Chlorophyll-chlorophyll and chlorophyll-water interactions in the solid state.
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Bacteria↗
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[Electrochemical study of chlorophyll. III. Effect of the medium on redox potential of the system chlorophyll-chlorophyll anion-radical].
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Alcohols↗
[Aggregated forms of chlorophyll a, chlorophyll b and beta-carotene in monolayers and membranes; the migration of energy between them and within the complex (chlorophyll a + beta-carotene)].
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Carotenoids↗
Organization of chlorophyll a in bilayer membranes. The chlorophyll a/dimyristoylphosphatidylcholine system.
In order to investigate the relative importance of the hydrophobic and headgroup interactions of chlorophyll a in phospholipid bilayers, we have carried out differential scanning calorimetry (DSC) and deuterium (2H) and phosphorus (31P) nuclear magnetic resonance (NMR) experiments on the multilamellar system of chlorophyll a in dimyristoylphosphatidylcholine (DMPC). Compared to the phytol chain of chlorophyll and the previously reported distearoylphosphatidylcholine (DSPC), the acyl chains of DMPC are shorter in length by three and four carbons, respectively. A lowering in the phase-transition temperature was observed for the DMPC multilayers in the presence of chlorophyll a in the DSC thermograms and in the 31P chemical shift anisotropy measurements. These results, together with data on hydrophobic interactions as measured by 2H-NMR and on headgroup interactions as evidenced from 31P-NMR, suggest a phase diagram for the chlorophyll a/DMPC system in which phase separation readily occurs between a chlorophyll-rich compound phase and a chlorophyll-poor phospholipid phase. Compound formation appears to be important in the stabilization of chlorophyll a in bilayers with shorter chains.
Calorimetry, Differential Scanning↗
Are bryophytes shade plants? Photosynthetic light responses and proportions of chlorophyll a, chlorophyll b and total carotenoids.
BACKGROUND AND AIMS: Data are presented from 39 species of mosses and 16 liverworts for ratios of chlorophylls and total carotenoids, and light saturation of photosynthetic electron flow or photosynthetic CO2 uptake, in relation to the postulate that bryophyte cells in general show shade-plant characteristics. METHODS: Pigment concentrations were measured by spectrophotometer in 80 % acetone extracts. Light-saturation curves were constructed by (modulated) chlorophyll florescence and for some species by infra-red gas analysis. KEY RESULTS: The pigment measurements were widely variable but broadly in line with the findings of previous authors. Median values (mosses/liverworts) were: total chlorophyll, 1.64/3.76 mg g(-1); chlorophyll a : b, 2.29/1.99; chlorophylls : carotenoids, 4.74/6.75). The PPFD values at 95 % saturation (estimated from fitted curves) also ranged widely, but were almost all <1000 micromol m(-2) s(-1); the median for mosses was 583 and for liverworts 214 micromol m(-2) s(-1). The two highest PPFD95% values were from Polytrichum species with lamella systems forming a ventilated photosynthetic tissue. Total chlorophyll, chlorophyll a : b and chlorophylls : carotenoids all correlated significantly with PPFD95%. CONCLUSIONS: Bryophytes include but are not inherently shade plants. Light-saturation levels for species of open sun-exposed habitats are lower than for vascular sun plants and are probably limited by CO2 diffusion into unistratose leaves; this limit can only be exceeded by bryophytes with ventilated photosynthetic tissues which provide increased area for CO2 uptake.
Bryophyta↗
Increase of the chlorophyll fluorescence ratio F690/F735 during the autumnal chlorophyll breakdown.
The chlorophyll content and the fluorescence induction kinetics at two wavelengths (690 nm and 735 nm) have been measured in leaves of nine common broadleaf tree species during the autumnal chlorophyll breakdown. The ratio of the chlorophyll fluorescence maxima F690/F735 was determined at fluorescence maximum (fm) and at steady-state conditions (fs) by the laser-induced fluorescence emission using the two-wavelength fluorometer. The ratio F690/F735 increases with the leaf discolouring during the autumnal chlorophyll breakdown. The relationship between the chlorophyll content and the ratio F690/F735 can be expressed by a power function (curvilinear relationship) which is valid for all the species examined. In most cases the ratio F690/F735 measured in the upper leaf side is lower than that in the lower leaf side, but the trend is the same along the decreasing chlorophyll content. The ratio F690/F735 is always higher at maximum fluorescence than at steady-state fluorescence in the upper as well as lower leaf side and these values are well fitted in a linear correlation. This study confirms the usefulness of the ratio F690/F735 as a suitable non-destructive indicator of the in-vivo chlorophyll content, especially at medium and low chlorophyll content.
