Improvement of electrocatalytic water oxidation activity of novel copper complex by modulating the axial coordination of phosphate on metal center.

The structure of organic ligand scaffolds of copper complexes critically affects their electrocatalytic properties toward water oxidation, which is widely regarded as the bottleneck of overall water splitting. Herein, two novel mononuclear Cu complexes, [Cu(dmabpy)](ClO4)2 (1, dmabpy = 6,6'-bis(dimethylaminomethyl)-2,2'-bipyridine) and [Cu(mabpy)](ClO4)2 (2, mabpy = 6,6'-bis(methylaminomethyl)-2,2'-bipyridine), with four-coordinated distorted planar quadrilateral geometry were synthesized and explored as efficient catalysts for electrochemical oxygen evolution in phosphate buffer solution. Interestingly, complex 1 with a tertiary amine group catalyzes water oxidation with lower onset overpotential and better catalytic performance, while complex 2 containing a secondary amine fragment displays much lower catalytic activity under identical conditions. The water oxidation catalytic mechanism of the two complexes is proposed based on the electrochemical test results. Experimental methods indicate that phosphate coordinated on the Cu center of the two complexes inhibits their reaction with substrate water molecules, resulting in lower activity toward water oxidation. Electrochemical tests reveal that the structure of the coordinated nitrogen atom improves the catalytic performance of the Cu complexes by modulating the coordination of phosphate on the Cu center, indicating that a minor alteration of the coordinating nitrogen atom of the ligand has a detrimental effect on the catalytic performance of electrochemical WOCs based on transition metal complexes.

Mononuclear ruthenium (II) complex covalently anchored on melem and g-C3N4 as efficient heterogeneous catalysts for chemical water oxidation.

Ru-melem and Ru-C3N4 were synthesized by a simple and facile strategy to construct a novel covalently anchoring by introducing easily synthesized amide bond as a bridge connecting the Ru-terpy and melem or g-C3N4, respectively. The covalent anchoring of Ru complex on melem or C3N4 not only makes these materials exhibit water oxidation activity under CeIV-driven (CeIV = Ce(NH4)2(NO3)6) reaction condition, but also makes the obtained heterogeneous catalysts show higher catalytic activity than the corresponding homogeneous catalysts, which reveals that the covalent anchoring strategy of Ru complex is beneficial to improve the catalytic activity of homogeneous Ru catalysts. The synthetic method of hybrid catalysts offers an insightful strategy for enhancing water oxidation activity of molecular catalysts.

Modulating the electrocatalytic activity of mononuclear nickel complexes toward water oxidation by tertiary amine group.

Water oxidation is the bottleneck of water splitting, which is a promising strategy for hydrogen production. Therefore, it is significant to develop efficient water oxidation catalysts. Herein, electrochemical water oxidation catalyzed by three nickel complexes, namely [Ni(bptn)(H2O)](ClO4)2 (1), [Ni(mbptn)(CH3CN)](ClO4)2 (2), and [Ni(tmbptn)(H2O)](ClO4)2 (3) (bptn = 1,9-bis(2-pyridyl)-2,5,8-triazanonane, mbptn = 5-methyl-1,9-bis(2-pyridyl)-2,5,8-triazanonane, and tmbptn = 1,9-bis(2-pyridyl)-2,5,8-triazanonane), is studied under near-neutral condition (pH 9.0). Meanwhile, the homogeneous catalytic behaviors of the three mononuclear nickel complexes were investigated and confirmed by scanning electron microscopy, energy dispersive spectrometry, X-ray photoelectron spectroscopy and electrochemical method. Complex 1 stabilized by a pentadentate ligand with three N-H fragments homogeneously catalyzes water oxidation to oxygen with the lowest onset overpotential. Complex 2 stabilized by a similar ligand with two N-H groups and one N-CH3 group exhibits relatively higher onset overpotential but higher catalytic current and turnover frequency. However, complex 3 with three N-CH3 coordination environment shows the highest onset overpotential and the highest catalytic current at higher potential. Comparison of catalytic behaviors and ligand structure of the three complexes reveals that the methyl group on the polypyridine amine ligand affects the water oxidation activity of the complexes obviously. The electronic effect of N-CH3 coordination environment leads to higher redox potential of the metal center and potential demand for water oxidation, while it leads to higher reaction activity of high-valent intermediates, which account for higher catalytic current and efficiency of water oxidation. This work reveals that electrocatalytic water oxidation performance of nickel complexes can be finely modulated by constructing suitable N-CH3 coordination.

