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PubMed1978

Spectral properties of chlorophyll a monolayers in the presence of an exogenous electron donor and acceptor.

Chlorophyll a monolayers are studied at a nitrogen-water interface in the presence of a reducing or oxidizing agent: sodium ascorbate and benzyl viologen, respectively. Absorption spectra of the films are measured directly on the aqueous surface. With the aid of a computer, fourth derivative and difference spectra are determined. In the presence of ascorbate, a bathochromic shift of the absorption maximum to 693 nm can be induced as compared to 683 nm for a chlorophyll monolayer without any additives. In the presence of ascorbate, chlorophyll species at 676, 712 and 750 nm (present in a pure chlorophyll monolayer) are decreased or diminished. Illumination causes no change in the position of these absorption maxima; however, there is an increase of the absorbance of the main red absorption band. In the presence of benzyl viologen there is a hypsochromic shift of the red absorption maximum to 679 nm. Chlorophyll species at 670, 694, 712 and 740 nm (present in pure chlorophyll monolayers) are decreased or diminished upon addition of benzyl viologen. Upon illumination, there is a decrease in absorbance at 686 nm. It appears that the redox reagents induce the formation of specific chlorophyll aggregates, in the interfacial system, which might be analogous to the various chlorophyll species observed in green plant photosynthesis.

Ascorbic Acid↗
PubMed2001

Chlorophyll derived from Chlorella inhibits dioxin absorption from the gastrointestinal tract and accelerates dioxin excretion in rats.

We investigated the effects of chlorophyll derived from Chlorella on gastrointestinal absorption of seven types of polychlorinated dibenzo-p-dioxin (PCDD) and 10 types of polychlorinated dibenzofuran (PCDF) in Wistar rats. Twenty-eight rats were randomly distributed into seven groups (n = 4). After overnight food deprivation, rats were given 4 g of the basal diet or 4 g of the chlorophyll diet containing 0.01-0.5% chlorophyll one time on day 1; each diet also contained 0.2 mL PCDD and PCDF standard solutions. The amounts of fecal excretion of PCDD and PCDF congeners from days 1 to 5 in the group fed 0.01% chlorophyll were 64.8% for 1,2,3,7,8-pentaCDD, 78.6% for 1,2,3,4,7,8-hexaCDD, 73.5% for 1,2,3,6,7,8-hexaCDD, 58.5% for 1,2,3,7,8,9-hexaCDD, 33.3% for 1,2,3,4,6,7,8-heptaCDD, 85.7% for 1,2,3,7,8-pentaCDF, 77.3% for 2,3,4,7,8-pentaCDF, 88.6% for 1,2,3,4,7,8-hexaCDF, 78.0% for 1,2,3,6,7,8-hexaCDF, 62.5% for 1,2,3,7,8,9-hexaCDF, 84.1% for 2,3,4,6,7,8-hexaCDF, 41.7% for 1,2,3,4,6,7,8-heptaCDF, and 40.0% for 1,2,3,4,6,7,8-heptaCDF greater (p < 0.01) than those of the control group, respectively. The fecal excretion of PCDD and PCDF congeners was remarkably increased along with the increasing dietary chlorophyll. The amounts of PCDD and PCDF congeners in rats on day 5 administered dioxin mixtures were lower in the 0.01% chlorophyll group than in the control group, ranging from 3.5 to 50.0% for PCDD congeners and from 3.7 to 41.7% lower for PCDF congeners, except for 2,3,7,8-tetrachlorodibenzofuran. The amount of PCDD and PCDF congeners in rats was remarkably decreased along with the increasing dietary chlorophyll. These findings suggest that chlorophyll is effective for preventing dioxin absorption via foods.

Animals↗
PubMedDate not supplied

[Excitation energy transfer between chlorophyll a molecules in detergent solutions].