Chlorophyll↗
Chlorophyll in a Synechocystis sp. PCC 6803 mutant without photosystem I and photosystem II core complexes. Evidence for peripheral antenna chlorophylls in cyanobacteria.
The chlorophyll protein organization has been investigated in thylakoid membranes from mutants of the cyanobacterium Synechocystis sp. PCC 6803, in which the photosystem II (PS II) genes psbB and/or psbC (coding for CP47 and CP43, respectively) were inactivated together with the psaAB operon (coding for the photosystem I (PS I) core complex) and the apcE gene (coding for the phycobilisome anchor protein). Lack of the CP43 protein led to a significant decrease of the D1, D2, and CP47 proteins and a decrease in the 77 K fluorescence emission peak at 685 nm. In the absence of the CP47 protein, no PS II reaction center assembly was detected and the 77 K fluorescence emission peak at 695 nm was lost. The psbB-/psbC-/PS I-less/apcE- mutant had no assembly of the D1, D2, CP47, and CP43 proteins, had lost the 77 K fluorescence emission peaks at 685 and 695 nm, but retained about 15% of the chlorophyll present in the PS I-less/apcE- background strain. A broad 77 K fluorescence emission band with a maximum at 678 nm was displayed in the PS II-less, PS I-less mutant upon excitation of the remaining chlorophyll. A 678 nm shoulder was observed in the 77 K fluorescence emission spectrum of thylakoids from the psbB-/PS I-less/apcE- mutant, which still contains CP43 but no PS II reaction center. This shoulder was absent in thylakoids from the psbC-/PS I-less/apcE- mutant, which contain some PS II reaction center complexes. These results are consistent with the chlorophyll associated with the 678 nm emission to serve as peripheral antenna to PS II. The fluorescence emission characteristics of this chlorophyll are different from those of an accessory chlorophyll-binding protein expressed under iron-stress conditions in cyanobacteria. The chlorophyll remaining in the absence of PS II and PS I is indicative of a new chlorophyll-binding protein in cyanobacterial thylakoids.
Chlorophyll↗
Fractionation of Thylakoid Membranes with the Nonionic Detergent Octyl-beta-d-glucopyranoside: RESOLUTION OF CHLOROPHYLL-PROTEIN COMPLEX II INTO TWO CHLOROPHYLL-PROTEIN COMPLEXES.
The detergent octyl-beta-d-glucopyranoside (30 millimolar in 2 millimolar Tris-maleate, pH 7.0) preferentially extracts complexes containing protein and chlorophylls a plus b (CP) from spinach, leaving a residue highly enriched in CP I (P700-chlorophyll a protein). Use of the detergent results in a relatively gentle extraction since little free chlorophyll is formed and since sodium dodecyl sulfate-gel electrophoresis (on 10% acrylamide) of the extract also reveals the presence of two minor chlorophyll a complexes (apparent molecular weight, 47,000 and 43,000) instead of the usual single complex. The major complex preserved is CP 64, a chlorophyll a/b complex (apparent molecular weight, 64,000) which is an oligomer of another chlorophyll a/b complex, CP 27, the light-harvesting complex (apparent molecular weight, 27,000). Dissociation of each complex reveals two polypeptides (molecular weight, 32,000 and 28,000) and limited proteolysis confirms that those of CP 64 have the same structure as those of CP 27. An additional chlorophyll a/b complex (apparent molecular weight, 29,000) is clearly separable from CP 27, and differs from it and CP 64 in having a higher chlorophyll a/b ratio and a single polypeptide (molecular weight, 29,000) which differs structurally from those of the other complexes.