Immobilization of Metal-Organic Framework MIL-100(Fe) on the Surface of BiVO4: A New Platform for Enhanced Visible-Light-Driven Water Oxidation.

The development of new dual functional photocatalysts is highly desirable for conversion and storage of solar energy. Herein, we first constructed hierarchical structure MIL-100(Fe)@BiVO4 in situ growing MIL-100(Fe) nanoparticles (NPs) on the surface of decahedron BiVO4 under mild hydrothermal conditions. The as-synthesized hybrid nanostructure is unambiguously determined using a series of characterization methods. These results demonstrate that the ultra-tiny MOF MIL-100(Fe) particles are immobilized on the surface of decahedron BiVO4 and the composite exhibits a strong interaction between BiVO4 and MIL-100(Fe). This hybrid material MIL-100(Fe)@BiVO4 is employed as a photocatalyst for water oxidation reaction and demonstrates higher O2 production activity in comparison with bare BiVO4. The best performance obtained at the optimal mass percentage of MIL-100(Fe) (8.0 wt %) reaches 333.3 µmol h-1 g-1 of the O2 evolution rate irradiated with visible light, which is almost 4.3 times higher than bare BiVO4 (77.3 µmol h-1 g-1). The enhanced water oxidation performance is due to the more efficient interfacial electron-hole transfer between MIL-100(Fe) and BiVO4, which is verified by the results of various photo-electrochemical characterizations. Moreover, the as-prepared composite MIL-100(Fe)@BiVO4 also displays excellent stability for visible-light-driven water oxidation. This study affords a rational strategy for the controllable construction by loading metal-organic frameworks on a semiconductor surface, which is a good reference for other artificial photosystems.

Synthesis of a 6-nm-Long Transition-Metal-Rare-Earth-Containing Polyoxometalate.

An extremely long ribbon-shaped polyoxometalate (POM) octamer, {Eu16Co7Se16W128O448(CIT)10(HCIT)2(NO3)4(OH)4(H2O)52} (H4CIT = citric acid), with a maximum length of ca. 6 nm has been obtained, which is the longest molecular POM reported to date and the first Dawson-based 3d-4f-containing selenotungstate(IV). The nanoscale octamer is built from 8 new Dawson-type Eu2W2-substituted selenotungstates {(Eu2W2O4)Se2W14O52} bridged by 12 H4CIT ligands and 3 Co2+ ions, giving rise to a rare giant inorganic-organic hybrid molecular POM with more than 150 metal centers (7 CoII, 16 EuIII, 16 SeIV, and 128 WVI). Especially, with 128 W centers and more than 800 non-H atoms, the POM octamer also represents the largest known 3d-4f-containing polyoxotungstate.

FeO x Derived from an Iron-Containing Polyoxometalate Boosting the Photocatalytic Water Oxidation Activity of Ti3+-Doped TiO2.

The development of efficient and stable catalyst systems using low-cost, abundant, and nontoxic materials is the primary demand for photocatalytic water oxidation. Distinguishing the true active species in a heterogeneous catalytic system is important for construction of efficient catalytic systems. Herein, hydrothermally synthesized Ti3+ self-doped TiO2, labeled as Ti3+/TiO2, was first used as a light absorber in a powder visible light-driven photocatalytic water oxidation reaction. When an iron-containing polyoxometalate Na27[Fe11(H2O)14(OH)2(W3O10)2(α-SbW9O33)6] (Fe11) was used as a cocatalyst, an amorphous layer of active species was wrapped outside the initial Ti3+/TiO2 nanorod and the in situ formed composite was labeled as F/Ti3+/TiO2. When the composite F/Ti3+/TiO2 was tested as a photocatalytic water oxidation catalyst, dramatically improved oxygen evolution performance was achieved. The composite F/Ti3+/TiO2 showed an oxygen evolution rate of 410 µmol/g/h, which was about 11-fold higher than that of prism Ti3+/TiO2. After 24 h of illumination, an O2 yield of 36.4% was achieved. The contrast experiments, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy characterization demonstrated that FeO x is the true cocatalyst that enhanced the oxygen evolution activity of TiO2. A recycling experiment proved that the composite F/Ti3+/TiO2 has favorable stability in the oxygen production process.

