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At least 91 records · Page 5Linked to original sources
PubMed1988

Hierarchical Response of Light Harvesting Chlorophyll-Proteins in a Light-Sensitive Chlorophyll b-Deficient Mutant of Maize.

The light-sensitive chlorophyll b (Chl b)-deficient oil yellow-yellow green (OY-YG) mutant of maize (Zea mays) grown under conditions of high light exhibits differential reductions in the accumulation of the three major Chl b-containing antenna complexes and characteristic changes in thylakoid architecture. When observed by freeze-fracture electron microscopy, the most notable changes in the OY-YG thylakoid structure are: (a) a major reduction in the number of 8 nanometer particles of the protoplasmic fracture face of stacked membrane regions (PFs) paralleled by a 60% reduction in the chlorophyll-proteins (CP) associated with the peripheral light harvesting complex (LHCII) for photosystem II (PSII) and which give rise to the LHCII oligomer/monomer (CPII(*)/CPII) bands on mildly dissociated green gels; (b) a sizable decrease in the proportion of 11 to 13 nanometer particles of the protoplasmic fracture face of unstacked membrane regions (PFu) that parallels the loss of light harvesting complex I (LHCI) antennae from photosystem I (PSI) centers and a 40% reduction of the band containing CP1 and LHCI (CPI(*)) on mildly dissociating green gels; (c) an unchanged or slightly increased average size of particles of the exoplasmic fracture face of stacked (or appressed) membrane regions (EFs) along with a relative increase in CP29, the postulated bound LHC of PSII, and of CP47 and CP43, PSII core antenna complexes. This latter result sets the OY-YG mutant apart from all other Chl b-deficient mutants studied to date, all of which possess EFs particles that are substantially reduced in size. Based on these findings, we postulate that the bound LHCII associated with EFs particles consists mostly of CP29 chlorophyll proteins and very little, if any, CPII(*)/CPII chlorophyll proteins. Indeed, the CPII(*)/CPII chlorophyll proteins may be exclusively associated with the ;peripheral' LHCII units that give rise to 8 nanometer PF particles. The differential effect of the Chl b deficiency on the accumulation of the three main antenna complexes (CPII(*)/CPII>CPI(*)>CP29) suggests, furthermore, that there is a hierarchy among Chl b-binding proteins, and that this hierarchy might be an integral part of long-term photoregulation mediating Chl b partitioning in the chloroplast.

Journal Article↗
PubMed1993

Conversion of chlorophyll b to chlorophyll a by isolated cucumber etioplasts.

Chlorophyllide b was converted to chlorophyll a when incubated with cucumber etioplasts in the presence of phytol, ATP, and MgCl2. Chlorophyll a was identified by retention time on HPLC, absorption, fluorescence, and excitation spectra. It is suggested that the interconversion of chlorophyll a and b plays a significant role in the establishment of the required chlorophyll a/b ratio during the adaptation of leaves to high and low light conditions.

Chlorophyll↗
PubMed2000

Time-Resolved fluorescence studies on the internal motion of chlorophyll a of light-harvesting chlorophyll a/b-protein complex in lipid membranes.

By analyzing the steady state and time-resolved fluorescence anisotropy, the internal motions of chlorophyll a of light-harvesting chlorophyll a/b-protein complex (LHCII) were characterized in a dimyristoylphosphatidylcholine (DMPC) liposome. Corresponding to the thermotropic phase of the membrane, chlorophyll a showed an unique internal motion in LHCII. At the gel phase, two motional components, one fast and the other slow, were observed, which would originate in the heterogeneity of the mutual orientation and the binding site of the chlorophyll a in LHCII. Interestingly, the faster motion was suppressed and only the slower segmental rotation with the larger motional amplitude was allowed on the phase transition to a liquid crystalline phase.

Animals↗
PubMed1997

[Syntheses and spectra of Mn(III)-chlorophyll-a and Mn(II)-chlorophyll-a].