Journal Article↗
The electrical and spectroscopic properties of planar asymmetrical membranes incorporating chlorophyll a and plastoquinone-9. Model of incorporation of chlorophyll a and plastoquinone-9.
We have studied the incorporation of chlorophyll a and plastoquinone-9 in Montal-Mueller membranes. In particular, we have been interested by the influence of both the lipid : chlorophyll a ratio and the asymmetry of incorporation of the constituents on the electrical and fluorescence spectroscopic properties of the planar membranes built up from these constituents. The phospholipid matrix was made from phosphatidylethanolamine and phosphatidylserine. The monitoring of the fluorescence spectral properties of chlorophyll a incorporated in various concentrations leads to the conclusion that chlorophyll a is incorporated in the bilayers in monomeric form inside microdomains. It is shown that chlorophyll a is positioned in these microdomains in such a way that the porphyric ring is interacting with the polar head of the lipid molecules where the interface polarity shows a dielectric constant varying between 25 and 35. The phytyl chain is embedded in the bilayer core, serving as an anchor, running parallel to the aliphatic chains of the phospholipids. We have also monitored the position of the plastoquinone-9 molecules within the bilayer. We found that plastoquinone-9 is incorporated in the center plane of the bilayer, increasing the thickness of the bilayer. This result confirms evidence, gathered in the literature from monolayer and differential scanning calorimetry studies, that long chain quinones and especially plastoquinone-9 are embedded deeply within the hydrophobic core of the bilayer. We also show that when chlorophyll a and plastoquinone-9 are present together in the bilayer, the quinolic ring of the plastoquinone-9 molecule positions itself in the free volume created by the bulky porphyric ring of a chlorophyll a molecule.
Chemical Phenomena↗
Chlorophyll levels in the pigment-binding proteins of photosystem II. A study based on the chlorophyll to cytochrome ratio in different photosystem II preparations.
The chlorophyll levels in pigment proteins of photosystem II were investigated by using photosystem II preparations with different levels of complexity. Based on the assumption that there is 1 cytochrome b559 per reaction centre it has been found that oxygen-evolving complexes containing CP26 and CP29 bind 42 chlorophyll molecules. When CP26 and CP29 are stripped away, the resulting PSII cores bind 30 chlorophyll molecules while CP43-less cores bind approximately 18 chlorophylls. It is therefore concluded that CP47 and CP43 bind 9-12 molecules of chlorophyll a and the D1/D2 complex binds 6 chlorophylls. Taken together CP26 and CP29 bind about 12 chlorophyll molecules.
Chlorophyll↗
Regulation of light-harvesting chlorophyll-binding protein mRNA accumulation in Chlamydomonas reinhardi. Possible involvement of chlorophyll synthesis precursors.
Light induction of light-harvesting chlorophyll a/b-binding protein (LHCP) mRNA accumulation was studied in light-dark synchronized cultures of Chlamydomonas reinhardi. LHCP mRNA accumulation was prevented by the chlorophyll-synthesis inhibitor alpha,alpha-dipyridyl which blocks late steps in the chlorophyll biosynthetic pathway and leads to the accumulation of the porphyrin intermediate magnesium protoporphyrin methyl ester. LHCP mRNA accumulated normally, however, when chlorophyll synthesis was blocked by inhibitors such as hemin and levulinic acid which interfere with early steps in the chlorophyll biosynthesis pathway prior to the formation of magnesium protoporphyrin methyl ester. Similar effects were observed in the light induction of LHCP mRNA levels in protoporphyrin IX-accumulating mutants, brc-1 and brs-1. These mutants have low levels of LHCP mRNA when grown under heterotrophic conditions in the dark where they accumulate protoporphyrin IX. However, LHCP mRNA is light-induced in brc-1 which synthesizes chlorophyll in the light and presumably consumes porphyrin intermediates in doing so. These results suggest that the chlorophyll-synthesis intermediates, magnesium protoporphyrin methyl ester and its immediate precursors, inhibit by a feedback mechanism the light induction of LHCP mRNA accumulation. Low magnesium protoporphyrin methyl ester levels permit the light-induced accumulation of LHCP mRNA, whereas high magnesium protoporphyrin methyl ester levels destabilize LHCP mRNA regardless of the illumination conditions. Preliminary experiments show that LHCP mRNA accumulation in C. reinhardi is stimulated by blue light, and not by red light which stimulates LHCP mRNA accumulation in higher plants.
