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[Transient states in the photoreactions of chlorophyll-protein complexes].

Transient short-lived species arising in chlorophyll-protein complexes of PS I on flash excitation were studied by means of flash-photolysis and luminescence methods. Complexes were isolated from chloroplasts by the solubilisation in SDS and subsequent electrophoresis. Three different types of reactions associated with: a) the triplet state of monomeric chlorophyll; b) redox reactions in reaction centres; c) photochemical reactions of monomeric chlorophyll were established on excitation. The arrangement of different forms of chlorophyll connected with the protein globule is discussed.

Chlorophyll↗

[Regularities of formation of chlorophyll-human serum albumin functionally active complexes in the aqueous medium].

In the system with constant content of the chlorophyll a and increasing amounts of human serum albumin, dependence of pigment incorporation into the complex upon interaction of its aqueous associates with protein solutions was studied by applying the gel filtration on Sephadex G-75 and by measuring light scattering and rate of sensitized photoreduction of the methyl red by ascorbic-acid. The curves were obtained after extraction of the chlorophyll by acetone from dry pigment-protein films formed after desiccation of the aqueous systems. Sigmoid character of the above dependences, their linearization in Hill's coordinates and the value of cooperativity coefficient close to 2 testifies in favour of the cooperative character of the complex formation, two pigment molecules reacting with a single protein molecule. Measurement of adsorption isotherms and their treatment with use of the Brunauer-Emmett-Teller theory of polymolecular adsorption make it possible to evaluate the maximum molar ratio of the pigment to the protein in the complex (close to 2). The pigment-pigment interaction suggests that the chlorophyll molecules adsorbed on the protein are in the state of loosely packed dimers. Deaggregation of aqueus pigment associates by the protein in the course of complex formation results in a considerable increase of the protosensitizing chlorophyll activity.

Binding Sites↗

[Chlorophyll a and b biosynthesis in the dark in etiolated leaves infiltrated by exogenous chlorophyllide a].

Exogenous chlorophyllide a was introduced into etiolated rye leaves by the vacuum-infiltration technique. Appearance and accumulation of chlorophylls a and b within the leaves are observed during continued darkening, protochlorophyllide photoreduction being avoided. The pigments are identified by the solubility in petroleum ether, paper chromatograms, the fluorescence maxima, the peculiarities of exciting light 430 and 460 nm effects on fluorescence intensity, the specific interaction with hydrochloric hydroxylamine. The conclusion is made that before illumination etioplasts already contain enzyme systems and substrates which provide esterification of chlorophyllide a to chlorophyll a and conversion of chlorophyll a into chlorophyll b.

Chlorophyll↗

Inhibition of chlorophyll biosynthesis by mercury in excised etiolated maize leaf segments during greening: effect of 2-oxoglutarate.

Mercury (0.01-1.0 mM) inhibited chlorophyll formation in greening maize leaf segments. However, supplementing incubation medium with 2-oxoglutarate, maintained substantially higher level of chlorophyll in absence of metal after an initial period of 8 hr. On preincubation of leaf segments with HgCl2, per cent inhibition of chlorophyll synthesis by metal was same in the presence and absence of 2-oxoglutarate. Supply of 2-oxoglutarate (0.1-10.0 mM) exerted concentration dependent effect on chlorophyll formation in absence or presence of metal. Increase in delta-amino levulinic acid dehydratase as well as NADH-glutamate synthase activity and decrease in NADH-glutamate dehydrogenase activity by 2-oxoglutarate in the presence of Hg suggested that glutamate for delta-amino levulinic acid synthesis could be made available from NH4+ assimilation via., glutamine synthetase/glutamate synthase pathway during mercury toxicity.

Aminolevulinic Acid↗

Measuring in-stream productivity: the potential of continuous chlorophyll and dissolved oxygen monitoring for assessing the ecological status of surface waters.

Continuous (hourly) measurements of dissolved oxygen and chlorophyll (determined by fluorimetry) were made for an inter-linked lowland river and canal system. The dissolved oxygen data were used to estimate daily rates of re-aeration, photosynthesis and respiration, using a process-based analytical technique (the Delta method). In-situ fluorimeter measurements of chlorophyll were ground-truthed on a fortnightly basis using laboratory methanol extraction of chlorophyll and spectrophotometric analysis. Water samples were also analysed for algal species on a fortnightly basis. The river and canal exhibited very similar rates of photosynthesis and respiration during the summer of 2001, despite much higher chlorophyll concentrations and total algal counts, indicating that benthic algae and/or aquatic macrophytes may be making an important contribution to photosynthesis rates in the river. Suspended algal populations in the canal are dominated by planktonic species, whereas the river has a higher proportion of species which are predominantly benthic in habitat. The river exhibited higher rates of respiration, reflecting a higher organic loading from external (e.g. sewage effluent) sources.

