Molecular characterization of a flavanone 3-hydroxylase gene from citrus fruit reveals its crucial roles in anthocyanin accumulation.

BACKGROUND: Flavanone 3-hydroxylase (F3H), a key enzyme in the flavonoid biosynthetic pathway, plays an important role in the regulation of flavonols and anthocyanidins accumulation. Citrus fruit is a rich source of flavonoids with varied flavonoid compositions among different varieties. To date, the study on F3H is limited in citrus, and its roles in regulating flavonoid accumulation in citrus fruit are still unclear. RESULTS: In this study, we isolated a CitF3H from three different citrus varieties, Satsuma mandarin (Citrus unshiu Marc.), Ponkan mandarin (C. reticulata Blanco) and blood orange 'Moro' (C. sinensis Osbeck). Functional analysis showed that CitF3H encoded a functional flavanone 3-hydroxylase. It catalyzed the hydroxylation of naringenin to yield dihydrokaempferol, which was a precursor of anthocyanins in flavonoid biosynthetic pathway. In the juice sacs, CitF3H was differentially expressed among the three citrus varieties, and its expression level was positively correlated with the accumulation of anthocyanins during the ripening process. In the juice sacs of Satsuma mandarin and Ponkan mandarin the expression of CitF3H kept constant at an extremely low level, and no anthocyanin was accumulated during the ripening process. In contrast, the expression of CitF3H increased rapidly along with the accumulation of anthocyanin in the juice sacs of blood orange 'Moro' during the ripening process. In addition, we found that blue light irradiation was effective to up-regulate the expression of CitF3H and improve anthocyanin accumulation in the juice sacs of blood orange 'Moro' in vitro. CONCLUSION: CitF3H was a key gene regulating anthocyanin accumulation in the juice sacs of citrus fruit. The results presented in this study will contribute to elucidating anthocyanin biosynthesis in citrus fruit, and provide new strategies to improve the nutritional and commercial values of citrus fruit.

Two New Preyssler-Type Polyoxometalate-Based Coordination Polymers and Their Application in Horseradish Peroxidase Immobilization.

Enzyme immobilization is of increasing importance for biocatalysis, for which good supports are critical. Herein, two new Preyssler-type polyoxometalate (POM)-based coordination polymers, namely, {[Cu(H2 biim)2 ][{Cu(H2 biim)2 (µ-H2 O)}2 Cu(H2 biim)(H2 O)2 ]H[({Cu(H2 biim)(H2 O)2 }0.5 )2 ((µ-C3 HN2 Cl2 ){Cu(H2 biim)}2 ){Z(H2 O)P5 W30 O110 }]⋅x H2 O}n (1: Z=Na, x=9; 2: Z=Ag, x=10; H2 biim=2,2'-biimidazole) were designed and synthesized. Compounds 1 and 2 exhibit the same skeletons, which contain multiple CuII complex fragments and penta-supported {ZP5 W30 } (Z=Na, Ag) clusters. They were first employed to immobilize horseradish peroxidase (HRP). Results show that compounds 1 and 2 are good supports for HRP immobilization, and exhibit higher enzyme loading, lower loading times, and excellent reusability. The immobilized HRP (HRP/1 or HRP/2) was further applied to detect H2 O2 , and good sensitivity, wide linear range, low detection limit, and fast response were achieved. This work shows that POM-based hybrid materials are a new kind of promising support for enzyme immobilization.

Expression and functional analysis of citrus carotene hydroxylases: unravelling the xanthophyll biosynthesis in citrus fruits.

