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1.
Int J Mol Sci ; 25(3)2024 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-38339109

RESUMO

The central ion Mg2+ is responsible for the differences between chlorophyll a and its free base in their reactivity toward metal ions and thus their resistance to oxidation. We present here the results of spectroscopic (electronic absorption and emission, circular dichroism, and electron paramagnetic resonance), spectroelectrochemical, and computational (based on density functional theory) investigations into the mechanism of pheophytin, a degradation that occurs in the presence of Cu ions and O2. The processes leading to the formation of the linear form of tetrapyrrole are very complex and involve the weakening of the methine bridge due to an electron withdrawal by Cu(II) and the activation of O2, which provides protection to the free ends of the opening macrocycle. These mechanistic insights are related to the naturally occurring damage to the photosynthetic apparatus of plants growing on metal-contaminated soils.


Assuntos
Cobre , Feofitinas , Espécies Reativas de Oxigênio/metabolismo , Cobre/química , Clorofila A , Oxirredução , Metais , Íons , Espectroscopia de Ressonância de Spin Eletrônica , Oxigênio/metabolismo
2.
J Sci Food Agric ; 104(15): 9410-9422, 2024 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-39101245

RESUMO

BACKGROUND: The color of green tea is an important quality indicator. In recent years, shading of tea (Camellia sinensis L.) plants has been widely adopted for green tea production to enhance its green color and umami taste. In this study, we identified factors that influence green tea color by (i) examining variation in the chlorophyll content of fresh new tea shoots among cultivars, cropping seasons, and the degree of shading, (ii) investigating the rate of conversion of chlorophyll to pheophytin during the tea manufacturing process, specifically with steaming duration, and (iii) analyzing the effects of the new tea shoot properties and the steaming process on colorimetric values of the steamed new tea shoots. RESULTS: Multiple regression analysis revealed that three factors contributed to the rate of conversion of each chlorophyll type to pheophytin in steamed new tea shoots (ranked by importance): steaming duration > each chlorophyll type (chlorophyll-a and chlorophyll-b) content of fresh new tea shoots > pH. The colorimetric hue angle (h) value of steamed new tea shoots was influenced by four factors (ranked by importance): steaming duration > total chlorophyll (chlorophyll-a + chlorophyll-b) content in fresh new tea shoots > pH > chlorophyll-a/chlorophyll-b ratio in fresh new tea shoots. CONCLUSION: Differences in the color of new tea shoots can be explained by the aforementioned four factors. The findings will be useful for cultivar selection, and determining the appropriate degree of shading and steaming duration, to produce high-quality green teas with a good appearance. © 2024 Society of Chemical Industry.


Assuntos
Camellia sinensis , Clorofila A , Clorofila , Cor , Clorofila/análise , Clorofila/química , Camellia sinensis/química , Camellia sinensis/crescimento & desenvolvimento , Camellia sinensis/metabolismo , Concentração de Íons de Hidrogênio , Clorofila A/análise , Clorofila A/química , Vapor/análise , Manipulação de Alimentos/métodos , Chá/química , Folhas de Planta/química , Folhas de Planta/metabolismo
3.
Molecules ; 28(10)2023 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-37241936

RESUMO

BACKGROUND: Cathepsin K, which is involved in bone resorption, is a good target for treating osteoporosis, but no clinically approved medicine has been developed. Recently, allosteric inhibitors with high specificity and few side effects have been attracting attention for use in new medicines. METHODS: Cathepsin K inhibitors were isolated from the methanol extract of Chamaecrista nomame (Leguminosae) using cathepsin K inhibition activity-assisted multi-step chromatography. Standard kinetic analysis was employed to examine the mechanism of cathepsin K inhibition when an isolated inhibitor and its derivative were used. The allosteric binding of these cathepsin K inhibitors was supported by a docking study using AutoDock vina. Combinations of allosteric cathepsin K inhibitors expected to bind to different allosteric sites were examined by means of cathepsin K inhibition assay. RESULTS: Two types of cathepsin K inhibitors were identified in the methanol extract of Chamaecrista nomame. One type consisted of cassiaoccidentalin B and torachrysone 8-ß-gentiobioside, and inhibited both cathepsin K and B with similar inhibitory potential, while the other type of inhibitor consisted of pheophytin a, and inhibited cathepsin K but not cathepsin B, suggesting that pheophytin a binds to an allosteric site of cathepsin K. Kinetic analysis of inhibitory activity suggested that pheophytin a and its derivative, pheophorbide b, bind allosterically to cathepsin K. This possibility was supported by a docking study on cathepsin K. The cathepsin K inhibitory activity of pheophytin a and pheophorbide b was enhanced by combining them with the allosteric inhibitors NSC 13345 and NSC94914, which bind to other allosteric sites on cathepsin K. CONCLUSIONS: Different allosteric inhibitors that bind to different sites in combination, as shown in this study, may be useful for designing new allosteric inhibitory drugs with high specificity and few side effects.


