiol

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“…Treatment of green plant chloroplasts with 65% aqueous methanol converts the natural 680 nm absorption peak to 740 nm (28), which exactly parallels the optical changes when Chla oligomers in octane solution are converted by addition of water to P740 micelles. It is possible, therefore, that in organisms containing Chla as their sole chlorophyll, most of the Chla occurs as water-free oligomers, (Chla), (6), that are the precursors of the P740 species formed by hydration.…”

Section: Resultsmentioning

confidence: 74%

Small-angle neutron scattering studies of chlorophyll micelles: Models for bacterial antenna chlorophyll

Worcester

Michalski

Katz

1986

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

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Micelles of hydrated chlorophyll a (P740), bacteriochlorophyll a (P865), bacteriochlorophyll c (P750), and pheophytin a prepared in organic media have been studied by small-angle neutron scattering to determine their shape, size, and mass per unit length. All of the micelles are hollow cylinders of well-defined size. The P740 and P750 cylinders are essentially monolayers of macrocycles crosslinked by water, probably in an arrangement similar to that of crystals of chlorophyll derivatives. The P865 micelle is more nearly a bilayer of macrocycles. We show that the curvature necessary to form cylinders probably results from intrinsic curvature of the five-coordinated chlorophyll macrocycle. Studies of P740 micelle formation and the disaggregating effects of another nucleophile (pyridine) are described. As the P750 micelles are nearly identical in size and optical spectra to the rod-shaped structures observed in chlorosomes, and the P865 micelles have optical properties very similar to the in vivo properties of the long-wavelength antenna of purple photosynthetic bacteria, we propose that features of the hydrated cylindrical micelles of these chlorophylls provide good models for antenna chlorophyll in photosynthetic bacteria.Many artificial chlorophyll systems (colloidal dispersions, films, monolayers, adsorbates) are of interest because their visible absorption maxima are red-shifted relative to the corresponding monomeric chlorophyll, a feature that is also characteristic of chlorophylls in vivo (1). Of particular importance are the chlorophyll/water micelles formed in nonpolar organic solvents. Chlorophyll a/water micelles so formed are red-shifted from 660 nm (monomer) to 740 nm and are photoactive in red light (2). Bacteriochlorophyll a/water micelles (P865) have red-shifted optical spectra that strongly resemble those of intact purple photosynthetic bacteria (3). As no direct structural information on these systems exists, we have undertaken a small-angle neutron-scattering study of chlorophyll/water micelles in organic media, using the In- MATERIALS AND METHODS Materials. Chlorophyll a (Chla), bacteriochlorophyll a (Bchla), Chlorobium chlorophyll (Bchlc), and pheophytin a (Pheoa) were prepared by literature methods (4). Purity was established by HPLC and by californium-252 plasma desorption mass spectroscopy (5). Deuterated solvents (Aldrich) contained <1% 1H.Chlorophyll/water micelles were prepared by addition of microliter amounts of 'H20 or 2H20 to previously dried chlorophyll dissolved (=10 mg/ml) in a nonpolar solvent.Mild sonication (30 sec) was used to disperse the water. Rigorous drying of the chlorophylls and the solvents (6) before hydration was necessary as the structures formed from undried or partially dried starting materials can vary. Samples for small-angle neutron scattering were sealed in 2-to 5-mm-thick quartz cells. Neutron Scattering. Chlorophylls of natural isotopic composition were studied in deuterated solvents to enhance the scattering intensity in much the same way neutrons h...

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“…band of crystalline chlorophyll-a discovered by Jacob, Vatter & Holt (14). This crystalline chlorophyll does, however, ap pear to be the "740 mIL pigment" produced in leaf extracts by Lippincott et al (248). In summary, it is evident that, except for the absorption at 700 to 70S, the detectable absorption bands beyond the chlorophyll-a maxi mum are special cases found in certain algae and generally at low concen tration.…”

Section: Far-red Effects Related To Photosynthesismentioning

confidence: 89%