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Photocatalytic conversion of organic compounds has recently emerged as a cost‐effective, safe, and easy‐to‐operate procedure to synthesize value‐added materials. In this study, the magnetic titanium dioxide‐based (Fe3O4/SiO2/TiO2) photocatalyst was designed to synthesize conjugated derivatives of tetrahydroquinoline through a photoinduced electron transfer (PET) reaction. Chlorophyll b was immobilized on the surface of magnetic titanium dioxide, as a natural visible‐light‐sensitive compound using 3‐aminopropyltriethoxysilane (APTES) as a coupling agent containing terminal amine (Fe3O4/SiO2/TiO2‐NH2‐Chb) to improve light harvesting ability. Fourier transform infrared (FT‐IR), powder X‐ray diffraction (PXRD), thermogravimetric analysis (TGA), energy‐dispersive X‐ray spectrometer (EDS), and vibrating sample magnetometer (VSM) results confirmed the successful synthesis of Fe3O4/SiO2/TiO2‐NH2‐Chb. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images displayed the preserved spherical morphology of Fe3O4/SiO2/TiO2‐NH2‐Chb. Chlorophyll b‐modified magnetic titanium dioxide was highly active under visible‐light irradiation toward the cyclization of (E)‐3‐[4‐(dimethylamino)phenyl)]‐1‐arylprop‐2‐en‐1‐one with 1‐aryl‐1H‐pyrrole‐2,5‐dione to achieve new tetrahydroquinoline derivatives with conjugated structure in high yields at ambient temperature, in air. The incorporation of chlorophyll b in the photocatalyst plays an important role in the photocatalytic mechanism, facilitating photoinduced electron transfer to the conduction band of TiO2. Moreover, the magnetic property enabled easy recovery of the photocatalyst and improved its reusability up to three runs. The characteristics of tetrahydroquinoline derivatives were studied by FT‐IR, CHN, 1H NMR, and 13C NMR analyses. [ABSTRACT FROM AUTHOR]

Chlorophyll b was extracted from Heliotropium europaeum plant, then immobilized on magnetic nanoparticles (Fe3O4@SiO2@Chl‐Mg) and found as an efficient and green catalyst for the preparation of a variety of benzimidazoles and spirooxindoles in mild conditions. The catalyst was fully characterized by Fourier‐transform infrared (FTIR), ultraviolet–visible (UV–vis) spectroscopy, X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDX), thermogravimetric (TGA), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) analyses. To prove the catalytic influence of Mg over the reactions, the catalytic activity of the demetalated chlorophyll b as well as some other control experiments was investigated. High to excellent yields were achieved for all entries, whether benzimidazole or spirooxindole derivatives at short reaction times. The catalyst could be recovered and reused for several consecutive runs by a simple external magnetic field without any considerable reactivity loss. The properties of the recovered catalyst were investigated by various analyses. Finally, the reasonable mechanisms were proposed for the reactions based on the literature. [ABSTRACT FROM AUTHOR]

Abstract: Chlorophyll a and chlorophyll b have been isolated and purified by counter current chromatography. The 1H‐, 13C‐, and 15N‐NMR spectra were recorded and compared for the 2 molecules by using arguments based on classical structural properties. This interpretation is fully corroborated by high‐level ab initio quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Chlorophyll exists since ca. 3 billion years and is at begin of the evolution. This chiral, green Mg-porphyrin-complex absorbs as a photosensitizer in the antennas of the light-harvesting complexes of chloroplasts all parts of visible light except of green light. This energy is transferred to the reaction centres of oxygenic photosynthesis. By this redox reaction carbon dioxide and water are transformed into carbohydrates and oxygen. We describe how the structures of chlorophylls were elucidated, discuss structure-property relations, the relationship to heme of blood, everyday uses, and how Green has influenced our language. The isolation of pure chlorophyll a from spinach is an experimental challenge, which we report in detail. All analytical spectra were recorded and are reproduced and interpreted either in the main part or in the supporting information. [ABSTRACT FROM AUTHOR]

The article discusses the protocol for the simultaneous quantification of chlorophyll (Chl) a and b described by D. I. Arnon in 1949. Topics covered include the citations received by Arnon's study, the imprecision of Arnon's equations, and an unusual bimodal pattern revealed in a chronological analysis of the citations of Arnon's paper.