2,2'-Dipyridyl↗
Involvement of chlorophyllase in chlorophyll metabolism in olive varieties with high and low chlorophyll content.
Olive fruits of the Arbequina variety are differentiated from those of Hojiblanca and Picual by the differing presence of 132-OH-chlorophyll a and of dephytylated chlorophyll derivatives during the life cycle of the fruit. During the fruit growth stage, which coincides with chlorophyll synthesis, chlorophyllase (EC: 3.1.1.14) is present in the three varieties but only yields chlorophyllides in Arbequina. The presence of oxidized catabolites of chlorophyll a in fruits of the Arbequina variety during this same period confirms the activity of oxidative enzyme systems. The low synthesis of chlorophylls in the fruits of the Arbequina variety is associated with the fact that, during the natural biosynthetic turnover, the catabolic pathway is more potentiated than the anabolic one. In the ripening phase, in the Hojiblanca and Picual fruits, chlorophyllase activity was measured but the absence of chlorophyllides showed that this enzyme remains latent and that oxidative enzymes are the ones taking part in the chlorophyll disappearance. In the Arbequina variety, both chlorophyllase and oxidative enzymes are responsible for the chlorophyll degradation.
Journal Article↗
Two-photon excited fluorescence from higher electronic states of chlorophylls in photosynthetic antenna complexes: a new approach to detect strong excitonic chlorophyll a/b coupling.
Stepwise two-photon excitation of chlorophyll a and b in the higher plant main light-harvesting complex (LHC II) and the minor complex CP29 (as well as in organic solution) with 100-fs pulses in the Q(y) region results in a weak blue fluorescence. The dependence of the spectral shape of the blue fluorescence on excitation wavelength offers a new approach to elucidate the long-standing problem of the origin of spectral "chlorophyll forms" in pigment-protein complexes, in particular the characterization of chlorophyll a/b-heterodimers. As a first result we present evidence for the existence of strong chlorophyll a/b-interactions (excitonically coupled transitions at 650 and 680 nm) in LHC II at ambient temperature. In comparison with LHC II, the experiments with CP29 provide further evidence that the lowest energy chlorophyll a transition (at approximately 680 nm) is not excitonically coupled to chlorophyll b.
Bacterial Proteins↗
Mutation of chlorophyll ligands in the chlorophyll-binding CP47 protein as studied in a Synechocystis sp. PCC 6803 photosystem I-less background.
Site-directed mutations have been introduced to replace conserved histidine residues in the chlorophyll-binding protein CP47 of photosystem II (PS II) in a PS I-less/apcE-background strain of the cyanobacterium Synechocystis sp. PCC 6803. In thylakoids isolated from such a system, the degree of loss of the 695-nm fluorescence emission maximum at 77 K compared to that at 685 nm generally was consistent with the decrease in oxygen evolution rates measured at saturating light intensity. Taking into account that in the absence of CP47 and PS I some chlorophyll remains detectable in cells, the relative 695-nm fluorescence emission and the rate of oxygen evolution also correlate with the relative amount of chlorophyll per cell and with the number of PS II reaction centers on a chlorophyll basis. Interestingly, the 77 K fluorescence excitation spectra monitoring 695-nm emission of thylakoids from the CP47 His-to-Tyr mutants in a photosystem I-less/apcE-background showed increases in the 413- and 531-nm absorption regions, compared to spectra of thylakoids from the background strain. These wavelengths coincide with absorption maxima of pheophytin. No increase in the 531-nm excitation band was observed in thylakoids from mutants lacking PS II or with a His-to-Asn mutation. These results are interpreted to indicate that replacement of conserved histidine residues by tyrosine in CP47 leads to the loss of Mg2+ from chlorophyll, resulting in the formation of pheophytin, or to the binding of pheophytin (rather than chlorophyll) at a particular pigment-binding site of CP47 during biogenesis and assembly of the protein. It was observed that the light-harvesting efficiency of CP47 His mutants was lower judging from the light intensity dependence of electron transport and analysis of fluorescence decay kinetics. This suggests that the presence of pheophytin in the antenna decreases antenna efficiency.