BACKGROUND: Xanthophylls are oxygenated carotenoids and fulfill critical roles in plant growth and development. In plants, two different types of carotene hydroxylases, non-heme di-iron and heme-containing cytochrome P450, were reported to be involved in the biosynthesis of xanthophyll. Citrus fruits accumulate a high amount of xanthophylls, especially ß,ß-xanthophylls. To date, however, the roles of carotene hydroxylases in regulating xanthophyll content and composition have not been elucidated. RESULTS: In the present study, the roles of four carotene hydroxylase genes (CitHYb, CitCYP97A, CitCYP97B, and CitCYP97C) in the biosynthesis of xanthophyll in citrus fruits were investigated. Phylogenetic analysis showed that the four citrus carotene hydroxylases presented in four distinct clusters which have been identified in higher plants. CitHYb was a non-heme di-iron carotene hydroxylase, while CitCYP97A, CitCYP97B, and CitCYP97C were heme-containing cytochrome P450-type carotene hydroxylases. Gene expression results showed that the expression of CitHYb increased in the flavedo and juice sacs during the ripening process, which was well consistent with the accumulation of ß,ß-xanthophyll in citrus fruits. The expression of CitCYP97A and CitCYP97C increased with a peak in November, which might lead to an increase of lutein in the juice sacs during the ripening process. The expression level of CitCYP97B was much lower than that of CitHYb, CitCYP97A, and CitCYP97C in the juice sacs during the ripening process. Functional analysis showed that the CitHYb was able to catalyze the hydroxylation of the ß-rings of ß-carotene and α-carotene in Escherichia coli BL21 (DE3) cells. Meanwhile, when CitHYb was co-expressed with CitCYP97C, α-carotene was hydroxylated on the ß-ring and ε-ring sequentially to produce lutein. CONCLUSIONS: CitHYb was a key gene for ß,ß-xanthophyll biosynthesis in citrus fruits. CitCYP97C functioned as an ε-ring hydroxylase to produce lutein using zeinoxanthin as a substrate. The results will contribute to elucidating xanthophyll biosynthesis in citrus fruits, and provide new strategies to improve the nutritional and commercial qualities of citrus fruits.

Enzymatic formation of ß-citraurin from ß-cryptoxanthin and Zeaxanthin by carotenoid cleavage dioxygenase4 in the flavedo of citrus fruit.

In this study, the pathway of ß-citraurin biosynthesis, carotenoid contents and the expression of genes related to carotenoid metabolism were investigated in two varieties of Satsuma mandarin (Citrus unshiu), Yamashitabeni-wase, which accumulates ß-citraurin predominantly, and Miyagawa-wase, which does not accumulate ß-citraurin. The results suggested that CitCCD4 (for Carotenoid Cleavage Dioxygenase4) was a key gene contributing to the biosynthesis of ß-citraurin. In the flavedo of Yamashitabeni-wase, the expression of CitCCD4 increased rapidly from September, which was consistent with the accumulation of ß-citraurin. In the flavedo of Miyagawa-wase, the expression of CitCCD4 remained at an extremely low level during the ripening process, which was consistent with the absence of ß-citraurin. Functional analysis showed that the CitCCD4 enzyme exhibited substrate specificity. It cleaved ß-cryptoxanthin and zeaxanthin at the 7,8 or 7',8' position. But other carotenoids tested in this study (lycopene, α-carotene, ß-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin) were not cleaved by the CitCCD4 enzyme. The cleavage of ß-cryptoxanthin and zeaxanthin by CitCCD4 led to the formation of ß-citraurin. Additionally, with ethylene and red light-emitting diode light treatments, the gene expression of CitCCD4 was up-regulated in the flavedo of Yamashitabeni-wase. These increases in the expression of CitCCD4 were consistent with the accumulation of ß-citraurin in the two treatments. These results might provide new strategies to improve the carotenoid contents and compositions of citrus fruits.

Self-assembly of a unique triangle-like tungstovanadate containing pentagonal {(WO7)W3(SnR)2} cluster.