Assuntos
Reabsorção Óssea , Metanol , Humanos , Catepsina K/metabolismo , Sítio Alostérico , Cinética , Catepsinas/metabolismo
4.
Biochemistry (Mosc) ; 87(10): 1119-1129, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36273880

RESUMO

To elucidate the mechanism of site-selective chemical replacement of chromophores in the reaction centers (RCs) of photosynthetic bacteria by external pigments, we investigated how the efficiency of incorporation of plant pheophytin a (Pheo) into the binding sites for bacteriopheophytin a molecules (BPheo) in the isolated Rhodobacter sphaeroides R-26 RCs depended on the incubation medium temperature, Pheo aggregation state, and the presence of organic solvent (acetone). When Pheo was in a form of monomers in free detergent micelles in a water-detergent incubation medium, the degree of selective replacement of photochemically inactive BPheo HB molecules upon incubation of the RC/Pheo mixture at 5°C was ~15%. The exchange efficiency increased to 40% upon incubation at 25°C and reached 100% at the same temperature when 10% acetone was added to the incubation medium. At both 5 and 25°C, the degree of pigment exchange increased approximately twice, when a mixture of Pheo monomers and dimers in the presence of 10% acetone was used as the incubation medium. The removal of acetone from this medium with the preservation of pigment forms led to a significant decrease in the efficiency of Pheo incorporation. The effect of acetone on the pigment exchange was also observed at an elevated incubation temperature (43.5°C), when functionally active BPheo HA molecules were partially replaced. The results are discussed in terms of the mechanism according to which (i) the temperature-dependent internal movements of the RC protein facilitate the release of the BPheo molecule from the binding site with simultaneous insertion of the Pheo molecule into the same site in a coupled process, (ii) the role of temperature largely depends on the steric accessibility of binding pockets in the RC protein, (iii) the incorporation of Pheo occurs from a pool of monomeric molecules included in the RC-detergent micelles, and (iv) the presence of acetone in the incubation medium facilitates the exchange of Pheo monomers between micelles in the solution and the detergent belt of the RC complex.


Assuntos
Complexo de Proteínas do Centro de Reação Fotossintética , Rhodobacter sphaeroides , Rhodobacter sphaeroides/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Detergentes , Micelas , Acetona/metabolismo , Água/metabolismo , Solventes , Transporte de Elétrons
5.
Mar Drugs ; 20(1)2022 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-35049912

RESUMO

Ericaria crinita and Ericaria amentacea from the Adriatic Sea (Croatia) were investigated with respect to the presence of less-polar compounds for the first time after fractionation by solid-phase extraction (SPE). The composition of less-polar fractions of freeze-dried E. crinita (FdEc) and E. amentacea (FdEa) were analyzed by high-performance liquid chromatography-high-resolution mass spectrometry with electrospray ionization (UHPLC-ESI-HRMS). The major identified compounds were: amides of higher aliphatic acids (palmitoleamide, linoleamide, palmitamide, oleamide and erucamide) and related compounds, carotenoid (fucoxanthin), chlorophyll derivatives (pheophytin a and b and their derivatives) and higher terpenes (loliolide, isoamijiol with its oxidation product), ß-stigmasterol and (3ß,6α)-14-methylergosta-8,24(28)-diene-3,6-diol). The toxic effects observed on the less-polar fractions obtained from Ericaria species on zebrafish Danio rerio embryos could be associated with the high abundance of all five detected amides. The antioxidant activity of the fractions was evaluated by means of five independent assays, including the reduction of the radical cation (ABTS), the oxygen radical absorbance capacity (ORAC), ferric-reducing antioxidant power (FRAP), the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay and the Folin-Ciocalteu method. A higher antioxidant activity of E. amentacea in comparison to that of the E. crinita fractions was found with IC50 concentrations of 0.072 and 1.177 mg/mL, respectively. The correlation between the activity and the chemical composition revealed that the synergistic effect of different compounds impacted their antioxidant response.


