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PubMedDate not supplied

[Studies of sorption and interaction of chlorophyll and chlorophyllase on methylaerosil].

The article deals with the possibility of chlorophyll and chlorophyllase immobilization on methylaerosil and also with the effect of this carrier on the enzyme-substrate interaction. Chlorophyll and chlorophyllase are shown to be able to hydrophorbic interaction. It is established that the ultimate saturation of methylaerosil with chlorophyll is 16.1 mg per 100 mg of the carrier. The chlorophyllase reaction is the most active under conditions when the enzyme and substrate are in soluble states. The hydropholic binding of chlorophyll with methylaerosil decreases the intensity of its hydrolysis for the period of reaction and the preliminary immobilization of chlorophyllase on methylaerosil inhibits the reaction to a still greater extent. This evidences for the significance of the reaction system organization for interaction of chlorophyllase with chlorophyll.

Carboxylic Ester Hydrolases↗
PubMed1983

Effect of temperature on chlorophyll stability of some subaerial blue-green algae.

Chlorophyll stability index of eight subaerial blue-green algal species, collected from their natural habitats, i.e., bark of trees, soil and roof-tops and from cultures, has been determined. The algae from natural habitats showed greater chlorophyll stability compared to those algae from cultures. Among the natural algae, high chlorophyll stability was observed in the algae inhabiting adverse habitats. A slight modification in the method of Murty and Majumder (1962) for determination of chlorophyll stability index has been made. Here the total percentage loss in the amount of Chl alpha of heated sample in relation to its unheated sample has been considered as chlorophyll stability index.

Chlorophyll↗
PubMed1982

Protein synthesis by isolated Acetabularia chloroplasts. Synthesis of the two minor chlorophyll a complexes in vitro.

Isolated chloroplasts of Acetabularia incorporate radioactive amino acids into more than 30 polypeptides in the light, including the apoprotein of the P700-chlorophyll a protein complex, the reaction centre core of photosystem I [Biochim. Biophys. Acta, 609. 107-120 (1980)]. In this paper it is shown that the apoproteins of the two minor chlorophyll a complexes, thought to be part of photosystem II reaction centre core, are also synthesized by isolated chloroplasts. Furthermore, they are integrated correctly into the thylakoid membrane in the absence of any cytoplasmic contribution, such that they can be isolated as chlorophyll-protein complexes indistinguishable from those already in the membrane. In contrast, the minor chlorophyll a + b complex 'CP 29' [Camm, E. L. and Green, B. R. (1980) Plant Physiol. 66, 428-432] and its dimers are not synthesized by isolated chloroplasts. In this they resemble the other chlorophyll a + b complex, the light-harvesting complex (LHC). It may be significant that the LHC, which is not essential for photosynthetic activity, is under nuclear control, while the reaction centre polypeptides, cytochrome b559, and cytochrome f, are synthesized on chloroplast ribosomes.

Acetabularia↗
PubMedDate not supplied

[Photophysics of complex formations between chlorophyll a and its analogs with pi acceptors].

Efficient quenching of fluorescence was shown to proceed in the complexes of chlorophyll a and its analogs with tetracyanochinodimethane (TCD), 1,3,5-trinitrobenzene (TNB), m-dinitrobenzene (DNB) and n-benzoquinone. In chlorophyll a--TCD and--DNB complexes quenching is characterized by the rate constant approximately greater than 5 x 10(10) s-1, and in chlorophyll a--n-benzoquinone greater approximately than 5 x 10(9) s-1. Possible ways of desactivation of singlet-excited state of chlorophyll a in the complexes with TCD and TNB were analysed. No triplet states of chlorophyll a complexes with TCD and TNB and no cation-radicals were recorded. It is suggested that efficient desactivation of the pigment singlet-excited state may be explained by a reversible phototransfer of the electron.

Benzoquinones↗
PubMed1980

Induced mutagenesis in Vicia faba L. 1 Chlorophyll mutations induced by gamma rays, ethyl methane sulphonate and hydrazine.