In aqueous solution, a novel triangle-like tungstovanadate estertin derivative K10H10.5[(W4O15(H2O)2){(SnCH2CH2COO)2(V0.75W10.75/V0.25O39)}{{(SnCH2CH2COO)2(µ-OH)}2(SnCH2CH2COO)(VW10O37)}2]·31H2O ((SnR)8-V3W35, R = CH2CH2COO) was assembled by a conventional synthetic method. (SnR)8-V3W35 is composed of one [VW11O39]7- ({VW11}) and two [VW10O37]9- ({VW10}) units connected by eight [Sn(CH2)2COO]2+ groups and a {W4O19} cluster. Interestingly, there exists a pentagonal bipyramid WO7 polyhedral center surrounded by two SnCO5 and three WO6 octahedra, forming a pentagonal {(WO7)W3(SnR)2} cluster in this polyoxometalate (POM), which is also the first example of a pentagonal structure formed by transition metals (TMs) and main group organometals in the POM family. Furthermore, the structure of this organic-inorganic hybrid POM also exhibits the largest number of organotin groups introduced into the POM system. It was characterized with various physico-chemical and spectroscopic methods, including X-ray single crystal and powder diffraction analysis, 119Sn and 51V NMR, IR, thermal gravimetric analysis (TGA), etc. In addition, the catalytic activity of (SnR)8-V3W35 as a mimic of peroxidase was evaluated using o-phenylenediamine (OPD) as a peroxidase substrate. The major factors influencing the oxidation reaction such as pH, the dosage of (SnR)8-V3W35, and concentrations of OPD and H2O2 were mainly studied. (SnR)8-V3W35 exhibits good peroxidase-like catalytic activity. From another perspective, the successful acquisition of (SnR)8-V3W35 further proves the instability and easy reassembly characteristics of TM-sandwich-type tungstovanadates, which also provides a new assembly strategy for synthesizing POM-estertin derivatives.

Expression and functional analysis of two lycopene ß-cyclases from citrus fruits.

In the present study, two LCYb genes (CitLCYb1 and CitLCYb2) were isolated from Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck) and Lisbon lemon (Citrus limon Burm.f.) and their functions were analyzed by the color complementation assay in lycopene-accumulating E. coli cells. The results showed that CitLCYb1 and CitLCYb2 shared high identity at the amino acid level among the three citrus varieties. The N-terminal region of the two proteins encoded by CitLCYb1 and CitLCYb2 was predicted to contain a 51-residue chloroplastic transit peptide, which shared low similarity. In Satsuma mandarin, the secondary structures of the CitLCYb1 and CitLCYb2 encoding proteins without the transit peptide were quite similar. Moreover, functional analysis showed that both enzymes of CitLCYb1 and CitLCYb2 participated in the formation of ß-carotene, and when they were co-expressed with CitLCYe, α-carotene could be produced from lycopene in E. coli cells. However, although CitLCYb2 could convert lycopene to α-carotene in E. coli cells, its extremely low level of expression indicated that CitLCYb2 did not participate in the formation of α-carotene during the green stage in the flavedo. In addition, the high expression levels of CitLCYb1 and CitLCYb2 during the orange stage played an important role in the accumulation of ß,ß-xanthophylls in citrus fruits. The results presented in this study might contribute to elucidate the mechanism of carotenoid accumulation in citrus fruits.

Regulation of carotenoid accumulation and the expression of carotenoid metabolic genes in citrus juice sacs in vitro.

In the present study, to investigate the mechanisms regulating carotenoid accumulation in citrus, a culture system was set up in vitro with juice sacs of three citrus varieties, Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck), and Lisbon lemon (Citrus limon Burm.f.). The juice sacs of all the three varieties enlarged gradually with carotenoid accumulation. The changing patterns of carotenoid content and the expression of carotenoid metabolic genes in juice sacs in vitro were similar to those ripening on trees in the three varieties. Using this system, the changes in the carotenoid content and the expression of carotenoid metabolic genes in response to environmental stimuli were investigated. The results showed that carotenoid accumulation was induced by blue light treatment, but was not affected by red light treatment in the three varieties. Different regulation of CitPSY expression, which was up-regulated by blue light while unaffected by red light, led to different changes in carotenoid content in response to these two treatments in Satsuma mandarin and Valencia orange. In all three varieties, increases in carotenoid content were observed with sucrose and mannitol treatments. However, the accumulation of carotenoid in the two treatments was regulated by distinct mechanisms at the transcriptional level. With abscisic acid (ABA) treatment, the expression of the genes investigated in this study was up-regulated in Satsuma mandarin and Lisbon lemon, indicating that ABA induced its own biosynthesis at the transcriptional level. This feedback regulation of ABA led to decreases in carotenoid content. With gibberellin (GA) treatment, carotenoid content was significantly decreased in the three varieties. Changes in the expression of genes related to carotenoid metabolism varied among the three varieties in response to GA treatment. These results provided insights into improving carotenoid content and composition in citrus during fruit maturation.