Chlorophyll↗

[Effect of phosphorus stress on chlorophyll biosynthesis, photosynthesis and biomass partitioning pattern of Fraxinus mandchurica seedlings].

Phosphorus is essential to forest trees for their growth and development, because of its important role in many metabolic processes of trees. But, most part of phosphorus in soils of Northeastern China is immobile and unavailable, and thus, many forest trees often suffer from phosphorus stress which affects the biomass accumulation of forest trees. The aim of this study is to understand how the chlorophyll biosynthesis, photosynthesis and biomass partitioning of Fraxinus mandchurica seedlings response to phosphorus stress. Sand culture experiment showed that when the seedlings were under phosphorus stress, their 5-aminolevulinic acid (ALA) biosynthesis rate and porphobilinogen (PBG) synthase activity were reduced, but no significant changes in chlorophyll a and b, total chlorophyll and carotenoid contents were found. The nitrogen content in leaves and roots and the phosphorus content in all parts of seedlings were reduced under phosphorus stress, and the reduction of N content in leaves induced the decrease of maximum quantum efficiency of PS II (Fv/Fm) efficiency of PS II photochemistry (phi(PS II)), electron transport rate (E(TR)), and maximum photosynthesis rate (Amax). The effect of phosphorus stress on chlorophyll biosynthesis didn't affect photosynthesis. Under phosphorus stress, the total biomass decreased, but more biomass was partitioned into roots.

Biomass↗

Impact of anaerobically treated and untreated (raw) distillery effluent irrigation on soil microflora, growth, total chlorophyll and protein contents of Phaseolus aureus L.

Impact of distillery effluent (untreated and treated) irrigation on soil microflora of the pots used for growing Phaseolus aureus L. was investigated. The growth of the P. aureus plants as affected by distillery effluent irrigation was also evaluated. The irrigation of the pots by 1-10% distillery effluent (anaerobically treated) stimulated the growth of the soil microflora (increased number of bacteria, fungi and actinomycetes) and P. aureus plants (increased shoot and root lengths, biomass, chlorophyll and protein contents). Further, 15-20% distillery effluent (anaerobically treated) had toxic effect on soil micro flora as indicated by reduced number of bacteria, fungi and actinomycetes. Reduction in shoot, root, lengths, biomass, chlorophyll, protein contents of P. aureus was also observed when irrigated by 15-20% treated distillery effluent. All the concentrations of raw distillery effluent reduced the bacterial population. However, the treated distillery effluent concentrations <10% had stimulatory effect on fungal and actinomycetes population. However, raw effluent concentrations >5% reduced the same. Raw distillery effluent was more toxic to P. aureus than treated distillery effluent as concentrations >5%, had reduced the growth (shoot, root length and biomass) of the test plant. Raw distillery effluent had adverse effect to total chlorophyll contents and all the test concentrations reduced the total chlorophyll level. However, untreated (raw) distillery effluent stimulated the protein content initially. It has been concluded from-present study that lower concentrations of the raw distillery effluent (1-5%) and treated distillery effluent (1-10%) had stimulated the growth of P. aureus and soil microflora except soil bacteria (inhibited by all the concentration of the raw effluent). However, higher concentrations (raw effluent: 10-20%; treated effluent 15-20%) had toxicity to test parameters.

Alcoholic Beverages↗

[Examination of chlorophyll fluorescence in sulfur-deprived cells of Chlamydomonas reinhardtii].

Modulated fluorometry (PAM) was applied for probing the photosynthesis in cells of C. reinhardtii during sulfur deprivation. A significant (up to a fourfold) increase in chlorophyll fluorescence yield (parameters F(o) and F(m)) normalized to chlorophyll concentration was shown for deprived cells. An analysis of nonphotochemical quenching of chlorophyll fluorescence indicated a considerable modification of the energy deactivation pathways in PS II of sulfur-deprived cells. Thus, starved cells exhibited a lower deltapH-dependent quenching of excited states and a higher thermal dissipation of excess light energy in reaction centers of PS II, as well as the transition of the photosynthetic apparatus primarily to state 2. However, these changes cannot cause the elevation of chlorophyll fluorescence in the cells under sulfur limitation. The phenomenon observed may be due to a partial dissociation of light-harvesting complexes from reaction centers of PS II and/or dysfunction of the dissipative cycle in PS II with cytochrome b559 as an intermediate.

Animals↗

[Spectral characteristics and the structure of chloroplasts upon blocking the early stages of chlorophyll biosynthesis].