The seeds of Vicia faba L. (2n = 12) having a moisture content of 9.06% were given individual and combined treatments of gamma rays (5 kR), ethyl methane sulphonate (0.25% and 0.50%, 6 h) and hydrazine (0.25% and 0.50%, 6 h). Chlorophyll mutations were scored in the M2-generation as mutants per 100 M2 plants. The mutation frequency was highest for xantha and lowest for striata. The frequency of chlorophyll mutations was higher due to chemicals than due to gamma rays at the available levels of treatments. Quantitative estimation of chlorophyll pigments was also made in different kinds of chlorophyll mutants and the chlorophyll content was in the following decreasing order: viridoalba > chlorina > xanthoalba > striata > viridis > alboxantha > xantha > albino. The total leaf area in these mutants was similarly found in the following decreasing order: viridoalba > chlorina > xantha > xanthoalba > alboxantha > viridis > striata > albino.

Chlorophyll↗
PubMed1963

Chlorophyll a appearance in the dark in higher plants: analytical notes.

The increase in the ratio [chlorophyll a]/[chlorophyll b] which occurs in expanding bean leaves in the dark, is a result of chlorophyll a formation with a concomitant loss in chlorophyll b. The analytical methods for assay of these pigments were examined closely and found to be adequate for this purpose when proper safeguards are taken.

Chlorophyll↗
PubMed1996

Gene structure of a chlorophyll a/c-binding protein from a brown alga: presence of an intron and phylogenetic implications.

A Laminaria saccharina genomic library in the phage EMBL 4 was used to isolate and sequence a full-length gene encoding a fucoxanthin-chlorophyll a/c-binding protein. Contrary to diatom homologues, the coding sequence is interrupted by an intron of about 900 bp which is located in the middle of the transit peptide. The deduced amino acid sequence of the mature protein is very similar to those of related proteins from Macrocystis pyrifera (Laminariales) and, to a lesser extent, to those from diatoms and Chrysophyceae. Seven of the eight putative chlorophyll-binding amino acids determined in green plants are also present. Alignments of different sequences related to the light-harvesting proteins (LHC) demonstrate a structural similarity among the three transmembrane helices and suggest a unique ancestral helix preceded by two beta-turns. The beta-turns are conserved in front of the second helices of the chlorophyll a/c proteins more so than in chlorophyll a/b proteins. Phylogenetic trees generated from sequence data indicate that fucoxanthin-chlorophyll-binding proteins diverged prior to the separation of photosystem I and photosystem II LHC genes of green plants. Among the fucoxanthin-containing algae, LHC I or II families could not be distinguished at this time.

Amino Acid Sequence↗
PubMed2002

Folding in vitro of light-harvesting chlorophyll a/b protein is coupled with pigment binding.

The major light-harvesting chlorophyll a/b protein (LHCIIb) of the plant photosynthetic apparatus is able to self-organise in vitro. When the recombinant apoprotein, Lhcb1, is solubilised in the denaturing detergent sodium (or lithium) dodecylsulfate (SDS or LDS) and then mixed with chlorophylls and carotenoids under renaturing conditions, structurally authentic LHCIIb forms. Assembly of functional LHCIIb, as indicated by the establishment of energy transfer between complex-bound chlorophyll molecules, occurs in two apparent kinetic steps with time constants of 10 to 30 seconds and 50 to 300 seconds, depending on the reaction conditions. Here, we use circular dichroism (CD) in the far-UV range to monitor the folding of the LHCIIb apoprotein as it is complexed with pigments. The alpha-helix content in the protein's secondary structure increases in two apparent kinetic steps with time constants similar to those observed for the establishment of chlorophyll energy transfer. When the carotenoid concentration in the reaction mixture is reduced, the time constants of alpha-helix formation increase, as do those for the appearance of chlorophyll energy transfer. This indicates that both processes, pigment assembly and secondary structure formation, are tightly coupled. A substantial amount of alpha-helix is present in dodecylsulfate-solubilised LHCIIb apoprotein and appears to be distributed among various protein domains.

Circular Dichroism↗
PubMed2001

On the nature of the two pathways in chlorophyll formation from protochlorophyllide.