Exogenous gibberellin induced regreening through the regulation of chlorophyll and carotenoid metabolism in Valencia oranges.

In the present study, we studied the effects of gibberellic acid (GA) on chlorophyll and carotenoid metabolites and related gene expression during the regreening process in Valencia orange fruits (Citrus sinensis Osbeck). During the regreening, fruits treated with GA turned green much faster than those of the control. Compared with untreated fruits, chlorophyll accumulation was induced and the content of carotenoids (ß-cryptoxanthin, all-trans-violaxanthin, and 9-cis-violaxanthin) was decreased by the GA treatment. Chlorophyll and carotenoid contents following GA treatment appeared to be highly regulated at the gene transcription level. Correspondingly, the up-regulation of chlorophyll biosynthesis genes (CitGGDR, CitCHL27, CitPORA, and CitCAO) and down-regulation of degradation genes (CitCLH1, CitSGR, CitPPH, CitPAO, and CitRCCR) led to the increase of chlorophyll contents, and the down-regulation of carotenoid biosynthesis genes (CitPSY, CitPDS, CitZDS, CitLCYb2, and CitHYb) led to the decrease of carotenoid contents. These observations indicated that GA acted as a crucial regulator in the regreening process of citrus fruits.

Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Polyoxometalate-Estertin Derivatives.

The development of acid-resistant and efficient corrosion inhibitors is of great significance for metal protection in many industrial processes. In this work, eight cases of sandwich-type polyoxometalate (POM)-based inorganic-organic hybrids, namely, carboxyethyltin and transition metal (TM) cofunctionalized tungstoantimonates and tungstobismuthates, formulated as Na x K10-x [(SnR)2(TM(H2O)3)2(B-ß-SbW9O33)2]·mH2O and Na y K10-y [(SnR)2(TM(H2O)3)2(B-ß-BiW9O33)2]·nH2O (abbreviated as SbW9-TM-SnR and BiW9-TM-SnR; TM = Mn, Co, Ni, and Zn; m = 18, 24, 24, and 22; n = 30, 25, 20, and 21; SnR = Sn(CH2CH2COO)) are first used as green corrosion inhibitors for 20# carbon steel in 0.5-2.0 M HCl solutions. Weight loss and electrochemical experiments prove that the corrosion inhibition efficiency is all above 81% for these POM-based corrosion inhibitors at 150 mg L-1, and SbW9-Mn-SnR shows the highest efficiency of 96.9% at 150 mg L-1 after immersion in a 0.5 M HCl solution for 10 h. Scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses show that these POM-based inhibitors form films on the carbon steel and the adsorption mechanism obeys the Langmuir adsorption model. The thermodynamic activation parameters were calculated, proving the occurrence of both chemical and physical adsorptions. The film-forming mechanism was also analyzed. This work provides guidance for synthesizing new lacunary POM-based materials to protect metals from corrosion in HCl pickling.

Characterization of a Caffeic Acid 8-O-Methyltransferase from Citrus and Its Function in Nobiletin Biosynthesis.

Nobiletin (3',4',5,6,7,8-hexamethoxyflavone) is a polymethoxylated flavonoid specifically accumulated in citrus fruit with numerous beneficial effects to human health. In this study, a novel O-methyltransferase (CitOMT2) was isolated from three citrus varieties, Ponkan mandarin (Citrus reticulata Blanco), Nou 6 ("King mandarin" × "Mukaku-kishu"), and Satsuma mandarin (Citrus unshiu Marc.), and its functions were characterized in vitro. The gene expression results showed that CitOMT2 was highly expressed in the two nobiletin abundant varieties of Ponkan mandarin and Nou 6. However, the expression level of CitOMT2 was low in the flavedo of Satsuma mandarin, in which only a small amount of nobiletin was accumulated. Functional analysis suggested that CitOMT2 was a caffeic acid 8-O-methyltransferase, and it catalyzed the O-methylation of 7,8-dihydroxyflavone at 8-OH. As the methylation of flavone at 8-OH was required for nobiletin biosynthesis, the results presented in this study suggested that CitOMT2 was a key gene regulating nobiletin accumulation in citrus fruit.