Assuntos
Antioxidantes/farmacologia , Toxinas Marinhas/farmacologia , Phaeophyceae , Animais , Antioxidantes/química , Organismos Aquáticos , Bioprospecção , Cromatografia Líquida de Alta Pressão , Croácia , Concentração Inibidora 50 , Toxinas Marinhas/química , Oceanos e Mares , Capacidade de Absorbância de Radicais de Oxigênio , Peixe-Zebra
6.
Molecules ; 27(19)2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36234707

RESUMO

Green teas are nonfermented teas, the quality of which is measured by the green color. However, this category encompasses a high number of tea varieties that differ in cultivation and processing. For example, leaf or stem/bubble tea, plants cultivated under a light or shadow regime, powdered or unpowdered tea, etc. These variables determine the different qualities among green teas (Matcha, Sencha, Gyokuro, etc.) and consequently their different values on the market. Our purpose is to determine if these variables can exert an influence on the chlorophyll profile and to establish a characteristic profile for specific green teas. With such an aim, we analyzed the chlorophyll profiles of 6 different green tea varieties via HPLC-hr ESI/APCI-MS2 and identified up to 17 different chlorophyll compounds. For the first time, 132-hydroxy-chlorophylls, 132-hydroxy-pheophytins, and 151-hydroxy-lactone-pheophytins have been identified in green teas. Shadow teas (Matcha and Sencha) and light-regimen green teas can be statistically differentiated by the total chlorophyll content and the a/b ratio. However, only Matcha tea contains a higher proportion of chlorophylls a and b among the green tea varieties analyzed, justifying the higher quality and price of this variety. Other chlorophyll metabolites (pheophytins, pyropheophytins, and oxidized chlorophylls) are indicative of the various processing and storage conditions.


Assuntos
Feofitinas , Chá , Clorofila/análise , Cromatografia Líquida de Alta Pressão , Lactonas
7.
Bull Environ Contam Toxicol ; 109(3): 450-458, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35437706

RESUMO

Cyanobacteria harmful algal blooms (CyanoHABs) are a global concern. Application of allelochemicals is a promising solution for cyanobacteria control, due to its high efficiency, low cost and ecological safety. Flavonoids (natural polyphenols produced by aquatic plants) are reported capable of effectively inhibiting the growth of algae; however, the molecular mechanism of algae chlorophyll inactivation is still unclear. In this study, quercetin was used as a typical flavonoid, to investigate the inactivation effect of allelochemical on Microcystis aeruginosa chlorophyll a. The absorption and fluorescence spectra showed that chlorophyll reacted with quercetin to form pheophytin, and the formation rate of pheophytin increased with increasing quercetin concentration (1 × 10-5-1 × 10-2 M). FTIR spectra and DFT calculation showed that Mg2+ complexed with the 3-OH and 4-C = O groups in the quercetin ring C so that chlorophyll was inactivated due to the loss of Mg2+ ions. Overall, this study revealed that quercetin inactivated chlorophyll a of cyanobacteria by capturing Mg2+ ions, providing insights into the molecular mechanisms of algal bloom control by allelochemicals.


Assuntos
Cianobactérias , Microcystis , Clorofila , Clorofila A , Proliferação Nociva de Algas , Feofitinas/farmacologia , Feromônios , Plantas/química , Quercetina/toxicidade
8.
J Integr Plant Biol ; 63(10): 1740-1752, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34002536

RESUMO

Photosystem I (PSI) is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin (or cytochrome c6 ) and the reduction of ferredoxin. This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor (a special chlorophyll (Chl) pair) and electron acceptors A0 , A1 , and three Fe4 S4 clusters, FX , FA , and FB . Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3 Å resolution obtained by single-particle cryo-electron microscopy. The A. marina PSI exists as a trimer with three identical monomers. Surprisingly, the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A0 is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures. A novel subunit Psa27 is observed in the A. marina PSI structure. In addition, 77 Chls, 13 α-carotenes, two phylloquinones, three Fe-S clusters, two phosphatidyl glycerols, and one monogalactosyl-diglyceride were identified in each PSI monomer. Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.