The kinetics of formation of esterified chlorophyll in etiolated barley (Hordeum vulgare L.) leaves after illumination with a single flash was studied. It was found that after partial (14-24%) and after full photoreduction of protochlorophyllide, the same quantity of esterified products appear during the first 5 s after the flash. The rest of formed chlorophyllide was esterified in a slow process during at least 30 min at 15 degrees C. The product of fast esterification can be correlated with 'short-wavelength' chlorophyll, characterized by a fluorescence emission peak at 673-675 nm. This is the only chlorophyll form detectable within 20 s after partial (14%) photoconversion, and it appears at the same time as the shoulder of the chlorophyll(ide) fluorescence after full photoconversion. The main product after full photoconversion shows a fluorescence at 689 nm shifting in darkness within 15 s to 693 nm and then within 30 min to 682 nm (Shibata shift). The slow esterification proceeds with similar kinetics as the Shibata shift. We propose that the fast esterification of only part of total chlorophyllide after full photoconversion of protochlorophyllide in etiolated leaves reflects the restricted capacity of the esterifying system. The slow esterification of the residual chlorophyllide may be time-limited by its release from protochlorophyllide oxidoreductase, by disaggregation of prolamellar bodies and by diffusion of tetraprenyl diphosphates towards chlorophyll synthase.

Journal Article↗
PubMed2001

Does elevated CO2 ameliorate the impact of O3 on chlorophyll content and photosynthesis in potato (Solanum tuberosum)?

This study examined the impact of season-long exposure to elevated carbon dioxide (CO2) and ozone (O3), individually and in combination, on leaf chlorophyll content and gas exchange characteristics in potato (Solanum tuberosum L. cv. Bintje). Plants grown in open-top chambers were exposed to three CO2 (ambient, 550 and 680 µmol mol-1) and two O3 treatments (ambient and elevated; 25 and 65 nmol mol-1, 8 h day-1 means, respectively) between crop emergence and maturity; plants were also grown in unchambered field plots. Non-destructive measurements of chlorophyll content and visible foliar injury were made for all treatments at 2-week intervals between 43 and 95 days after emergence. Gas exchange measurements were made for all except the intermediate 550 µmol mol-1 CO2 treatment. Season-long exposure to elevated O3 under ambient CO2 reduced chlorophyll content and induced extensive visible foliar damage, but had little effect on net assimilation rate or stomatal conductance. Elevated CO2 had no significant effect on chlorophyll content, but greatly reduced the damaging impact of O3 on chlorophyll content and visible foliar damage. Light-saturated assimilation rates for leaves grown under elevated CO2 were consistently lower when measured under either elevated or ambient CO2 than in equivalent leaves grown under ambient CO2. Analysis of CO2 response curves revealed that CO2-saturated assimilation rate, maximum rates of carboxylation and electron transport and respiration decreased with time. CO2-saturated assimilation rate was reduced by elevated O3 during the early stages of the season, while respiration was significantly greater under elevated CO2 as the crop approached maturity. The physiological origins of these responses and their implications for the performance of potato in a changing climate are discussed.

Journal Article↗
PubMed1979

Lithium dodecyl sulfate/polyacrylamide gel electrophoresis of thylakoid membranes at 4 degrees C: Characterizations of two additional chlorophyll a-protein complexes.

Lithium dodecyl sulfate/polyacrylamide gel electrophoresis of Chlamydomonas reinhardtii thylakoid membranes at room temperature gave two chlorophyll-protein complexes, CP I and CP II, as had been reported previously. However, when the electrophoresis was performed at 4 degrees C, there was an increase in the amount of chlorophyll associated with CP I and CP II, and in addition, three other chlorophyll-protein complexes appeared. Two of these complexes, designated CP III and CP IV, were characterized and found to be similar in their compositions. Each complex contains four to five molecules of chlorophyll a, one molecule of beta-carotene, and one polypeptide chain. The apoprotein of CP III is polypeptide 5 (M(r) 50,000) and that of CP IV is polypeptide 6 (M(r) 47,000); the two polypeptides are structurally unrelated. Chlorophyll-protein complexes similar to C. reinhardtii CP III and CP IV were also detected in higher plants (e.g., Pisum sativum). The apoproteins of the higher plant complexes are immunochemically related to those of the C. reinhardtii complexes, as shown by crossed immunoelectrophoresis. Absorption spectra of CP III and CP IV at -196 degrees C revealed a component at 682 nm. This observation, together with the previous results on photosystem II mutants [Chua, N.-H. & Bennoun, P. (1975) Proc. Natl. Acad. Sci. USA 72, 2175-2179], provides indirect evidence that CP III and CP IV may be involved in the primary photochemistry of photosystem II.