Chlorophyll a and chlorophyll b are interconverted in the chlorophyll cycle. The initial step in the conversion of chlorophyll b to chlorophyll a is catalyzed by the chlorophyll b reductases NON- YELLOW COLORING 1 ( NYC1) and NYC1-like ( NOL), which convert chlorophyll b to 7-hydroxymethyl chlorophyll a. This step is also the first stage in the degradation of the light-harvesting chlorophyll a/ b protein complex ( LHC). In this study, we examined the effect of chlorophyll b on the level of NYC1. NYC1 mRNA and NYC1 protein were in low abundance in green leaves, but their levels increased in response to dark-induced senescence. When the level of chlorophyll b was enhanced by the introduction of a truncated chlorophyllide a oxygenase gene and the leaves were incubated in the dark, the amount of NYC1 was greatly increased compared with that of the wild type; however, the amount of NYC1 mRNA was the same as in the wild type. In contrast, NYC1 did not accumulate in the mutant without chlorophyll b, even though the NYC1 mRNA level was high after incubation in the dark. Quantification of the LHC protein showed no strong correlation between the levels of NYC1 and LHC proteins. However, the level of chlorophyll fluorescence of the dark adapted plant ( Fo) was closely related to the accumulation of NYC1, suggesting that the NYC1 level is related to the energetically uncoupled LHC. These results and previous reports on the degradation of chlorophyllide a oxygenase suggest that the a feedforward and feedback network is included in chlorophyll cycle. [ABSTRACT FROM AUTHOR]

Chlorophyll is a deleterious molecule that generates reactive oxygen species and must be converted to non-toxic molecules during plant senescence. The degradation pathway of chlorophyll a has been determined; however, that of chlorophyll b is poorly understood, and multiple pathways of chlorophyll b degradation have been proposed. In this study, we found that chlorophyll b is degraded by a single pathway, and elucidated the importance of this pathway in avoiding cell death. In order to determine the chlorophyll degradation pathway, we first examined the substrate specificity of 7-hydroxymethyl chlorophyll a reductase. 7-hydroxymethyl chlorophyll a reductase reduces 7-hydroxymethyl chlorophyll a but not 7-hydroxymethyl pheophytin a or 7-hydroxymethyl pheophorbide a. These results indicate that the first step of chlorophyll b degradation is its conversion to 7-hydroxymethyl chlorophyll a by chlorophyll b reductase, although chlorophyll b reductase has broad substrate specificity. In vitro experiments showed that chlorophyll b reductase converted all of the chlorophyll b in the light-harvesting chlorophyll a/ b protein complex to 7-hydroxymethyl chlorophyll a, but did not completely convert chlorophyll b in the core antenna complexes. When plants whose core antennae contained chlorophyll b were incubated in the dark, chlorophyll b was not properly degraded, and the accumulation of 7-hydroxymethyl pheophorbide a and pheophorbide b resulted in cell death. This result indicates that chlorophyll b is not properly degraded when it exists in core antenna complexes. Based on these results, we discuss the importance of the proper degradation of chlorophyll b. [ABSTRACT FROM AUTHOR]

Effects of chlorophyll b, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) on the oxidation of canola oil under 1700 lux light at 10 °C were studied by determining the headspace oxygen depletion and peroxide value. Chlorophyll b increased the oil oxidation under light via production of singlet oxygen. PC and PE did not affect the headspace oxygen depletion and peroxide formation in the oil in the absence of chlorophyll b at 10 °C; however, they increased in the presence of chlorophyll, with higher effect of PC than PE. Chlorophyll was degraded during the oil photooxidation and PC and PE decreased its photodecomposition with higher protection by PC than PE. There was no effect of light or singlet oxygen on PC and PE during the oil photooxidation. The results clearly showed that PC and PE were prooxidants in the photooxidation of canola oil containing chlorophyll b by protecting it from photodecomposition, and thus PC and PE should be removed from the oil containing chlorophyll to improve the photooxidative stability. [ABSTRACT FROM AUTHOR]

Effects of photosensitizers including riboflavin, chlorophyll b, or methylene blue on the stability of daidzein and genistein were studied in model systems by high-performance liquid chromatography (HPLC). Concentration of daidzein and genistein in 80% methanol with riboflavin under light for 7 h was significantly decreased with the apparent 1st-order rate constants of 0.234 and 0.193/h, respectively, ( P < 0.05), while those without riboflavin under light did not change significantly ( P > 0.05). The stability of isoflavone aglycones in the dark did not change significantly irrespective of the presence of riboflavin ( P > 0.05). The concentrations of daidzein and genistein in chlorophyll b or methylene blue model systems under light were not significantly different from those in the dark for 7 h ( P > 0.05). Addition of sodium azide increased the stability of daidzein and genistein in riboflavin photosensitization with concentration dependent manner. However, the protective effects of β-carotene addition on the photodegradation of isoflavones were not high. The stability difference of daidzein and genistein in riboflavin photosensitization may be due to the high reactivity of riboflavin through type I pathway, although singlet oxygen may be involved in part. [ABSTRACT FROM AUTHOR]