Assuntos
Clorofila/metabolismo , Cianobactérias/química , Feofitinas/metabolismo , Complexo de Proteína do Fotossistema I/química , Microscopia Crioeletrônica , Cianobactérias/metabolismo , Cianobactérias/ultraestrutura , Transporte de Elétrons , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema I/ultraestrutura , Estrutura Quaternária de Proteína
9.
Plant J ; 97(6): 1022-1031, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30471153

RESUMO

The STAY-GREEN (SGR) gene encodes Mg-dechelatase which catalyzes the conversion of chlorophyll (Chl) a to pheophytin (Pheo) a. This reaction is the first and most important regulatory step in the Chl degradation pathway. Conversely, Pheo a is an indispensable molecule in photosystem (PS) II, suggesting the involvement of SGR in the formation of PSII. To investigate the physiological functions of SGR, we isolated Chlamydomonas sgr mutants by screening an insertion-mutant library. The sgr mutants had reduced maximum quantum efficiency of PSII (Fv /Fm ) and reduced Pheo a levels. These phenotypes were complemented by the introduction of the Chlamydomonas SGR gene. Blue Native polyacrylamide gel electrophoresis and immunoblotting analysis showed that although PSII levels were reduced in the sgr mutants, PSI and light-harvesting Chl a/b complex levels were unaffected. Under nitrogen starvation conditions, Chl degradation proceeded in the sgr mutants as in the wild type, indicating that ChlamydomonasSGR is not required for Chl degradation and primarily contributes to the formation of PSII. In contrast, in the Arabidopsis sgr triple mutant (sgr1 sgr2 sgrL), which completely lacks SGR activity, PSII was synthesized normally. These results suggest that the Arabidopsis SGR participates in Chl degradation while the ChlamydomonasSGR participates in PSII formation despite having the same catalytic property.


Assuntos
Arabidopsis/enzimologia , Chlamydomonas reinhardtii/enzimologia , Enzimas/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Chlamydomonas reinhardtii/genética , Clorofila/metabolismo , Proteínas de Cloroplastos/genética , Proteínas de Cloroplastos/metabolismo , Enzimas/genética , Mutação , Fenótipo , Feofitinas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo
10.
Microb Pathog ; 141: 104034, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32007619

RESUMO

Efflux pumps are integral parts of the bacterial plasma membrane that are responsible for many cases of antibiotic resistance. Modulators of drug resistance are regarded as the most suitable new antibacterial therapies. We evaluated the extracts of Sargassum polyceratium and the isolated compound pheophytin (Sp-1) for antibiotic modifying activity in strains of Staphylococcus aureus with efflux pump. The minimum inhibitory concentrations (MICs) for norfloxacin, tetracycline and erythromycin were determined by the microdilution broth method, in the absence and presence of the extract at a sub-inhibitory concentration (MIC/4). The extracts and isolated compounds showed no significant antimicrobial activity, but they changed the antibiotic activity, decreasing bacterial resistance by 2 to 4x. Using a checkerboard method, it was also possible to observe the synergistic effect (ΣFIC ≤ 0.5) between Sp-1 and the antibiotics erythromycin and norfloxacin. The results indicate that the seaweed Sargassum polyceratium and pheophytin are potential sources of an antibiotic adjuvant that modulates bacterial resistance, acting as a putative efflux pump inhibitor.


Assuntos
Proteínas Associadas à Resistência a Múltiplos Medicamentos/antagonistas & inibidores , Feofitinas/farmacologia , Sargassum/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Antibacterianos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/metabolismo , Farmacorresistência Bacteriana/efeitos dos fármacos , Sinergismo Farmacológico , Eritromicina/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Testes de Sensibilidade Microbiana , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Norfloxacino/farmacologia , Feofitinas/metabolismo , Extratos Vegetais/farmacologia , Staphylococcus aureus/metabolismo , Tetraciclina/farmacologia
11.
J Environ Manage ; 258: 109989, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929079