Chlorophyll-a absorption and luminescence as well as the transfer of electronic excitation energy between chlorophyll-a molecules were studied in micellar solutions of triton X-100 as a function of both chlorophyll-a and detergent concentrations. It is shown that the spectral properties of chlorophyll-a are closely related to the ratio between the concentrations of X-100 and chlorophyll-a. Concurrent evaluation of the curves for depolarization and relative quantum yield of fluorescence show that two different mechanisms of energy transfer are involved: energy transfer between monomers of chlorophyll-a, and energy transfer from excited monomers to aggregates of chlorophyll-a. Using the theoretical value for the critical distance of energy transfer (Ro=56-58 A) as well as experimental data from depolarization and fluorescence curves for solutions containing 3-10-3 M triton X-100 we determined the local concentration of chlorophyll-a in the detergent micelles.

Acetone↗
PubMed1988

[Control of chlorophyll a synthesis by phytochrome and cryptochrome in the red alga Corallina elongata Ellis et Soland].

Chlorophyll a synthesis in the red alga Corallina elongata is controlled by phytochrome and by a specific blue light photoreceptor. Although the estimated photoequilibrium of phytochrome is similar in blue and red light, the amount of chlorophyll accumulated is greater in blue light, which implies the action of cryptochrome, according to the criteria for the specific blue light photoreceptor involvement. The amount of chlorophyll synthesized is greater when the level of photoequilibrium approaches 65% (in blue and red light) than with higher levels (72.7% in white light and 70.8% in green light). The action of phytochrome is demonstrated by the induction of chlorophyll synthesis after red pulses and the reversion after far red pulses. The reversion is not complete but the percentage of reversibility is high (85-90%). The amount of chlorophyll accumulated is greater in darkness after the application of red light pulses than in white light after the same light pulses. The induction of chlorophyll synthesis is greater after red pulses than after continuous red light. The existence of a fast destruction of chlorophyll in continuous light is observed. This destruction is greater in the high photoequilibrium of phytochrome (70-72%). The turnover times and the induction mechanism of chlorophyll synthesis must be very fast. This indicates the existence of a possible rapid adaptation to the change in light quality and intensity in the marine system.

Chlorophyll↗
PubMed1998

Lepidimoide Promotes Light-Induced Chlorophyll Accumulation in Cotyledons of Sunflower Seedlings.

The effect of disaccharide lepidimoide on light-induced chlorophyll accumulation was studied in cotyledons of sunflower (Helianthus annuus L.) seedlings and detached cucumber (Cucumis sativus L.) cotyledons. From studies on the structure-activity relationships of lepidimoide, its analogs, and sucrose with respect to light-induced chlorophyll accumulation in the cotyledons of sunflower seedlings, both lepidimoide and the free carboxylic acid of lepidimoide (lepidimoic acid) showed the highest promoting activity, whereas the hydrogenated lepidimoide, which lacks a double bond in the C4, 5 position in uronic acid, showed lower activity than lepidimoide; however, sucrose exhibited very weak activity. These results suggest that lepidimoide acts as a new type of plant growth regulator, not simply as a carbon source providing energy. Lepidimoide promoted not only light-induced chlorophyll accumulation in sunflower cotyledons but also light-induced 5-aminolevulinic acid content, which is considered to be a rate-limiting step in chlorophyll biosynthesis. Lepidimoide with cytokinin stimulated the accumulation of chlorophyll and 5-aminolevulinic acid additively. In detached cucumber cotyledons, lepidimoide also promoted light-induced chlorophyll accumulation. These results indicate that lepidimoide, in cooperation with cytokinin, causes light-induced chlorophyll accumulation in the cotyledons of several dicot plant species by affecting the level of 5-aminolevulinic acid. Key Words. 5-Aminolevulinic acid accumulation-Chlorophyll accumulation-Cucumis sativus-Cytokinin-Helianthus annuus-Lepidimoic acid-Lepidimoide-Structure-activity relationship