Enhanced photocatalytic activity of BiVO4 coupled with iron-based complexes for water oxidation under visible light irradiation.

[Fe2(TPA)2(µ-O)Cl2]2+ (TPA = tris(2-pyridylmethyl)amine) was investigated as a pre-catalyst, and greatly enhanced the photocatalytic water oxidation activity of BiVO4. An extremely high oxygen yield of 99.1% and apparent quantum yield of 44.3% were obtained in the BiVO4-NaIO3 photocatalytic water oxidation system.

An octanuclear Cu(ii) cluster with a bio-inspired Cu4O4 cubic fragment for efficient photocatalytic water oxidation.

An octanuclear Cu(ii) cluster [Cu8(dpk·OH)8(OAc)4](ClO4)4 (dpk·OH = the monoanion of the hydrated, gem-diol form of di-2-pyridyl ketone) that contains two Cu4O4 cubic fragments similar to the Mn4CaO5 cluster in photosystem II (PSII) was found to be an efficient catalyst for photocatalytic water oxidation. In the [Ru(bpy)3]2+/Na2S2O8 system, it afforded an optimal oxygen yield, turnover number (TON) and turnover frequency (TOF) of 35.6%, 178 and 3.6 s-1, respectively, which are the highest values amongst all of the Cu-based photocatalytic water oxidation catalysts (WOCs).

Renal protective effects of pitavastatin on spontaneously hypercholesterolaemic Imai Rats.

BACKGROUND: Independent of their lipid-lowering effects, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have renal protective effects on various models of progressive renal diseases, therefore, additional therapeutic advantages have been considered. In the present study, using spontaneously hypercholesterolaemic Imai rats, we examined the protective effects of pitavastatin on renal injuries and the oxidative modification of the low-density lipoprotein (LDL) and high-density lipoprotein (HDL), since oxidized lipoproteins are speculated to be involved in the mechanism of this rat strain's renal injuries. METHODS: Male Imai rats were treated with pitavastatin (n = 11) at a dose of 100 mg/kg diet or received no specific therapy as controls (n = 11) from 10 to 22 weeks of age. Body weight, urinary protein excretion and serum constituents were evaluated every 4 weeks. At the end of the study, the effects of pitavastatin on the susceptibility of serum LDL and HDL to oxidation, and renal histology were examined. RESULTS: Pitavastatin treatment did not affect hyperlipidaemia, but significantly reduced proteinuria and preserved creatinine clearance deterioration. At the end of the study, lag times for LDL and HDL oxidation were prolonged by the treatment of pitavastatin to 126 and 153%, respectively, compared with the controlled group. The glomerulosclerosis index (SI) for untreated controlled rats was significantly higher than that for the pitavastatin-treated group. An immunohistochemistry study showed significantly lower numbers of ED-1 positive macrophages in the glomeruli and interstitium in pitavastatin-treated rats compared with those controlled. CONCLUSION: Pitavastatin treatment prevented renal injuries in Imai rats independent of lipid-lowering effects. Prevention of oxidative modification of LDL and HDL may play an important role on the beneficial effects of pitavastatin treatment.

Various dietary protein intakes and progression of renal failure in spontaneously hypercholesterolemic Imai rats.