Journal Article↗
PubMed1980

Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy.

Self-assembled chlorophyll a and pheophytin a systems in thin solid films have been studied by (252)Cf plasma desorption mass spectrometry (PDMS). The (252)Cf-PDMS spectra of these films show monomer cation and anion molecular ions, ions of molecular aggregates, and positive and negative ion fragmentation patterns arising from the loss of various aliphatic side chains from the chlorin ring. Chlorophyll a films cast from dry carbon tetrachloride solution, in which chlorophyll a is known to occur as the dimer, produced an abundant dimer ion. The highest degree of chlorophyll a self-assembly was observed in chlorophyll a films cast from n-octane solutions. Oligomer ions extending upwards in size to the heptamer were detected in this system.

Journal Article↗
PubMed1988

Electron spin resonance of charge carriers in chlorophyll a/water micelles.

Chlorophyll a/water micelles (P740) prepared in hydrocarbon media have been shown by small-angle neutron scattering to consist of hollow cylinders whose surface is formed of a monolayer of chlorophyll crosslinked by water. The micelles can be reversibly oxidized or reduced to generate highly mobile holes or electrons that undergo rapid, one-dimensional transport along the chains of chlorophyll macrocycles comprising the surface of the micelles. Large pi-pi overlap within the chains facilitates the one-dimensional charge transport and is expected to do the same for energy transport. Structural defects in the micelle surface act as boundaries for charge transport, confining the spins to one-dimensional domains of approximately 200 macrocycles. The one-dimensional transport within the limited domains results in motionally narrowed electron spin resonance lines with some residual inhomogeneous broadening. Although the chlorophyll a incorporated in micelles is more easily oxidized than is monomeric chlorophyll a, it is much more resistant to chemical alteration.

Journal Article↗
PubMed1992

Reversible and irreversible intermediates during photoinhibition of photosystem II: stable reduced QA species promote chlorophyll triplet formation.

Photoinhibition of photosynthesis was studied in isolated photosystem II membranes by using chlorophyll fluorescence and electron paramagnetic resonance (EPR) spectroscopy combined with protein analysis. Under anaerobic conditions four sequentially intermediate steps in the photoinhibitory process were identified and characterized. These intermediates show high dark chlorophyll fluorescence (Foi) with typical decay kinetics (fast, semistable, stable, and nondecaying). The fast-decaying state has no bound QB but possesses a single reduced QA species with a 30-s decay half-time in the dark (QB, second quinone acceptor; QA, first quinone acceptor). In the semistable state, Q-A is stabilized for 2-3 min, most likely by protonation, and gives rise to the Q-A Fe2+ EPR signal in the dark. In the stable state, QA has become double reduced and is stabilized for 0.5-2 hr by protonation and a protein conformational change. The final, nondecaying state is likely to represent centers where QA H2 has left its binding site. The first three photoinhibitory states are reversible in the dark through reestablishment of QA to QB electron transfer. Significantly, illumination at 4 K of anaerobically photoinhibited centers trapped in all but the fast state gives rise to a spinpolarized triplet EPR signal from chlorophyll P680 (primary electron donor). When oxygen is introduced during anaerobic illumination, the light-inducible chlorophyll triplet is lost concomitant with induction of D1 protein degradation. The results are integrated into a model for the photoinhibitory process involving initial loss of bound QB followed by stable reduction and subsequent loss of QA facilitating chlorophyll P680 triplet formation. This in turn mediates light-induced formation of highly reactive and damaging singlet oxygen.

Journal Article↗
PubMed1966

Effects of Light Intensity on Photosynthetic Carboxylative Phase Enzymes and Chlorophyll Synthesis in Greening Leaves of Hordeum vulgare L.