Journal Article↗
PubMed1999

Chlorophyll b reduction during senescence of barley seedlings

During senescence of flowering plants, only breakdown products derived from chlorophyll a were detected although b disappears, too (Matile et al., 1996, Plant Physiol 112: 1403-1409). We investigated the possibility of chlorophyll b reduction during dark-induced senescence of barley (Hordeum vulgare L.) leaves. Plastids isolated from senescing leaves were lysed and incubated with NADPH. We found 7(1)-hydroxy-chlorophyll a, 7(1)-hydroxy-chlorophyllide a, and, after incubation with Zn-pheophorbide b, also Zn-7(1)-hydroxy-pheophorbide a, indicating activity of chlorophyll(ide) b reductase. The highest activity was found at day 2 of senescence when chlorophyll breakdown reached its highest rate. Chlorophyllase reached its highest activity under the same conditions only at days 4-6 of senescence. Based on the chlorophyll b reductase activity of plastids at day 2.5 of senescence (=100%), the bulk of activity (83%) was found in the thylakoids and only traces (5%) in the envelope fraction. Chlorophyll b reduction is considered to be an early and obligatory step of chlorophyll b breakdown.

Journal Article↗
PubMed2002

The chequered history of the development and use of simultaneous equations for the accurate determination of chlorophylls a and b.

Over the last half century, the most frequently used assay for chlorophylls in higher plants and green algae, the Arnon assay [Arnon DI (1949) Plant Physiol 24: 1-15], employed simultaneous equations for determining the concentrations of chlorophylls a and b in aqueous 80% acetone extracts of chlorophyllous plant and algal materials. These equations, however, were developed using extinction coefficients for chlorophylls a and b derived from early inaccurate spectrophotometric data. Thus, Arnon's equations give inaccurate chlorophyll a and b determinations and, therefore, inaccurate chlorophyll a/b ratios, which are always low. This paper describes how the ratios are increasingly and alarmingly low as the proportion of chlorophyll a increases. Accurate extinction coefficients for chlorophylls a and b, and the more reliable simultaneous equations derived from them, have been published subsequently by many research groups; these new post-Arnon equations, however, have been ignored by many researchers. This Minireview records the history of the development of accurate simultaneous equations and some difficulties and anomalies arising from the retention of Arnon's seriously flawed equations.

Journal Article↗
PubMed1978

Photosynthetic unit size, carotenoids, and chlorophyll-protein composition of Prochloron sp., a prokaryotic green alga.

Six samples of the prokaryotic, unicellular algae Prochloron sp., which occur in association with didemnid ascidians, were collected from various localities in the tropical Pacific Ocean, and their pigments and chlorophyll-protein complexes were identified and characterized. No phycobilin pigments were detected in any of the species. Chlorophylls a and b were present in ratios of a/b = 4.4-6.9. The major carotenoids were beta-carotene (70%) and zeaxanthin (20%). Minor carotenoids of one isolate were identified as echinenone, cryptoxanthin, isocryptoxanthin, mutachrome, and trihydroxy-beta-carotene; no epsilon-ring carotenoids were found in any sample. Except for the absence of glycosidic carotenoids, the overall pigment composition is typical of cyanobacteria. A chlorophyll a/b-protein complex was present in Prochloron; it was electrophoretically and spectrally indistinguishable from the light-harvesting chlorophyll a/b-protein of higher plants and green algae. It accounted for 26% (compared to approximately 50% in green plants) of the total chlorophyll; 17% was associated with a P700-chlorophyll a-protein. The photosynthetic unit size of 240 +/- 10 chlorophylls per P700 in Prochloron was about half that of eukaryotic green plants. A model is proposed for the in vivo organization of chlorophyll in Prochloron.

Journal Article↗
PubMed1990

Exploring the relationship between reflectance red edge and chlorophyll content in slash pine.

Chlorophyll is a key indicator of the physiological status of a forest canopy. However, its distribution may vary greatly in time and space, so that the estimation of chlorophyll content of canopies or branches by extrapolation from leaf values obtained by destructive sampling is labor intensive and potentially inaccurate. Chlorophyll content is related positively to the point of maximum slope in vegetation reflectance spectra which occurs at wavelengths between 690-740 nm and is known as the "red edge." The red edge of needles on individual slash pine (Pinus elliottii Engelm.) branches and in whole forest canopies was measured with a spectroradiometer. Branches were measured on the ground against a spectrally flat reflectance target and canopies were measured from observation towers against a spectrally variable understory and forest floor. There was a linear relationship between red edge and chlorophyll content of branches (R(2) = 0.91). Measurements of the red edge and this relationship were used to estimate the chlorophyll content of other branches with an error that was lower than that associated with the calorimetric (laboratory) method. There was no relationship between the red edge and the chlorophyll content of whole canopies. This can be explained by the overriding influence of the understory and forest floor, an influence that was illustrated by spectral mixture modeling. The results suggest that the red edge could be used to estimate the chlorophyll content in branches, but it is unlikely to be of value for the estimation of chlorophyll content in canopies unless the canopy cover is high.