The cotton mutant xantha (Gossypium hirsutum L.) with the blocked synthesis of 5-aminolevulinic acid in the light has been shown to accumulate chlorophyll 30 times less than the parent type. In chloroplasts of the mutant xantha, the formation of the membrane system is blocked at the earliest stages, mainly at the stage of bubbles and single short thylakoids. Only light-harvesting chlorophyll-a/b-protein complexes I and II with chlorophyll fluorescence maxima at 728 and 681 nm, respectively, are formed in plastid membranes of the mutant. It has been concluded that the genetic block of chlorophyll biosynthesis in the mutant xantha disturbs the formation and functioning of the complexes in reaction centers of PS-I and PS-II, inhibiting the development of the whole membrane system of chloroplasts at the stage of bubbles and single thylakoids.

Chlorophyll↗

Chlorophyll-proteins of the photosystem II antenna system.

The chlorophyll-protein complexes of purified maize photosystem II membranes were separated by a new mild gel electrophoresis system under conditions which maintained all of the major chlorophyll a/b-protein complex (LHCII) in the oligomeric form. This enabled the resolution of three chlorophyll a/b-proteins in the 26-31-kDa region which are normally obscured by monomeric LHCII. All chlorophyll a/b-proteins had unique polypeptide compositions and characteristic spectral properties. One of them (CP26) has not previously been described, and another (CP24) appeared to be identical to the connecting antenna of photosystem I (LHCI-680). Both CP24 and CP29 from maize had at least one epitope in common with the light-harvesting antennae of photosystem I, as shown by cross-reactivity with a monoclonal antibody raised against LHCI from barley thylakoids. A complex designated Chla.P2, which was capable of electron transport from diphenylcarbazide to 2,6-dichlorophenolindophenol, was isolated by nondenaturing gel electrophoresis. It lacked CP43, which therefore can be excluded as an essential component of the photosystem II reaction center core. Fractionation of octyl glucoside-solubilized photosystem II membranes in the presence and absence of Mg2+ enabled the isolation of the Chla . P2 complex and revealed the existence of a light-harvesting complex consisting of CP29, CP26, and CP24. This complex and the major light-harvesting system (LHCII) are postulated to transfer excitation energy independently to the photosystem II reaction center via CP43.

Chlorophyll↗

[Interaction of the photosystem 1 reaction center with antenna chlorophyll in a pigment-protein complex isolated from pea chloroplasts].

Using a specially developed phosporoscopic attachment to spectropolarimeter, light induced spectra of circular dichroism (CD) in region 600-750 nm were measured for a pigment protein complex of photosystem 1 (PC-1) isolated from pea chloroplast (chlorophyll : P700 = 40). Minor components at 672 and 678 nm are observed in light induced spectra besides the components of dimer splitting of P700 Qy transition at 691 and 698 nm. Haussian deconvolution of light induced CD spectra of P700 and low temperature CD spectrum of PC-1 indicates that minor components are due to forms of antenna chlorophylls Chl672 and Chl678, rotational strength of that is changed by 2-4% as a result of P700 oxidation. Long term incubation of PC-1 with Triton X-100 inhibits P700 and destroys longwave optically active chlorophyll forms. A strong relation between dichroic density of 693 nm band in CD spectrum of PC-1 and the value of light induced absorption change at 698 nm could be used to determine P700 concentration on the basis of CD spectrum of PC-1. Such a relation shows that Chl693 is an important component of photo-system 1 reaction center. It is suggested that P700 is not an isolated dimer but it is included in the local complex from 8-10 chlorophyll molecules (Chl672, Chl678, Chl686, Chl693).

Chlorophyll↗

[Spectral forms of chlorophyll and chloroplast structure of Chlamydomonas mutants with disortions in their light-gathering pigments].

A 2-3-fold reduction of chlorophyll content in pigment mutants of Chlamydomonas reinhardii is conditioned by the disturbances in light-harvesting pigments. When the activity of both photosystems is preserved, the reduction of short-wave forms of chlorophyll a (667, 678 nm) is accompanied by a fall of the fluorescence maximum at 685-690 nm; the disturbance of the long-wave forms with the adsorption maxima at 689, 698 an 703 nm results in a decrease of the chlorophyll fluorescence band at 707-718 nm. The long-wave forms of chlorophyll appertain to the pigment-protein complex of PS-1 which is not involved in the formation of contacts between the grand thylacoids.

Chlamydomonas↗

Absorption of phytol from dietary chlorophyll in the rat.

The fate of ingested chlorophyll-particularly of the phytol portion of the molecule-was studied. Uniformly (14)C-labeled pheophytin a (the Mg-free derivative of chlorophyll a) was prepared from an extract of tobacco leaves grown in (14)CO(2), and was administered by stomach tube to rats in which the thoracic duct had been cannulated. Only about 2% of the administered radioactivity was absorbed in 24 hr, largely into the thoracic duct lymph. Moreover, only a fraction of this lymph radioactivity was derived from phytol (i.e., was found in phytol, phytenic acid, or phytanic acid). The results indicated that not more than 1-2% of chlorophyll phytol is available for absorption by the rat. Similarly, after the administration of whole spinach or spinach extract (not labeled) to rats, only about 1% of the total phytol content was absorbed into the intestinal lymph. Nearly all of the administered phytol was found in the feces and the contents of the colon, and was still largely in the form of pheophytin. The study also indicated that little of the nonphytol portion of the chlorophyll molecule is absorbed.