Manganese(III)-chlorophyll-a [Mn(III)-Chl-a] was synthesized by the reaction of pheophytin-a and manganese(II) acetate and separated by HPCL. Manganese(II)-chlorophyll-a [Mn(II)-Chl-a] was acquired from Mn(III)-chl-a reduced by sodium hydrosulfite (Na2S2O4) in acetone-water. Because Mn(II)-Chl-a is oxidized very easily in the air, Mn (II)-Chl-a was kept under a nitrogen atmosphere and reductant during the spectroscopic measurements. Elemental analysis, absorption and FT-IR spectra proved that the metal Mn-substituted Mg of chlorophyll-a has been successfully performed and possible structure of new complexes was also given. Their formulae are [Mn(II) (chlorophyll-a)] and [Mn(III) (chlorphyll-a) (CH3COO)-(H2O)] respectively.

Chlorophyll↗
PubMed1983

Supramolecular structure of chlorophyll-protein complexes in relation to the chlorophyll a fluorescence of chloroplasts at room or liquid nitrogen temperature.

To investigate further the possibility that changes in the organization of the thylakoid pigment-protein complexes are monitored by the chlorophyll a fluorescence yield changes, or by changes in the F685/F730 ratio in the 77 degrees K fluorescence, as earlier proposed (A. Castorinis, G. Akoyunoglou, and J.H. Argyroudi-Akoyunoglou (1982) Photobiochem. Photobiophys. 4, 283-291; J.H. Argyroudi-Akoyunoglou, A. Castorinis, and G. Akoyunoglou (1982) Photobiochem. Photobiophys. 4, 201-210), the effect of pH, Cd2+ or Zn2+ addition, and trypsinization on all parameters was studied. We found that (a) the pH of the medium affects the ratio of oligomeric to monomeric structures of the complexes (monomers predominate at low pH), as well as the ratio F685/F730 of thylakoids or of the isolated CPIa complex (the F685/F730 ratio is high at low pH, and low at high). (b) Zn2+ or Cd2+ addition to thylakoids, suspended in Tricine (N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine), has no effect on the chlorophyll a fluorescence yield nor on the F685/F730 ratio at 77 degrees K; similarly, no effect can be noticed on the F685/F730 ratio at 77 degrees K of the isolated CPIa complex. These cations, contrary to Mg2+, do not affect the oligomer to monomer dissociation, but they instead reverse the cation effect and enhance the oligomeric structures. (c) Trypsinized thylakoids in Tricine do not show the Mg2+ effect on the chlorophyll a fluorescence yield, have a reduced F730/F685 ratio at 77 degrees K, and are deficient in the CPIa complex, which is mainly responsible for the F685/F730 ratio changes in the presence of cations. The results support the proposal that cation- or pH-induced changes in the chlorophyll a fluorescence yield at room temperature, or in the F685/F730 ratio at 77 degrees K, are irrelevant to the excitation energy distribution between the two photosystems. They instead seem to reflect changes in the organization of the supramolecular structure of the pigment-protein complexes in the photosystem I and photosystem II units.

Biopolymers↗
PubMed1980

Macromolecular organization of chlorophyll a in aggregated chlorophyll a/b protein complex as shown by circular dichroism at room and cryogenic temperatures.

This report concerns the circular dichroic (CD) signal of intact chloroplasts of higher plants. The CD spectra of chloroplasts are compared with the aggregated form of the light-harvesting chlorophyll a/b complex at 25 degrees C and -250 degrees C. The light-harvesting chlorophyll aggregate has a CD of magnitude equal to or greater than chloroplasts, but of opposite sign, and it is not related to the CD of the unaggregated form, and hence its arrangement is an artefact compared to the arrangement in the chloroplast. We suggest that this preparation, which has pseudo-lamellar structure, is a clear example of a large CD signal being generated by macromolecular association. The asymmetry of organization in the chloroplast has an opposite sense to that of the aggregate, but affects only chlorophyll a, not chlorophyll b.

Cell Membrane↗
PubMed2002

Chlorophyll breakdown in spinach: on the structure of five nonfluorescent chlorophyll catabolites.