We examined the functional relationship between chlorophyll concentrations and light spectral absorption in 16 species of woody, vine and herbaceous plants in northern Japan. Leaves of each species from under forest shade and in more open sites were measured for chlorophyll, specific leaf area (SLA) and spectral absorption. In all species, SLA increased and the Chl a:b ratio declined in shade- vs open-grown leaves indicating an adaptive adjustment to forest shade in these leaf characters. However, the expected increase in the ratio of 680 to 700 nm absorption in shade leaves did not occur in all species. Light absorption at 680 relative to 700 nm was lower in the shade leaves of Acer japonicum, Kalopanax pictus, Panax japonicus and Petasites japonicus even with a reduced Chl a:b, a commonly accepted indicator of shade adaptation. Therefore, spectral measurements in these species failed to support Chl concentrations that were expected to confer an improvement in the absorption of red light (<680nm) deficient relative to far-red light (>700 nm) in the forest shade. Compared with other species, the absorption pattern of these four ‘non-conforming’ species is associated with a higher ratio of shade:open leaves in reflectance spectra in the 600–750 nm range. This suggests an increased reflectance in shade leaves caused by changes in leaf surface properties which are not immediately apparent. We conclude that adaptive spectral absorption cannot always be inferred from changes in specific leaf area and chlorophyll a and b concentrations. [ABSTRACT FROM AUTHOR]

Seedlings of Phaseolus aureus ROXB were grown under 12/12 h light/dark cycles with the light period at 32.5°C and darkness at 10°C (normal conditions N) or with light at 10°C and darkness at 32.5°C (inverse conditions, i). I-conditions affected the level of chlorophyll aid carotenoids (very low), monogalactosyldiacylgycerol (low) and phosphatidylinositol (high) in the leaves. Leaves of I-seedlings showed a sharp and durable decline of relative water content during the low temperature phase. For the N-seedlings, loss of water was restricted to the end of this period. The loss of water was accompanied by visible symptoms of wilting at specific times of day. Although the pigment content remained nearly unchanged, ABA content of leaves of both N- and I-seedlings increased during water stress. Upon return to the warm period, ABA level continued to increase after the leaves had regained turgor, this 'after stress' increase being more pronounced in the leaves of I-seedlings. Exogenous application of ABA induced a slight increase in the content of phospholipids in N- and I-eaves and a decrease in free fatty acids, whereas monogalactosyldiacylglycerol content was significantly reduced in N-leaves after application of ABA. Upon transfer of 1-plants to 20°C for 12 h during the light period, pigment and chloroplastic lipid content increased rapidly whereas upon a further exposure to 1(FC in light, pigments and especially monogalactosyldiacylglycerol were lost. The control of pigment and lipid metabolism and the role of ABA during chilling stress are discussed. [ABSTRACT FROM AUTHOR]

It is demonstrated that chlorophyll b does not only derive from chlorophyll a, but is also formed separately from an in vivo-occurring chlorophyllide b. The branching point for the latter synthesis is at the level of chlorophylhde, since no protochlorophyllide b was detectable. We have indications that the enzyme oxidizing chlorophyll a to chlorophyll b accepts also non-phytylated 17,18 dihydroporphyrins and is not restricted to chlorophylls. Preparations of chiorophyllide a and chlorophyll a could both be transferred with the same enzyme fraction to chiorophyllide b and chlorophyll b, respectively. Preliminary experiments show this enzyme to be membrane bound and light independent. An updated scheme for chlorophyll b biosynthesis is presented. [ABSTRACT FROM AUTHOR]

Tabtoxin is the chlorosis-inducing dipeptide toxin produced by Pseudomonas syringae pv. tabaci, causal agent of the wildfire disease of Nicotiana tabacum L. cv. White Burley. In plant tissue it is hydrolysed to yield the amino acid tabtoxinine β-lactam, which inactivates glutamine synthetase (EC 6.3.1.2). This study sought to identify those physiological alterations caused by the inactivation of glutamine synthetase and which were involved in the development of the chlorotic symptom. In tobacco (Nicotiana tabacum L. cv. White Burley) leaves injected with concentrations of taboxin that caused the inactivation of glutamine synthetase, photosynthesis was rapidly inhibited when the tissue was illuminated. This was closely followed by losses in leaf pigments, particularly chlorophyll a, and the ratio of chlorophyll a/b declined, indicating photochemical destruction. The rapid inhibition of photosynthesis in green tissue was due to reduced quantum efficiency, indicating a lesion in the light reactions. In chlorotic tissue, photosynthesis was limited by the chlorophyll level. The results indicated that the inhibition of photosynthesis may he instrumental in development of the chlorotic symptoms. [ABSTRACT FROM AUTHOR]