Exogenous Application of ABA and NAA Alleviates the Delayed Coloring Caused by Puffing Inhibitor in Citrus Fruit.

Combined spraying of gibberellin (GA) and prohydrojasmon (PDJ) was an effective method to reduce peel puffing in Satsuma mandarins. However, in the GA-and-PDJ combined treatment, fruit color development was delayed during the ripening process. In the present study, to improve the coloration of the GA and PDJ-treated fruit, the effects of exogenous application of 1-naphthaleneacetic acid (NAA) and abscisic acid (ABA) on chlorophyll and carotenoid accumulation were investigated. The results showed that both ABA and NAA treatments accelerated the color changes from green to orange in the GA and PDJ-treated fruit during the ripening process. With the NAA and ABA treatments, chlorophylls contents were decreased rapidly, and the contents of ß,ß-xanthophylls were significantly enhanced in the GA and PDJ-treated fruit. In addition, gene expression results showed that the changes of the chlorophyll and carotenoid metabolisms in the NAA and ABA treatments were highly regulated at the transcriptional level. The results presented in this study suggested that the application of NAA and ABA could potentially be used for improving the coloration of the GA and PDJ-treated fruit.

A POM-based copper-coordination polymer crystal material for phenolic compound degradation by immobilizing horseradish peroxidase.

A new polyoxometalate (POM)-based organic-inorganic hybrid Cu-coordination polymer, namely {((Cu(bipy))2(µ-PhPO3)2Cu(bipy))2H(PCuW11O39)·3H2O}n (denoted as compound 1, bipy = 2,2'-bipyridine, PhPO3 = phenylphosphonate), was self-assembled hydrothermally. Single-crystal X-ray diffraction (SC-XRD) analysis shows that two unique types of 1D chains are present in compound 1, i.e. Cu(II)-organophosphine and organonitrogen complex cation ([((Cu(bipy))2(µ-PhPO3)2Cu(bipy))2]4+) chains and Cu-monosubstituted Keggin-type polyoxoanion ([PCuW11O39]5-) chains, forming a hetero-POM. Crystalline compound 1 as a new enzyme immobilization support exhibited a high horseradish peroxidase (HRP) loading capacity (268 mg g-1). The powder X-ray diffraction (PXRD), FTIR, zeta potential, confocal laser scanning microscopy (CLSM) and circular dichroism (CD) results show that HRP is only immobilized on the surface of compound 1 through simple physical adsorption without a secondary structure change. This POM-immobilized enzyme (HRP/1) was first used for degradation of pollutants in wastewater, and it showed a high degradation efficiency and TOC removal efficiency for phenol, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) within 30 min reaction time. Moreover, HRP/1 exhibited better operational and storage stabilities and reusability compared with free HRP. This work suggests that POMs can be used as new supports for enzyme immobilization and POM-immobilized enzymes may be used as a new kind of biocatalyst for degradation of phenolic pollutants.

Blue LED light induces regreening in the flavedo of Valencia orange in vitro.

In the present study, the effects of blue LED light on the regreening of citrus fruit were investigated in an in vitro system of Valencia orange flavedos. The results showed that blue LED light irradiation induced regreening in the flavedos. After four-week culture in vitro, the flavedos exhibited obviously green color in the blue LED light treatment, while the flavedos in the control were still in orange color. During the regreening process, the blue LED light treatment induced chlorophyll accumulation, and substantially altered the carotenoid composition in the flavedos. Compared with the control, the content of 9-cis-violaxanthin was decreased, while the contents of lutein, ß-carotene, and all-trans-violaxanthin were increased by blue LED light. In addition, gene expression results showed that the up-regulation of CitLCYe and down-regulation of CitLCYb2 by blue LED light led to a shift from ß,ß-branch to ß,ε-branch of the carotenoid biosynthetic pathway.

Expression and functional analysis of the nobiletin biosynthesis-related gene CitOMT in citrus fruit.