In extracts of senescent leaves of spinach (Spinacia oleracea), five colourless compounds with UV/Vis-characteristics of nonfluorescent chlorophyll catabolites (NCCs) were detected and tentatively named So-NCCs. The most abundant polar NCC in the leaves of this vegetable, So-NCC-2, had been isolated earlier and its constitution was determined by spectroscopic means. The catabolite So-NCC-2 was found to be an epimer of a polar NCC from barley (Hordeum vulgare), the first non-green chlorophyll catabolite from a higher plant to be structurally analyzed. Here, we report on the isolation of four additional So-NCCs from the extracts of senescent leaves of Sp. oleracea by two- (or multi-)stage chromatographic purification and on their structural characterization. The constitution of So-NCC-3 could be determined by spectroscopic analysis in combination with chemical correlation with a known NCC from Cercidiphyllum japonicum (Cj-NCC): So-NCC-3 was identified as the hydrolysis product of the methyl ester function of Cj-NCC. The less polar catabolite So-NCC-4 could be directly identified with Cj-NCC. Two further So-NCCs, So-NCC-1 and So-NCC-5, were detected only in trace amounts. Five structurally related nonfluorescent chlorophyll catabolites (So-NCCs) are thus present in senescent leaves of spinach. The structures of this set of So-NCCs indicate several peripheral refunctionalization reactions and inform on the late catabolic transformations during leaf senescence. The transformation of the tetrapyrrolic skeleton in chlorophyll catabolism in spinach and in C. japonicum is revealed to exhibit a common stereochemical pattern.

Journal Article↗
PubMed1983

Organization of Chlorophyll a in the Light-Harvesting Chlorophyll a/b Protein Complex as Shown by Circular Dichroism : Liquid Crystal-Like Domains.

The development of thylakoid stacking, accumulation of the light-harvesting chlorophyll a/b protein complex (LHCP), and the changes of circular dichroism (CD) which reflect the organization of chlorophyll molecules in greening thylakoids of bean Phaseolus vulgaris cv Red Kidney leaves were investigated.Chloroplasts formed under intermittent light contained large double sheets of membrane with extensive appression in addition to separate lamellae. Thylakoids of such chloroplasts were devoid of LHCP and exhibited a relatively small CD in the chlorophyll absorption region. Upon continuous illumination, the rearrangement of membranes to characteristic grana and the accumulation of the LHCP was accompanied by the gradual appearance of the very intense CD signal with peaks at 682 to 684 (+) and 665 to 672 nanometers (-). The magnitude of differential absorption was approximately 100 times larger than that of the chlorophyll a in solution. This suggests a superhelical liquid crystal-like organization for LHCP, a texture which can be altered by changes of the electric field in the photosynthetic membranes.

Journal Article↗
PubMed1985

Chloramphenicol stimulation of light harvesting chlorophyll protein complex accumulation in a chlorophyll B deficient wheat mutant.

As compared with normal wheat leaves, the chlorina wheat mutant, designated CD3, has a high chlorophyll a/b ratio and a deficiency in the light harvesting chlorophyll protein (LHCP) complex. Applications of 200 micrograms per milliliter of d-threo-chloramphenicol to etiolated seedlings decreased the chlorophyll a/b ratio and increased the accumulation of the 27 kilodalton LHCP polypeptide and the LHCP complex in thylakoids of the mutant during greening. These data led to the suggestion that a protein encoded in chloroplast genes impaired either transcriptional, translational, or posttranslational events in CD3 wheat limiting the accumulation of the LHCP complex. The LHCP complex which accumulated in chloramphenicol treated wheat appeared functional even though chlorophyll protein complex accumulations were altered greatly in the wheat thylakoids. LHCP polypeptides were phosphorylated by action of a membrane protein kinase but yet photosystem II electron transport was impaired. The chloramphenicol treatment increased the photosystem I/photosystem II ratio of electron transport and the fluorescence emission ratio at 740 to 686 nanometers relative to those of untreated wheat. Chloramphenicol prevented development of normal granal thylakoids in normal wheat chloroplasts but not in those of the CD3 mutant. Elongated stacked thylakoids were observed in normal wheat. Net-like membranes and vesicles were noted in the stroma of chloroplasts from treated mutant seedlings.

Journal Article↗
PubMed2002

Monolayers and multilayers of chlorophyll [correction of chlorophyl] a on a mercury electrode.

A novel experimental technique used to investigate chlorophyll films on a hanging mercury drop electrode is described. Two different procedures are employed to prepare self-assembled chlorophyll monolayers and multilayers on the mercury electrode. Upon illuminating the chlorophyll a (Chl)-coated mercury electrode with an appropriate light source, the photocurrents generated by the Chl aggregates are measured under short-circuit conditions in the absence of photoartefacts. The preliminary results obtained by this novel technique are presented.

Chlorophyll↗
PubMed2005

Photochemical reactions of chlorophyll in dehydrated photosystem II: two chlorophyll forms (680 and 700 nm).