Journal Article↗
PubMed1998

Chlorophyll synthesis in dark-grown pine primary needles

The pigment content of dark-grown primary needles of Pinus jeffreyi L. and Pinus sylvestris L. was determined by high-performance liquid chromatography. The state of protochlorophyllide a and of chlorophylls during dark growth were analyzed by in situ 77 K fluorescence spectroscopy. Both measurements unambiguously demonstrated that pine primary needles are able to synthesize chlorophyll in the dark. Norflurazon strongly inhibited both carotenoid and chlorophyll synthesis. Needles of plants treated with this inhibitor had low chlorophyll content, contained only traces of xanthophylls, and accumulated carotenoid precursors. The first form of chlorophyll detected in young pine needles grown in darkness had an emission maximum at 678 nm. Chlorophyll-protein complexes with in situ spectroscopic properties similar to those of fully green needles (685, 695, and 735 nm) later accumulated in untreated plants, whereas in norflurazon-treated plants the photosystem I emission at 735 nm was completely lacking. To better characterize the light-dependent chlorophyll biosynthetic pathway in pine needles, the 77 K fluorescence properties of in situ protochlorophyllide a spectral forms were studied. Photoactive and nonphotoactive protochlorophyllide a forms with emission properties similar to those reported for dark-grown angiosperms were found, but excitation spectra were substantially red shifted. Because of their lower chlorophyll content, norflurazon-treated plants were used to study the protochlorophyllide a photoreduction process triggered by one light flash. The first stable chlorophyllide photoproduct was a chlorophyllide a form emitting at 688 nm as in angiosperms. Further chlorophyllide a shifts usually observed in angiosperms were not detected. The rapid regeneration of photoactive protochlorophyllide a from nonphotoactive protochlorophyllide after one flash was demonstrated.

Journal Article↗
PubMed1976

Peridinin-Chlorophyll a Proteins of the Dinoflagellate Amphidinium carterae (Plymouth 450).

The marine dinoflagellate Amphidinium carterae (Plymouth 450) releases several water-soluble peridinin-chlorophyll a proteins after freezethawing. These chromoproteins have a molecular weight of 39.2 x 10(3) and are comprised of noncovalently bound peridinin and chlorophyll a and a nonoligomeric protein. They have distinct isoelectric points and may be resolved into six components by either isoelectric focusing on polyacrylamide gel or ion exchange chromatography. The predominant chromoprotein, which has a pI of 7.5, constitutes about 90% of the extractable peridinin-chlorophyll a protein. It consists of an alanine-rich apoprotein of molecular weight 31.8 x 10(3) stoichiometrically associated with 9 peridinin and 2 chlorophyll a molecules. Additionally, the peridinin-chlorophyll a proteins with pI values of 7.6 and 6.4 were purified and found to have amino acid and chromophore composition essentially identical with the pI 7.5 protein. Peridinin-chlorophyll a protein, pI 7.5, after treatment at alkaline pH was transformed into several more acid pI forms of the protein, strongly suggesting that the naturally occurring proteins are deamidation products of a single protein. Fluorescence excitation and emission spectra demonstrate that light energy absorbed by peridinin induces chlorophyll a fluorescence presumably by intramolecular energy transfer. The peridinin-chlorophyll a proteins presumably function in vivo as photosynthetic light-harvesting pigments.

Journal Article↗
PubMed1981

Euploidy in Ricinus: EUPLOIDY EFFECTS ON PHOTOSYNTHETIC ACTIVITY AND CONTENT OF CHLOROPHYLL-PROTEINS.