RESUMO

The chlorophyll-breakdown to pheophorbide is determined by biotic factors such as grazing (via chlorophyllide) or senescence (via pheophytin). So far, much of the information on chlorophyll-breakdown is available from sediments, but information from the water column is limited. This study addressed chlorophyll-breakdown-pathways (Chl-BP) on a seasonal basis from eight major ports (18-30 stations/port) representing freshwater, estuarine, and marine ecosystems. The distribution of chlorophyll and its breakdown fractions (pheophytin, pheophorbide) exhibited distinct spatial and seasonal variations. Fresh-water (except Haldia-port) and estuarine ports are characterized by high-biomass, high-pheophytin, and low-pheophorbide, whereas marine-ports by low-biomass (except Mangalore-port), low-pheophytin, and high-pheophorbide. Pheophytin and pheophorbide distribution were biomass independent and dependent, respectively. The pheophorbide: pheophytin ratio indicated a potential proxy for determining the dominant breakdown pathway, i.e., herbivory dominant (>1) or not dominant (<1). However, CHl-BP is taxa-specific and grazer's feeding habits. The ratios exhibited apparent differences between different ecosystems, i.e., the higher ratios in marine (up to 11.2) followed by estuarine (up to 0.9) and freshwater (up to 0.4; except Haldia) systems. The diatoms (preferred grazer diet) contribution to total phytoplankton was more in marine followed by estuarine and freshwater systems. The low and high ratios suggested the prevalence of chlorophyll-breakdown via senescence and grazing mode, respectively. We proposed that such scaling will have implications in the ballast water management - BWM (ballast tank conditions (eg. dark) during voyages, post-voyage discharge - including treated water using approved BWM systems, and the nature of ports, potential discharge point) and algal bloom research (e.g. understanding fate and in control measures).


Assuntos
Clorofila , Fitoplâncton , Ecossistema , Eutrofização , Água Doce
12.
Photosynth Res ; 142(1): 69-85, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31172355

RESUMO

Chlorophyll (Chl) breakdown is a diagnostic visual process of leaf senescence, which furnishes phyllobilins (PBs) by the PAO/phyllobilin pathway. As Chl breakdown disables photosynthesis, it appears to have no role in photoactive green leaves. Here, colorless PBs were detected in green, non-senescent leaves of Arabidopsis thaliana. The PBs from the green leaves had structures entirely consistent with the PAO/phyllobilin pathway and the mutation of a single Chl catabolic enzyme completely abolished PBs with the particular modification. Hence, the PAO/phyllobilin pathway was active in the absence of visible senescence and expression of genes encoding Chl catabolic enzymes was observed in green Arabidopsis leaves. PBs accumulated to only sub-% amounts compared to the Chls present in the green leaves, excluding a substantial contribution of Chl breakdown from rapid Chl turnover associated with photosystem II repair. Indeed, Chl turnover was shown to involve a Chl a dephytylation and Chl a reconstitution cycle. However, non-recyclable pheophytin a is also liberated in the course of photosystem II repair, and is proposed here to be scavenged and degraded to the observed PBs. Hence, a cryptic form of the established pathway of Chl breakdown is indicated to play a constitutive role in photoactive leaves.


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Arabidopsis/química , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Senescência Celular , Cromatografia Líquida de Alta Pressão , Regulação da Expressão Gênica de Plantas , Fotossíntese , Folhas de Planta/química , Folhas de Planta/metabolismo
13.
Molecules ; 24(8)2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30999569

RESUMO

BACKGROUND: This study is designed to discover a method for delivering an efficient potent pheophytin a (pheo-a) into more absorbed and small polymeric ethyl cellulose (EC) microparticles. METHODS: Silica gel and Sephadex LH-20 columns were used to isolate pheo-a from the chloroform extract of the edible plant, Suaeda vermiculata. Pheo-a was incorporated into EC microparticles using emulsion-solvent techniques. The antioxidant activity of pheo-a microparticles was confirmed by the level of superoxide radical (SOD), nitric oxide (NO), and reducing power (RP) methods. Meanwhile, the cytotoxic effect of the product was investigated on MCF-7 cells using MTT assay. RESULTS: Pheo-a was isolated from S. vermiculata in a 12% concentration of the total chloroform extract. The structures were confirmed by NMR and IR spectroscopic analysis. The formulated microparticles were uniform, completely dispersed in the aqueous media, compatible as ingredients, and had a mean diameter of 139 ± 1.56 µm as measured by a particle size analyzer. Pheo-a demonstrated a valuable antioxidant activity when compared with ascorbic acid. The IC50 values of pheo-a microparticles were 200.5 and 137.7 µg/mL for SOD, and NO respectively. The reducing power of pheo-a microparticles was more potent than ascorbic acid and had a 4.2 µg/mL for IC50 value. Pheo-a microparticles did not show notable cytotoxicity on the MCF-7 cell line (IC50 = 35.9 µg/mL) compared with doxorubicin (IC50 = 3.2 µg/mL). CONCLUSIONS: the results showed that water-soluble pheo-a microparticles were prepared with a valuable antioxidant activity in a wide range of concentrations with a noteworthy cytotoxic effect.