Chlorophyll↗
Properties of protein-chlorophyll complexes from pea (Pisum sativum L.) leaves. The organization of chlorophyll.
Chlorophyll-protein-detergent complexes were prepared from pea chloroplasts by using sodium dodecylbenzenesulphonate and polyacrylamide-gel electrophoresis. Circular-dichroism spectra showed that complex CPI has a dimeric arrangement of chlorophyll a, with additional weaker interactions. Ellipticities were determined for both complexes and for purified chlorophylls in solution, and it is argued that the circular dichroism of complex CPII is derived from chlorophyll-protein interaction rather than from interaction between chlorophylls a and b. The detergent could be removed from the complexes by using urea and gel filtration, leaving the chlorophyll-protein in solution, although in each case a diminished ellipticity indicated some loss of organization. Three-peaked circular-dichroism spectra of chloroplast fragments before and after addition of detergent were compared with a curve obtained by summing graphically the spectra of complexes CPI, CPII and the free-pigment fraction. There was good correspondence at 650 nm, and the longer-wavelength peaks agreed in form and magnitude, but with discrepancies in position. It was concluded that complexes CPI and CPII pre-exist in the original material, but that there is an environmental effect which is destroyed when the complexes are extracted.
Benzenesulfonates↗
Polypeptides belonging to each of the three major chlorophyll a + b protein complexes are present in a chlorophyll-b-less barley mutant.
Polypeptides of the three major chlorophyll a + b protein complexes were detected in a chlorophyll-b-less barley mutant (chlorina f2) using immunological techniques. Antibodies to CP Ia, a photosystem I complex containing both the reaction center (CP I) and the chlorophyll a + b antenna (LHCI), detected substantial amounts of LHCI polypeptides in mutant thylakoids. Some polypeptides of the two photosystem-II-associated chlorophyll a + b complexes, CP 29 and LHCII, were also detected using antibodies raised against these complexes. The CP 29 apoprotein and the minor 25-kDa polypeptide of LHCII were present in amounts that could be seen by Coomassie blue staining. In contrast, the two major polypeptides of LHCII were greatly diminished in amount, and one of them may be completely absent. These data suggest that the absence of chlorophyll b may have differing effects on the synthesis, processing or turnover of the various chlorophyll a + b binding polypeptides. They also show that these polypeptides can be inserted into thylakoids in the absence of Chl b, and that significant amounts of some of them are accumulated in the mutant thylakoids.
Chlorophyll↗
Biosynthesis of chlorophyll b and the chlorophyll cycle.
Recent progress in the knowledge of chlorophyll b biosynthesis from chlorophyllide a and reduction of chlorophyll b to chlorophyll a is described. The minireview includes a description of the enzymes involved in these reactions and, where appropriate, of the genes encoding these enzymes. The possible physiological role of the mutual transformation of chlorophylls a and b (chlorophyll cycle) and the evolution of chlorophyll b formation are discussed.
Journal Article↗
Higher plant chloroplasts: Evidence that all the chlorophyll exists as chlorophyll-protein complexes.
By using the polyacrylamide gel electrophoresis system described in this report, it was possible to fractionate all the photosynthetic pigments of maize (Zea mays L.) thylakoids into chlorophyll-protein complexes with negligible formation of free or detergent-complexed chlorophyll. Identical sodium dodecyl sulfate extracts of thylakoids have previously resulted in up to 50% of the chlorophyll migrating as free chlorophyll after electrophoresis. The major difference from previous gel electrophoresis systems is the replacement of sodium dodecyl sulfate in the electrophoresis buffer by Deriphat 160 (disodium N-lauryl-beta-iminodipropionate), a zwitterionic detergent. The results suggest that: (i) no significant amount of free chlorophyll exists in the chloroplast thylakoid membranes in vivo, and (ii) most of the free pigment seen previously on gels was generated during the electrophoresis and was not a result of the solubilization technique. Additionally, the new chlorophyll-protein complexes resolved appear to have different characteristics (pigment content and size) that those observed in former systems.
Journal Article↗