The effects of nuclear genome duplication on the chlorophyll-protein content and photochemical activity of chloroplasts, and photosynthetic rates in leaf tissue, have been evaluated in haploid, diploid, and tetraploid individuals of the castor bean, Ricinus communis L. Analysis of this euploid series revealed that both photosystem II (2,6-dichlorophenolindophenol reduction) and photosystem I oxygen uptake (N,N,N',N'-tetramethyl-p-phenylenediamine to methyl viologen) decrease in plastids isolated from cells with increasingly larger nuclear complement sizes. Photosynthetic O(2)-evolution and (14)CO(2)-fixation rates in leaf tissue from haploid, diploid, and tetraploid individuals were also found to decrease with the increase in size of the nuclear genome. Six chlorophyll-protein complexes, in addition to a zone of detergent complexed free pigment, were resolved from sodium dodecyl sulfate-solubilized thylakoid membranes from cells of all three ploidy levels. In addition to the P700-chlorophyll a-protein complex and the light-harvesting chlorophyll a/b-protein complex, four minor complexes were revealed, two containing only chlorophyll a and two containing both chlorophyll a and b. The relative distribution of chlorophyll among the resolved chlorophyll-protein complexes and free pigment was found to be similar for all three ploidy levels.

Journal Article↗
PubMed1983

Metabolism of Oat Leaves during Senescence : VII. The Interaction of Carbon Dioxide and Other Atmospheric Gases with Light in Controlling Chlorophyll Loss and Senescence.

In air largely freed from CO(2), senescence of isolated oat (Avena sativa cv Victory) seedling leaves is no longer prevented by white light; instead, the leaves lose both chlorophyll and protein as rapidly as in the dark. Senescence in light is also accelerated in pure O(2), but it is greatly delayed in N(2); 100% N(2) preserves both protein and chlorophyll in light and in darkness. In light in air, most of the compounds tested that had previously been found to delay or inhibit senescence in darkness actually promote the loss of chlorophyll, but they do not promote proteolysis. Under these conditions, proteolysis can therefore be separated from chlorophyll loss. But in light minus CO(2), where chlorophyll loss is rapid in controls, two of these same reagents prevent the chlorophyll loss. Unlike the many reagents whose action in light is thus the opposite of that in darkness, abscisic acid, which promotes chlorophyll loss in the dark, also promotes it in light with or without CO(2). Kinetin, which prevents chlorophyll loss in the dark, also prevents it in light minus CO(2). In general, therefore, the responses to light minus CO(2) are similar to the responses to darkness, and (with the exception of abscisic acid and kinetin) opposite to the response to light in air.

Journal Article↗
PubMed1983

Organization and Function of Chlorophyll in Membranes of Cyanobacteria during Iron Starvation.

Cells of Anacystis nidulans strain R2 and of Synechococcus cedrorum were grown in an iron-deficient medium. Iron starvation induced several pronounced effects without influencing the viability of these cells. The phycocyanin and chlorophyll contents of these cells were depressed, and the absorption maxima of membrane-bound chlorophyll was blue-shifted by 5 nanometers. Cells showed a dramatic increase in original and in maximal chlorophyll fluorescence when monitored at room temperature. Low temperature chlorophyll fluorescence revealed a loss in fluorescence at 696 and 716 nanometers; much of the remaining fluorescence emission was at 686 nanometers. These changes suggest an alteration of membrane composition and structure. This was documented by an electrophoretic analysis of iron-deficient membranes. The prominent findings were: (a) large chlorophyll-protein complexes were not observed in iron-deficient membranes, although the chlorophyll-binding proteins were present; (b) the staining of acrylamide gels with 3,3',5,5'-tetramethylbenzidine plus peroxide indicated that iron deficiency led to a decrease in the quantity of cytochromes. These results support a structural model of the relation between fluorescence and chlorophyll organization in Anacystis. In addition, they suggest a method for studying cytochrome and chlorophyll protein assembly in these membranes.

Journal Article↗
PubMed1985

Chlorophyll-Proteins and Electron Transport during Iron Nutrition-Mediated Chloroplast Development.