The effects of various light intensities on in vivo increases in activities of phosphoriboisomerase, phosphoribulokinase and ribulose-1, 5-diP carboxylase and on synthesis of chlorophyll were studied in greening leaves of Hordeum vulgare L.Each enzyme was already present in dark-grown plants, but further increases in activities required both a light treatment of the intact plant and a favorable temperature. The amount of enzymatic activity and chlorophyll developed was governed by light intensity.Measured activities of phosphoriboisomerase and ribulose 1,5-diP carboxylase were highly correlated with synthesis of chlorophyll at all intensities studied. Measured activity of phosphoribulokinase was correlated with synthesis of chlorophyll only at saturating or near saturating light intensities. At decreasing light intensities the response curves of this enzyme differed from those of chlorophyll and of phosphoriboisomerase and ribulose-1, 5-diP carboxylase. A lag period of phosphoribulokinase increased with decreasing light intensity. After the lag period a rapid rate of increase occurred which did not level off during 48 hours of illumination. Thus, a different control mechanism may be operative in inducing increased activity of this enzyme.

Journal Article↗
PubMed1971

Chlorophyll synthesis in chlorella: regulation by degree of light limitation of growth.

The degree of light limitation of growth is the primary controlling factor of chlorophyll synthesis during photoautotrophic growth of Chlorella. The chlorophyll content of the cells increases when light is limiting for growth as occurs in dense cultures, or in cultures under low incident light, or when the light is used less efficiently through partial inhibition of photosynthesis by 3-(p-chlorophenyl)-1, 1-dimethylurea. The chlorophyll content decreases when light is not limiting for growth, as occurs in cells in high light intensity and in dilute suspensions. The initial lag in rate of chlorophyll synthesis in a freshly inoculated culture can be attributed to light at first not being growth limiting, and then becoming growth limiting as the cell suspension becomes denser. Continuous culture experiments support the above conclusions by showing that under steady state conditions the chlorophyll content is inversely related to the relative available light.

Journal Article↗
PubMed1971

Chlorophyll, Ribulose-1,5-diphosphate Carboxylase, and Hill Reaction Activity in Developing Leaves of Populus deltoides.

The synthesis of chlorophyll and ribulose diphosphate carboxylase as well as the development of Hill reaction activity were followed in expanding Populus deltoides leaves and related to photosynthetic patterns. Total chlorophyll, which was not correlated with photosynthetic rate in expanding leaves, decreased slightly with age in very young leaves, due to a decrease in chlorophyll b, but then increased linearly. The ratio of chlorophyll a to b, which rose sharply in young leaves, was highly correlated with the onset of net photosynthesis. Hill reaction activity was very low in young leaves and did not increase significantly until leaves were about half expanded. Ribulose diphosphate carboxylase activity increased in a sigmoid fashion with leaf ontogenesis and closely paralleled development of the photosynthetic system. The study demonstrates the importance of chlorophyll a and Calvin cycle enzyme synthesis to photosynthetic development in expanding leaves.

Journal Article↗
PubMed1972

High photosynthetic rate of a chlorophyll mutant of cotton.

In a chlorophyll mutant (virescent) and wild-type cotton (Gossypium hirsutum L.), a number of photosynthetic parameters have been measured and compared with those published for other chlorophyll mutants. (a) The photosynthetic rates at 230 w/m(2) (400-700 nm) from a tungsten lamp were 36.8 mg CO(2) fixed/dm(2).hr (virescent) and 39.5 mg CO(2) fixed/dm(2).hr (wild-type). On a chlorphyll basis, the photosynthetic rates were 36.8 and 12.1 mg CO(2) fixed/mg chl.hr, respectively. (b) The photosynthetic rates at 13 w/m(2) (400-700 nm) from a tungsten source were 7.1 mg CO(2) fixed/dm(2).hr (virescent) and 7.4 mg CO(2) fixed/dm(2).hr (wild-type). On a chlorophyll basis, the photosynthetic rates were 6.0 and 1.4 mg CO(2) fixed/mg chl.hr, respectively. (c) The chlorophyll a/b ratios of the virescent and wild-type leaves were 3.3 and 4.1 (d) The chlorophyll/carotenoid ratios for the virescent and wild-type leaves were 3.2 and 7.3, respectively. (e) The photosynthetic carbon metabolism of the chlorophyll mutant was through the reductive pentose phosphate cycle. (f) The CO(2) compensation points for the virescent and wild-type plants were similar. (g) The mutant and wild-type leaves have the same quantum yield in the red part of the visible spectrum, but the virescent leaves have a lower quantum yield in the blue part of the spectrum. (h) Virescent and wild-type leaves contain similar levels on a protein basis of several reductive pentose phosphate cycle enzymes.

Journal Article↗