Lichens and phototolerant poikilohydric mosses differ from spinach leaves, fern fronds or photosensitive mosses in that they show strongly decreased Fo chlorophyll fluorescence after drying. This desiccation-induced fluorescence loss is rapidly reversible under rehydration. Fluorescence emission from Photosystem II at 685 nm was decreased more strongly by dehydration than 720 nm emission. Reaction centers of Photosystem II lose activity on dehydration and regain it on hydration. Heating of desiccated lichens increased Fo chlorophyll fluorescence. The activation energy for the reversible part of the temperature-dependent fluorescence increase was 0.045 eV, which corresponds to the energy difference between the 680 and 697 nm absorption bands. In desiccated chlorolichens such as Parmelia sulcata, heating induces the appearance of positive variable fluorescence related to the reversible reduction of QA due to overcoming the energy barrier. This is interpreted to provide information on the mechanism of photoprotection: energy is dissipated by changing Chl680 or P680 into a chlorophyll form, which absorbs at 700 nm and emits light at 720 nm (Chl-720 or P680(700)) with a low quantum yield. Dissipation of light energy in this trap is activated by desiccation.

Bryophyta↗
PubMed2005

Estimation of chlorophyll content and daily primary production of the major algal groups by means of multiwavelength-excitation PAM chlorophyll fluorometry: performance and methodological limits.

The performance and methodological limits of the Phyto-PAM chlorophyll fluorometer were investigated with laboratory grown algae cultures and natural phytoplankton from the rivers Saar and Saale. The Phyto-PAM is a 4-wavelength chlorophyll fluorometer with the functional combination of chlorophyll (Chl) estimation and assessment of photosynthetic activity, both differentiated into the main algal groups. The reliability of fluorescence-based Chl estimation strongly depends on the group specific calibration of the instrument and the resulting chlorophyll/fluorescence (Chl/F) ratios in reference algal cultures. A very high reliability of the Chl estimation was obtained in the case of constant Chl/F-ratios. Algae grown at different light intensities showed marked differences in Chl/F-ratios, reflecting differences in pigment composition and Chl a specific absorption (a*). When the Phyto-PAM was calibrated with laboratory grown diatoms, the Chl a in river grown diatoms was underestimated, due a lower content of accessory pigments and stronger pigment packaging. While this aspect presently limits the application of PAM fluorometry in limnology, this limitation may be overcome by future technical progress in the detection of dynamic changes in Chl/F-ratio via fluorescence-based measurements of the functional PS II absorption cross-section. Practically identical Chl/F-ratios were found for the diatom-dominated waters of the rivers Saar and Saale, suggesting that the same instrument calibration parameters may be applied for hydrographically similar surface waters. For this particular case, despite of the present methodological limitations, the potential of PAM fluorometry in limnology could be demonstrated. Light response curves were measured to estimate primary production with a spectrally resolved model in daily courses at two sampling sites. Fluorescence based primary production was closely correlated with measured oxygen evolution rates until midday. In the afternoon, at the water surface the fluorescence approach gave higher rates than the measured oxygen evolution. Possible explanations for the observed differences are discussed.

Chlorophyll↗
PubMed1990

Chlorophyll-free chromoplasts from daffodil contain most of the enzymes for chlorophyll synthesis in a highly active form.

Chromoplasts isolated from chlorophyll-free daffodil flowers utilize in vitro delta-aminolevulinic acid (ALA) as precursor for the synthesis of large amounts of at least nine different products. Their identification as intermediates of the chlorophyll biosynthetic pathway demonstrates the presence of the majority of the respective enzymes in this nongreen plastid preparation. Porphobilinogen synthase was investigated more closely and found to be similar in its properties to the corresponding enzyme from other plastid sources. Protoporphyrin IX was also accepted as a substrate by chromoplast homogenate; here, as in the case of ALA as a substrate, Mg-protoporphyrin IX monomethyl ester was the last product formed. Formation of the isocyclic chlorophyll ring was not observed.

Aminolevulinic Acid↗
PubMed1987

Resonance Raman spectra of chlorophylls dissolved in liquid crystal matrices. I. The interaction between chlorophylls and a liquid crystalline MBBA + EBBA mixture.