Chlorophyll-protein complexes and electron transport activities were measured during iron nutrition-mediated chloroplast development in sugar beet (Beta vulgaris L. cv F58-554H1). Results showed that the chlorophyll-protein complexes associated with the reaction centers of photosystem I (CP1) and photosystem II (CPa) and the electron transport activities of these two photosystems per leaf area increased rapidly during the first 24 to 48 hours of iron resupply to iron-deficient sugar beet plants. Bulk chlorophyll and the amounts of light-harvesting chlorophyll-proteins increased after a lag period of 24 hours. The changes in chlorophyll-proteins with time were apparently the cause of an initial increase, then decrease, in the chlorophyll a/b ratio during iron resupply. There was evidence that iron deficiency diminished photosystem I more than photosystem II. We propose that there are two distinct phases in iron nutrition-mediated chloroplast development: (a) the commencement of the synthesis of the lipid matrix of the thylakoid membrane, including a fully functioning electron transport (and photosynthetic) system, during the first 24 hours of iron resupply; and (b) after 24 to 48 hours, the formation of the bulk of the thylakoid proteins, including the light-harvesting chlorophyll-proteins with which the large increase in total chlorophyll is associated.

Journal Article↗
PubMed1986

A Temperature-Sensitive Chlorophyll b-Deficient Mutant of Sweetclover (Melilotus alba).

The ch4 mutant of sweetclover (Melilotus alba) has previously been demonstrated to be partially deficient in chlorophyll and to have a higher ratio of chlorophyll a to b than normal plants. We were able to substantiate these findings when plants were grown at 23 degrees C and lower (permissive temperatures). However, when grown at 26 degrees C (nonpermissive temperature) the plants produced small yellow leaves which exhibited one-twentieth the chlorophyll content of normal plants. Affected leaves did not increase their chlorophyll content when plants were incubated at permissive temperatures, but leaves which developed at the lower temperature contained increased amounts of chlorophyll. Similarly, only new leaves, not previously grown leaves, exhibited the yellow phenotype when the mutant plant was shifted from the permissive temperature to the nonpermissive temperature. Ribulose 1,5-bisphosphate carboxylase activity was decreased by half, relative to normal plants, in the mutant plants grown at the nonpermissive temperature, indicating that general protein synthesis was not greatly impaired and that the effect of the mutation was perhaps specific for chlorophyll content. HPLC analysis indicated that carotenoid content was not diminished to the same extent as chlorophyll and we have determined that the thylakoid protein kinase is not altered, as is the case for other chlorophyll b-deficient mutants. Experiments suggest that changes in photoperiod may be able to modulate the effect of temperature.

Journal Article↗
PubMed1995

Interactions between chlorophyll a and beta-carotene in nematic liquid crystals.

Fluorescence lifetime in the ps range, polarized absorption, polarized fluorescence spectra and delayed luminescence time resolved spectra were measured for chlorophyll a solutions with and without beta-carotene addition in nematic liquid crystal. Photoacoustic spectra of the same samples at various frequencies of light modulation were also taken. The frequency dependence of the photoacoustic spectra suggests that part of the excitation is converted into heat in a slow process (with a decay time of the order of ms). The lifetime results suggest that at used concentration some aggregation of the chlorophyll a occurs. The chlorophyll a molecules interact strongly with the beta-carotene forming some nonfluorescent or weakly fluorescent aggregates characterized by having various thermal deactivation yields and orientations in anisotropic matrix when compared to those of separated pigments. It seems that the aggregated forms of the chlorophylls are partially disrupted as a result of the their interaction with the beta-carotene. Singlet excitation of beta-carotene is not transferred to the fluorescent form of chlorophyll a. Delayed (in microsecond time range) luminescence of chlorophyll a is quenched by beta-carotene. This luminescence is located in the same spectral region as prompt fluorescence. Interactions between chlorophyll a and beta-carotene depend on the degree of pigment orientation and their aggregation.

Carotenoids↗
PubMed2002

The calculated in vitro and in vivo chlorophyll a absorption bandshape.

The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck-Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191-200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620-1627) at low temperatures. The calculated bandshapes are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll-protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540-850 cm(-1) occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode (nu < 200 cm(-1)) must be added or else the 262-cm(-1) mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape.

Chlorophyll↗