Animal Nutritional Physiological Phenomena↗

[Chlorophyll-protein complexes from green algae and higher plants. Heterogeneity of chloroplast complexes from dimorphous tissue of C4 plant leaves].

It was demonstrated that the decrease of the activity of photosystem II in agranal chloroplasts of bundle sheath cells of malate C4 plants is due to a loss of the chlorophyll-protein complex of this photosystem. This is paralleled with an increase in the relative amount of the chlorophyll--protein complex of photosystem I and a partial loss of the light-harvesting pigmentprotein complex. These two events may account for the high activity of photosystem I and for the low content of chlorophyll b in the plastids. The cumulative data are indicative of a close interrelationship between the granal state of the chloroplast membranes and the presence of the chlorophyll--protein complex of photosystem II.

Chlorophyll↗

[Chlorophyll phosphorescence in leaves and cells of algae].

Phosphorescence and delayed fluorescence of chlorophyll have been observed in frozen suspensions of green, blue-green and red alga, normal and mutant leaves of pea, kidney bean and maize at the temperature range from --196 to --70 degrees C. The phosphorescence maximum lies at 960--980 nm, excitation maximum--at 674+/-2 nm, lifetime is 1.5--2.5 msec, quantum yield vaires in the range of 0.03--3 x 10(-6), being much lower than that of chlorophyll phosphorescence in solutions. The weakest phosphorescence was found in normal leaves, the strongest one--in cells of Scendesmus and leaves of xi-carotene mutants of maize. The data suggest that phosphorescence belongs to antenna chlorophyll and phosphorescence quenching is due to energy migration from singlet and triplet states of antenna to non-phosphorescent forms of chlorophyll and carotenoids.

Chlorophyll↗

[Antenna form of chlorophyll of photosystem II in chloroplasts].

Low temperature fluorescence spectra and second derivatives of chlorophyll absorption spectra in leaves, chloroplasts of mesophyll and parenchyme bundle sheath cells (BSC) were studied. It has been shown that in ontogenesis of BSC chloroplasts of Zea mays leaves along with a decrease of the activity of the PS-2 and a reduction of granal regions the fluorescence maximum of chlorophyll decreases at 695 nm. The change of this fluorescence band is concerned with the disturbance of the form of chlorophyll "a" absorbing at 684 nm and performing the function of an antenna of the pigment-protein complex of PS-2. Similarities in the distribution of chlorophyll forms between three pigment-protein complexes of chloroplast membranes in green algae and higher plants are discussed.

Chlorophyll↗

[Electron transport in the chlorophyll aggregate oxidation reaction].

Flash photolysis study was carried out of electron transfer during rho-benzoquinone-photooxidation of monomeric and aggregated molecules of chlorophyll "a" in aqueous solutions of serum albumin and triton X-100. It has been found that in the presence of rho-benzoquinone oxidation of monomeres and aggregates of chlorophyll takes place; it results in the formation of the pigment cation-radicals. The kinetic analysis of the pattern of electron transfer during aggregates photooxidation enables a conclusion that oxidation proceeds only via the triplet state of the pigment molecules. Study of the transformation of cation-radicals of monomeres and aggregates showed a difference in the death of radicals. For chlorophyll monomeres the death of cation-radicals is described by the 2nd order equation and is conditioned by the recombination of ion-radicals of the pigment and acceptor. The death of aggregate cation-radicals proceeds according to the 1st order reaction. The results obtained point to possible participation of chlorophyll triplet state in primary photochemical reactions of photosynthesis.

Benzoquinones↗

[Variability in chlorophyll accumulation and the structure of the chloroplasts in the daughter strains of the phenotypically yellow mutant Y-4 of Chlamydomonas reinhardi].

The analysis of a group of recombinant strains of phenotypically yellow mutant Y-4 Chlamydomonas reinhardii has shown a considerable variability in displaying the degree of pigmentation. Chlorophyll "a" is the first to accumulate in chloroplasts. Chlorophyll "b" was found in strains when the content of chlorophyll "a" reached 1% of its concentration in cells of the wild type, The occurrence of spectral forms of chlorophyll "a" at 661, 667, 678, 685, 698 and 703 does not correlate with its quantitative accumulation. Variability in pigment accumulation is accompanied by changes both in the structural organization of the membrane system of chloroplasts and in the functional activity of photosystems. The degree of development of chloroplast structure in the group of recombinant strains varies from the formation of vesicules to well developed tilakoids and their arrangement in grains.

Chlamydomonas↗