Nobiletin, a polymethoxy flavone (PMF), is specific to citrus and has been reported to exhibit important health-supporting properties. Nobiletin has six methoxy groups at the 3',4',5,6,7,8-positions, which are catalyzed by O-methyltransferases (OMTs). To date, researches on OMTs in citrus fruit are still limited. In the present study, a novel OMT gene (CitOMT) was isolated from two citrus varieties Satsuma mandarin (Citrus unshiu Marc.) and Ponkan mandarin (Citrus reticulata Blanco), and its function was characterized in vitro. The results showed that the expression of CitOMT in the flavedo of Ponkan mandarin was much higher than that of Satsuma mandarin during maturation, which was consistent with the higher accumulation of nobiletin in Ponkan mandarin. In addition, functional analysis showed that the recombinant protein of CitOMT had methylation activity to transfer a methyl group to 3'-hydroxy group of flavones in vitro. Because methylation at the 3'-position of flavones is vital for the nobiletin biosynthesis, CitOMT may be a key gene responsible for nobiletin biosynthesis in citrus fruit. The results presented in this study will provide new strategies to enhance nobiletin accumulation and improve the nutritional qualities of citrus fruit.

Two new estertin modified tungstosilicates: synthesis, catalytic activity and photoelectrochemical property.

Two new tungstosilicates (C(NH2)3)5KNa2H3[Sn(CH2CH2COOCH3)Co(H2O)2Si2W19O69]·10H2O (Si2W19-Co-SnRCOOCH3) and (C(NH2)3)5KNa2H3[Sn(CH2CH2COOCH3)Mn(H2O)2Si2W19O69]·13H2O (Si2W19-Mn-SnRCOOCH3) modified by organometal (OM) and transition metal (TM) ions were obtained, and they were self-assembled from mono-TM-containing (TM = Co, Mn) γ-[SiW10O35]6- (γ-SiW10)-based dimeric tungstosilicate and estertin Cl3SnCH2CH2COOCH3 in an acetate buffer solution, respectively. Their structures were determined with a series of physico-chemical and spectroscopic methods including X-ray crystallography, XRPD, etc. The estertin functional position in the tungstosilicate skeleton was analyzed by theoretical calculations using density functional theory (DFT). These two compounds have good catalytic activity for the oxidation of cyclohexanol to cyclohexanone. Meanwhile, they were composited with TiO2 using a facial layer-by-layer (LBL) method. The assembled composite films {Si2W19-TM-SnRCOOCH3/TiO2}n (TM = Co, Mn; n is the bilayer number, n = 1-6) exhibit efficient photoelectrocatalytic activity for the oxidation of methanol under irradiation of 100 mW cm-2 using a Xe lamp as a light source. And the {Si2W19-Co-SnRCOOCH3/TiO2}4 film produces the highest photocurrent among the composite films studied in this work. Combining the dark current measurement, surface photovoltage spectroscopy (SPV) and electrochemical impedance spectroscopy (EIS), the enhanced photoelectrocatalytic activity of {Si2W19-Co-SnRCOOCH3/TiO2}4 composite film for the oxidation of methanol is attributed to the suppressed electron-hole recombination, increased carrier separation efficiency and interfacial charge transfer.

Carboxyethyltin and transition metal co-functionalized tungstoantimonates composited with polypyrrole for enhanced electrocatalytic methanol oxidation.

Carboxyethyltin and first-row transition metals (TMs) were firstly introduced into trivacant Keggin-type tungstoantimonate in an aqueous solution, leading to the formation of four crystalline organic-inorganic hybrid sandwich-type polyoxometalates (POMs), formulated as Na10-x-yKyHx[((TM)(H2O)3)2(Sn(CH2)2COO)2(SbW9O33)2]·nH2O (SbW9-TM-SnR, TM = Mn, Co, Ni, Zn; x = 1, 1, 0, 0; y = 0, 5, 5, 2; n = 18, 24, 24, 22, respectively). SbW9-TM-SnR exhibit high catalytic ability for the oxidation of cyclohexanol. Meanwhile, SbW9-TM-SnR were composited with polypyrrole (PPy) through an electropolymerization process, forming PPy-SbW9-TM-SnR, on which platinum (Pt) was further electro-deposited to prepare PPy-SbW9-TM-SnR/Pt for electrocatalytic methanol (CH3OH) oxidation in acid solution. The composition and morphology of PPy-SbW9-TM-SnR/Pt were determined by IR, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The electrochemical experimental results show that SbW9-TM-SnR and PPy obviously enhance the electrocatalytic and anti-intoxication abilities of Pt, and the highest peak current density of 0.87 mA cm-2, corresponding to 1.85 and 1.43 times higher than those of pure Pt and PPy/Pt electrodes respectively, is acquired for the PPy-SbW9-Ni-SnR/Pt composite electrode. These findings may enlarge the application of PPy and POMs in the electrocatalytic field.