Assuntos
Antioxidantes , Celulose/análogos & derivados , Chenopodiaceae/química , Portadores de Fármacos , Feofitinas , Antioxidantes/química , Antioxidantes/farmacocinética , Antioxidantes/farmacologia , Celulose/química , Celulose/farmacocinética , Celulose/farmacologia , Portadores de Fármacos/química , Portadores de Fármacos/farmacocinética , Portadores de Fármacos/farmacologia , Humanos , Células MCF-7 , Feofitinas/química , Feofitinas/farmacocinética , Feofitinas/farmacologia
14.
Photosynth Res ; 136(1): 1-16, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28921410

RESUMO

Vyacheslav Vasilevich (V.V.) Klimov (or Slava, as most of us called him) was born on January 12, 1945 and passed away on May 9, 2017. He began his scientific career at the Bach Institute of Biochemistry of the USSR Academy of Sciences (Akademy Nauk (AN) SSSR), Moscow, Russia, and then, he was associated with the Institute of Photosynthesis, Pushchino, Moscow Region, for about 50 years. He worked in the field of biochemistry and biophysics of photosynthesis. He is known for his studies on the molecular organization of photosystem II (PSII). He was an eminent scientist in the field of photobiology, a well-respected professor, and, above all, an outstanding researcher. Further, he was one of the founding members of the Institute of Photosynthesis in Pushchino, Russia. To most, Slava Klimov was a great human being. He was one of the pioneers of research on the understanding of the mechanism of light energy conversion and of water oxidation in photosynthesis. Slava had many collaborations all over the world, and he is (and will be) very much missed by the scientific community and friends in Russia as well as around the World. We present here a brief biography and some comments on his research in photosynthesis. We remember him as a friendly and enthusiastic person who had an unflagging curiosity and energy to conduct outstanding research in many aspects of photosynthesis, especially that related to PSII.


Assuntos
Bioquímica/história , Biofísica/história , História do Século XX , História do Século XXI , Humanos
15.
Molecules ; 23(5)2018 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-29701638

RESUMO

The chlorophyll, pheophytin, and their proportions are critical factors to evaluate the sensory quality of green tea. This research aims to establish an effective method to determine the quantification of chlorophyll and pheophytin in green tea, based on Fourier transform infrared (FT⁻IR) spectroscopy. First, five brands of tea were collected for spectral acquisition, and the chlorophyll and pheophytin were measured using the reference method. Then, a relation between these two pigments and FT⁻IR spectroscopy were developed based on chemometrics. Additionally, the characteristic IR wavenumbers of these pigments were extracted and proved to be effective for a quantitative determination. Successively, non-linear models were also built based on these characteristic wavenumbers, obtaining coefficients of determination of 0.87, 0.80, 0.85 and 0.89; and relative predictive deviations of 2.77, 2.62, 2.26 and 3.07 for the four pigments, respectively. These results demonstrate the feasibility of FT⁻IR spectroscopy for the determination of chlorophyll and pheophytin.


Assuntos
Clorofila/análise , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Chá/química , Dinâmica não Linear , Feofitinas/análise
16.
Environ Monit Assess ; 190(4): 229, 2018 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-29550888

RESUMO

We examined the responses of the phytoplankton and the bacterioplankton of the freshwater zone of the Río de la Plata estuary when exposed to an addition of hexavalent chromium (Cr+6). The planktonic community from a coastal site was exposed to a chromium increase of 80 µg L-1 for 72 h in laboratory conditions. The results showed a decrease in the concentration of Cr+6 by 33% in the treatments, along with significant decreases in chlorophyll-a (63%), the chlorophyll-a:pheophytin-a ratio (33%), oxygen production (37%), and in the total density of the phytoplankton (15%). The relative abundance of chlorophytes and diatoms decreased, while the cyanobacteria thrived. Finally, the total bacterial density and the density of viable bacteria decreased. These results show that even small increments in Cr+6 can cause significant effects on the phytoplankton and bacterioplankton, which could potentially affect other trophic levels of the community, risking alterations of the entire ecosystem.