Corn (Zea mays L. cv. OP Golden Bantum) was grown under low irradiance blue, red or blue plus red light. Red was more effective than blue light for synthesis of ChI a, b and light-harvesting proteins (LHC-2) associated with photosystem 2 (PS2). Blue light was slightly more effective for synthesis of light-harvesting proteins (LHC-1) associated with photosystem 1 (PS1), but below a fluence rate of 1 μmol m-2s-1 the response to blue vs that to red depended on irradiance level. Blue light containing a small amount of red light was as effective as red light for ChI a and b synthesis, but no more effective than blue light for LHC-2 synthesis. Adding small amounts of blue light to red repressed the effect of red light on LHC-2 synthesis and produced irradiance response curves similar to those produced by blue alone for LHC-2 synthesis. This repression by blue light depended on the ratio of red to blue and the level of the blue light. [ABSTRACT FROM AUTHOR]

When dark grown leaves of wheat (Triticum aestivum L.) were given a brief irradiation, there was an immediate onset of chlorophyll (Chl) b synthesis in the dark. This synthesis led to a rather slow accumulation of Chl b, which ceased when the Chl b/Chl a ratio had reached a value of about 0.1. The Chl b synthesis occurred also when the seedlings were treated with the herbicide SAN 9789. Leaves grown under different intensities of red light accumulated Chl b and Chl a, resulting in a ratio Chl b/Chl a which depended on the light intensity, little light intensity was low, Chl a accumulated to a level about ten times the level of PChlide of the dark grown leaves. This occurred without any increase in the Chl b/Chl a ratio. There was no difference between SAN 9789-treated seedlings and water controls in this respect. Above a certain threshold of irradiance, the Chl b/Chl b ratio in the control leaves increased rapidly with the irradiation intensity. The increase in Chl b/Chl a ratio coincided with formation of grana in the plastids. This increase was not found and grana formation was completely absent in the seedlings treated with SAN 9789. The possibility of two different stages in the Chl b synthesis is discussed. [ABSTRACT FROM AUTHOR]

Pigment compositions of 16 coccoid eukaryotic ultraplanktonic clones isolated from coastal and oceanic waters were investigated by high-performance liquid chromatography (HPLC). Four distinct pigment signatures were observed, and clones were classified into subgroups based on the presence or absence and relative abundances of selected chlorophylls and carotenoids. The first subgroup (5 clones) was pigmented like chlorophyll b-containing higher plants and resembled true chlorophycean algae. The second subgroup (3 clones) contained chlorophyll b and relatively high levels of prasinoxanthin, a carotenoid characteristic of certain members of the Prasinophyceae (sometimes grouped as the Micromonadophyceae). The third subgroup (5 clones) was pigmented in a similar fshion but had a twofold lower prasinoxanthin-to-chlorophyll a ratio and an unidentified carotenoid. The fourth subgroup (3 clones) lacked chlorophyll b and was pigmented like certain members of the Chrysophyceae (e.g. 19′-butanoyloxyfucoxan-thin-containing Pelagococcus subviridis Norris). On line diode array spectral analysis of selected clonal extracts revealed the presence of Mg 2,4-divinylphaeoporphyrin a, monomethyl ester-like and chlorophyll c-like pigments in representatives of the prasinophyte-like and chrysophyte-like clones, respectively. These findings plus the occurrence of chlorophyll b, prasinoxanthin and 19′-butanoyloxyfucoxanthin in the North Atlantic Ocean suggest that chrysophyte- and prasinophyte-like organisms can be important biomass components of marine phytoplankton. [ABSTRACT FROM AUTHOR]

A preparation of prolamellar bodies from wheat etioplasts was used as a source for NADPH-protochiorophyllide oxidoreductase (pchlide reductase). The enzyme was solubilized with Triton X-100 after reduction of the endogenous photoconvertilale protochlorophyllide a to chlorophyllide a by saturating illumination. Protochlorophylls a and b, protochlorophyllide a and zinc protopheophorbide b were added to the soluble enzyme preparation to determine if they were reduced in the dark or in the light. None of the compounds were reduced (with NADPH) in the dark; however, light-dependent reduction was demonstrated with protochlorophyllide a and zinc protopheophorbide b. The yield was approximately 50% for both substrates. Photoreduction did not occur with the esterified protochlorophylls a and b. Photoreduction of zinc protopheophorbide b, the zinc analogue of protochlorophyllide b, is the first demonstration of the reduction of a chlorophyll-b-related compound by pchlide reductase. [ABSTRACT FROM AUTHOR]