The resonance Raman (RR) spectra of chlorophyll (Chl) a, Chl b and pheophytin a dissolved in a liquid-crystalline MBBA + EBBA mixture were measured. The RR frequencies of chlorophylls in the liquid crystal (LC) are compared with those of solutions of various chlorophyll monomers and aggregates taken from the literature. It is concluded that Chl a and Chl b in LC exist largely as the solvated monomers, even at high concentration. The magnesium atoms in both Chl a and Chl b are pentacoordinated.

Benzylidene Compounds↗
PubMed1994

Chlorophyll synthetase cannot synthesize chlorophyll a'.

Chlorophyll synthetase catalyzes the last step of chlorophyll biosynthesis, namely prenylation (esterification) of chlorophyllide with phytyl diphosphate or geranylgeranyl diphosphate. During investigation of various chlorophyllide derivatives as potential substrates we observed lower esterification with increasing percentages of chlorophyllide a' in epimeric mixtures of chlorophyllides a and a'. To avoid epimerization during esterification, we studied the reaction in detail with model compounds [zinc-13(2)(R)-methoxy-pheophorbide a and zinc-13(2)(S)-methoxy-pheophorbide a, zinc-13(2)(R)-methoxy-pyropheophorbide a and zinc-chlorine6-13(1), 15(2)-dimethylester]. We conclude that compounds which have the 13(2)-carbomethoxy group at the same side of the macrocycle as the propionic side chain of ring D are neither substrates nor competitive inhibitors. Only compounds having the 13(2)-carbomethoxy group at the opposite site are substrates for the enzyme. Naturally occurring chlorophyll a' must be formed by epimerization after esterification.

Carbon-Oxygen Ligases↗
PubMed1991

Integration of a chlorophyll-binding protein into Escherichia coli membranes in the absence of chlorophyll.

The mechanism by which a protein integrates posttranslationally into a membrane can involve the composition of the membrane itself, domains within the inserting polypeptide, and a number of associating proteins. Some integral membrane proteins do not accumulate to normal levels when certain pigments are deficient, and this has been interpreted to mean that such proteins may be rapidly degraded when not in a correct complex. Alternatively, pigments could facilitate the movement of some proteins from an aqueous to a lipid environment. To determine whether chlorophyll is absolutely required for the membrane integration of the light-harvesting chlorophyll-binding protein (LHCP) of chloroplast thylakoid membranes, we have expressed LHCP in Escherichia coli that lacks photosynthetic pigments. LHCP is targeted to the bacterial inner membrane by the addition of a bacterial signal peptide and cannot be extracted from these membranes by NaOH, NaBr, or Na2HCO3 but is extracted by 0.2% Triton X-100. Treatment of isolated right-side-out and inside-out bacterial inner membrane vesicles with trypsin reveals that only the amino terminus of LHCP is exposed on the cytoplasmic face, and the remaining portion of the protein is inaccessible. Treatment of the inside-out vesicles with trypsin followed by alkaline extraction shows that LHCP is intrinsic to the membrane and is not anchored solely by the bacterial signal peptide. Chlorophyll, therefore, is not required for LHCP to integrate into a membrane, but in the absence of these pigments this process is observed to be inefficient.

Amino Acid Sequence↗
PubMed1980

Dichroism and polarized fluorescence of chlorophyll a, chlorophyll c and bacteriochlorophyll a dissolved in liquid crystals.

Three photosynthetic pigments were studied: chlorophyll a, chlorophyll c and bacteriochlorcphyll a in nematic liquid crystal matrixes. The polarized absorption and fluorescence spectra as a function of the electric field have been measured. From the polarized components of the absorption A( parallel) and A( perpendicular) of the pigments in liquid crystals two reduced components A(x) and A(y) are calculated (x and y are the direction of the axis which is going through the second, fourth pyrrol rings, and the first, third rings, respectively). From these results the orientation of chlorophylls in liquid crystals and the configuration of the transition moments in the skeleton of the pigment molecules were determined.

Journal Article↗
PubMed2002

Quest for minor but key chlorophyll molecules in photosynthetic reaction centers - unusual pigment composition in the reaction centers of the chlorophyll d-dominated cyanobacterium Acaryochloris marina.

A short overview, based on our own findings, is given of the minor pigments that function as key components in photosynthesis. Recently, we found the presence of chlorophyll a, chlorophyll d' and pheophytin a as minor pigments in the chlorophyll d-dominated cyanobacterium Acaryochloris marina.

Journal Article↗