Assuntos
Cromo/toxicidade , Fitoplâncton/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Clorofila/metabolismo , Clorofila A , Diatomáceas/efeitos dos fármacos , Diatomáceas/metabolismo , Monitoramento Ambiental/métodos , Estuários , Oxigênio/metabolismo , Fitoplâncton/metabolismo , Fitoplâncton/fisiologia
17.
Int J Mol Sci ; 18(12)2017 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-29211014

RESUMO

Sepsis is an overwhelming systemic response to infection that frequently results in tissue damage, organ failure, and even death. Nitric oxide (NO), prostaglandin E2 (PGE2), and cytokine overproduction are thought to be associated with the immunostimulatory cascade in sepsis. In the present study, we analyzed the anti-inflammatory efficacy of the pheophytin-b on both RAW 264.7 murine macrophage and purified human CD14⁺ monocytes stimulated with lipopolysaccharide (LPS) and elucidated the mechanisms by analyzing the cell signaling pathways known to be activated in sepsis. Pheophytin-b suppressed the overexpression of NO, PGE2, and cytokines in LPS-stimulated macrophages without inducing cytotoxicity. It also reduced NOS2 and COX-2 mRNA and protein levels. The inhibitory effects on NO, PGE2, and cytokine overproduction arose from the suppression of STAT-1 and PI3K/Akt pathways; no changes in NF-κB, MAPK, and AP-1 signaling were detected. Thus, pheophytin-b may represent a potential candidate to beneficially modulate the inflammatory response in sepsis.


Assuntos
Anti-Inflamatórios/farmacologia , Citocinas/metabolismo , Dinoprostona/metabolismo , Macrófagos/efeitos dos fármacos , Óxido Nítrico/metabolismo , Feofitinas/farmacologia , Animais , Linhagem Celular , Células Cultivadas , Citocinas/genética , Humanos , Lipopolissacarídeos/toxicidade , Macrófagos/metabolismo , Camundongos , Transdução de Sinais
18.
Molecules ; 22(11)2017 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-29113139

RESUMO

Ocimum plants are traditionally used to manage HIV/AIDS in various African countries. The effects of Ocimum labiatum extract on HIV-1 protease (PR) and reverse transcriptase (RT) is presented here along with characterization of an identified bioactive compound, achieved through ¹H- and 13C-NMR. The extract's effect on HIV-1 replication was assessed by HIV-1 p24 antigen capture. Cytotoxicity of samples was evaluated using tetrazolium dyes and real-time cell electronic sensing (RT-CES). Ocimum labiatum inhibited HIV-1 PR with an IC50 value of 49.8 ± 0.4 µg/mL and presented weak inhibition (21%) against HIV-1 RT. The extract also reduced HIV-1 replication in U1 cells at a non-cytotoxic concentration (25 µg/mL). The CC50 value of the extract in U1 cells was 42.0 ± 0.13 µg/mL. The HIV-1 PR inhibiting fraction was purified using prep-HPLC and yielded a chlorophyll derivative, pheophytin-a (phy-a). Phy-a inhibited HIV-1 PR with an IC50 value of 44.4 ± 1.5 µg/mL (51 ± 1.7 µM). The low cytotoxicity of phy-a in TZM-bl cells was detected by RT-CES and the CC50 value in U1 cells was 51.3 ± 1.0 µg/mL (58.9 ± 1.2 µM). This study provides the first in vitro evidence of anti-HIV activity of O. labiatum and isolated phy-a, supporting further investigation of O. labiatum for lead compounds against HIV-1.