Investigations of the cytotoxicity of epigallocatechin-3-gallate against PC-3 cells in the presence of Cd2+ in vitro.

The epidemiological studies and recent data have provided convinced evidence that green tea and its major constituent epigallocatechin gallate (EGCG) might have the potential to lower the risk of cancers in humans. Metal ions, such as zinc and cadmium, which are necessary to our health, are important factors inducing many diseases including prostate cancer in the condition of absence or excess. EGCG can satisfactorily exhibit complex chemistry with metal ions because of multiple hydroxyl states, which in turn changes their bioactivities and metabolism pathways. This paper presents the results of an investigation of the cytotoxicity of EGCG against PC-3 prostate cancer cells in the presence and absence of Cd2+ in vitro. The results showed that both EGCG and Cd2+ suppressed viability and clonegenecity of PC-3 cells, and the suppression effect was enhanced when EGCG added with Cd2+. Although Cd2+ up-regulated the 67 kDa laminin receptor (67LR), which is a migration-associated protein, the cell migration ability was not significantly increased after each treatment. We also found that EGCG and Cd2+ directly interacted with mitochondrial, and the mixture of EGCG and Cd2+ (EGCG+Cd2+) significantly caused loss of the mitochondrial membrane potential, decrease of the ATP content and activation of caspase-9 compared with EGCG treated alone. Taken together, these findings suggest that Cd2+ enhanced the cytotoxicity of EGCG to PC-3 cells by up-regulating the 67LR and the mitochondria-mediated apoptosis pathway.

Diaqua-bis(2,2'-biimidazole)cobalt(II) dichloride.

There are independent cations and four chloride anions in the crystal structure of the title complex, [Co(C(6)H(6)N(4))(2)(H(2)O)(2)]Cl(2). In each cation, the Co(II) cation is coordinated by four N atoms from two biimidazole and two O atoms of two water mol-ecules; one Co atom is at a position of site symmetry m, the other at a position of site symmetry 2/m. All Cl(-) ions and water mol-ecules are also located on the mirror plane. Each structural unit is connected through O-H⋯Cl and N-H⋯Cl inter-molecular hydrogen bonds, forming a three-dimensional supramolecular structure.

2-(1,3-Dithian-2-yl-idene)-1-phenyl-butane-1,3-dione.

The title compound, C(13)H(12)O(2)S(2), belonging to the group of dioxoketene cyclic S,S-acetals, was prepared from the corresponding dione in high yield. In the structure, the C=O and C=C bonds are not coplanar, with O=C-C=C torsion angles of -36.8 (4) and -21.0 (4)°. The dithian ring has a twisted conformation.

Accumulation of carotenoids in a novel citrus cultivar 'Seinannohikari' during the fruit maturation.

In the present study, carotenoid metabolism was investigated in the fruits of a novel citrus cultivar, 'Seinannohikari' (Citrus spp.). During the maturation, ß,ß-xanthophylls were accumulated rapidly with ß-cryptoxanthin being the dominant carotenoid compound in the flavedo and juice sacs of 'Seinannohikari'. In the juice sacs of mature fruits, 'Seinannohikari' accumulated high amount of carotenoids, especially ß-cryptoxanthin. The content of ß-cryptoxanthin in the juice sacs of 'Seinannohikari' was approximately 2.5 times of that in 'Miyagawa-wase' (Citrus unshiu), which is one of its parental cultivars, at the mature stage. Gene expression results showed that the massive accumulation of ß-cryptoxanthin might be attributed to the higher expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, CitHYb, and CitZEP), and lower expression of carotenoid catabolic genes (CitNCED2 and CitNCED3) in the juice sacs of 'Seinannohikari'.