Assuntos
Fármacos Anti-HIV/farmacologia , HIV-1/fisiologia , Ocimum/química , Feofitinas/farmacologia , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Viral da Expressão Gênica/efeitos dos fármacos , Protease de HIV/genética , Inibidores da Protease de HIV , Transcriptase Reversa do HIV/genética , HIV-1/efeitos dos fármacos , HIV-1/enzimologia , HIV-1/genética , Estrutura Molecular , Feofitinas/química , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Espectroscopia de Prótons por Ressonância Magnética , Inibidores da Transcriptase Reversa , Replicação Viral/efeitos dos fármacos
19.
Photosynth Res ; 130(1-3): 445-467, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27334004

RESUMO

In this review, we introduce our recent studies on divinyl chlorophylls functioning in unique marine picoplankton Prochlorococcus sp. (1) Essential physicochemical properties of divinyl chlorophylls are compared with those of monovinyl chlorophylls; separation by normal-phase and reversed-phase high-performance liquid chromatography with isocratic eluent mode, absorption spectra in four organic solvents, fluorescence information (emission spectra, quantum yields, and life time), circular dichroism spectra, mass spectra, nuclear magnetic resonance spectra, and redox potentials. The presence of a mass difference of 278 in the mass spectra between [M+H]+ and the ions indicates the presence of a phytyl tail in all the chlorophylls. (2) Precise high-performance liquid chromatography analyses show divinyl chlorophyll a' and divinyl pheophytin a as the minor key components in four kinds of Prochlorococcus sp.; neither monovinyl chlorophyll a' nor monovinyl pheophytin a is detected, suggesting that the special pair in photosystem I and the primary electron acceptor in photosystem II are not monovinyl but divinyl-type chlorophylls. (3) Only Prochlorococcus sp. NIES-2086 possesses both monovinyl chlorophyll b and divinyl chlorophyll b, while any other monovinyl-type chlorophylls are absent in this strain. Monovinyl chlorophyll b is not detected at all in the other three strains. Prochlorococcus sp. NIES-2086 is the first example that has both monovinyl chlorophyll b as well as divinyl chlorophylls a/b as major chlorophylls.


Assuntos
Clorofila/fisiologia , Prochlorococcus/química , Clorofila/análise , Clorofila/química , Estrutura Molecular , Prochlorococcus/fisiologia
20.
J Appl Microbiol ; 121(6): 1592-1602, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27699961

RESUMO

AIMS: This investigation is designed to evaluate the antibacterial efficiency of the noodle grass Syringodium isoetifolium, which is commonly found in the Indian coastal waters. Also, this study characterizes the active compound and predicts the mode of action in silico. METHODS AND RESULTS: Human pathogenic bacteria were treated with crude metabolites of S. isoetifolium. The potent fraction b was analysed by UV/VIS, Spectroscopy RP-HPLC, FT-IR, ESI-Mass and 1 H and 13 C NMRs and determined to be a hydrate of pheophytin a (C55 H74 N4 O6 ). The isolated compound Pheo had MIC values of 6·2 ± 0·7 (Salmonella typhi) and 12·5 ± 0·8 (Escherichia coli and Pseudomonas aeruginosa) µg ml-1 . Molecular docking studies of the compound were done to find the binding sites on the pathogens using a Molegro Virtual Docker platform. Pheo targets umuC proteins by binding compactly to five amino acid residues with interaction energy of -3·66 and a Moldock score of -160·175. CONCLUSIONS: Hence, we conclude that pheophytin a, besides being an accessory photosynthetic pigment, also has proven to be antibacterial against human pathogens. Lesser MIC values with definite binding sites predicted in silico are suggestive of a precise of action for this compound. SIGNIFICANCE AND IMPACT OF THE STUDY: Easy extraction methods of the active compound that has a definite target render this under-explored seagrass a good source of antibacterial compound against human pathogenic bacteria. This learning may favour more researches in this unexplored area to build up Pheo-based natural products as antibiotic therapies.


Assuntos
Alismatales/química , Antibacterianos/farmacologia , Proteínas de Bactérias/química , Feofitinas/farmacologia , Antibacterianos/química , Antibacterianos/isolamento & purificação , Proteínas de Bactérias/antagonistas & inibidores , Simulação por Computador , DNA Polimerase Dirigida por DNA/química , Escherichia coli/efeitos dos fármacos , Proteínas de Escherichia coli/química , Simulação de Acoplamento Molecular , Feofitinas/química , Feofitinas/isolamento & purificação , Pseudomonas aeruginosa/efeitos dos fármacos , Salmonella typhi/efeitos dos fármacos
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