BACKGROUND/AIM: Dietary protein restriction is known to be beneficial in the preservation of the renal function in patients with chronic renal failure. Recently, the effect of varying quantity and quality of dietary protein intakes was also studied. This study investigates the effects of different dietary animal proteins on renal function in spontaneously hypercholesterolemic Imai rats that exhibit renal lesions similar to human focal and segmental glomerulosclerosis. The sources of proteins were from casein, pork, and fish. Primary concern was the effect of fish meat protein, because the effects of fish oil are well reported. To examine whether remnants of fish oil affect the experimental results, semi-defatted fish meat and fully defatted fish meat were prepared for these experiments. METHODS: Forty-two Imai rats were placed on diets containing casein, defatted pork meat, semi-defatted fish meat, or defatted fish meat as a protein sources from 10 to 22 weeks of age. Twenty-four hour urine collections were obtained along with measurements of systolic blood pressure and drawing blood from the tail artery every 4 weeks. Finally, the kidneys were removed and prepared for histological study. RESULTS: The semi-defatted fish meat diet retarded the rise of plasma cholesterol, virtually completely prevented the development of hypertriglyceridemia, and slowed the progression of proteinuria, renal function failure, and glomerular injury as compared with the control casein diet. However, the fully defatted fish meat diet led to renal failure at the same rate as the casein diet. The defatted pork diet group exhibited a higher creatinine clearance at the end of the experiments as compared with the casein and the fully defatted fish meat diet groups. CONCLUSIONS: These data suggest that an important determinant of the protective effects of the semi-defatted fish meat diet was related to the prevention of hypercholesterolemia and hypertriglyceridemia by the remaining fish oil. Fish meat protein itself did not indicate superior beneficial effects in the regression of the renal function in Imai rats as compared with casein protein, and defatted pork showed better results than casein and fully defatted fish meat.

The efficacy of vitamin E against oxidative damage and autoantibody production in systemic lupus erythematosus: a preliminary study.

The hypothesis that reactive oxygen species (ROS) modification of DNA is involved in the development of autoantibodies in systemic lupus erythematosus (SLE) is supported by the enhanced reactivity of anti-DNA antibodies to ROS-denatured DNA. We studied the efficacy of vitamin E against both oxidative DNA damage and autoantibody production in SLE. Urinary 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative DNA damage, and the anti-double-stranded DNA (anti-ds DNA) antibody, a predictor of disease activity, were assayed twice, first during the season with the most intense sunlight and then later in the year. Twelve women among 36 outpatients received vitamin E (150 to 300 mg/day) together with prednisolone (PSL). No significant age or daily dose of PSL differences were evident between patient groups. Urinary 8-OHdG in the PSL with vitamin E group (15.0 +/- 10.2 ng/mg during the period of intense sunlight and 11.7 +/- 8.7 ng/mg during the remainder of the year) did not differ significantly from that in the PSL without vitamin E group (20.0 +/- 23.2 and 11.0 +/- 5.9 ng/mg, at these respective times), but the anti-ds DNA antibody titer in the PSL with vitamin E group (17.9 +/- 20.3 IU/l during the period of intense sunlight and 16.3 +/- 19.4 IU/l during the remainder of the year) was significantly lower than that in the PSL without vitamin E group for both sunlight-defined periods (66.3 +/- 76.8 and 55.8 +/- 59.0 IU/l, at these respective times; P < 0.05). The present study suggests that vitamin E can suppress autoantibody production via a mechanism independent of antioxidant activity.

[Fish meat retarding the progression of chronic renal failure in spontaneously hypercholesterolemic rats].

OBJECTIVE: To investigate the effects of different dietary proteins of fish meat and casein upon the progression of chronic renal failure (CRF) in spontaneously hypercholesterolemic (SHC) rats. METHODS: 48 SHC rats of 10 weeks of age were randomly divided into four groups, and placed on diets containing 20% and 40% casein or fish protein respectively till they were 22 weeks of age. 24-hour urine collections were obtained along with measurements of systolic blood pressure and blood were drew from their tail vein evry 4 weeks. Finally, the kidneys were removed and prepared for histological and immunohistochemistry study . RESULTS: Fish meat diet slowed the progression of proteinuria, renal function failure and glomerular injury compared with the control casein diet in both 20% and 40% dietary groups. CONCLUSION: Fish meat retarded the progression of CRF in SHC rats compared with casein.

STAT6 deficiency inhibits tubulointerstitial fibrosis in obstructive nephropathy.

To elucidate the contribution of signal transducer and activator of transcription (STAT) 6 to the pathophysiology of chronic renal injury, STAT6-/- mice were subjected to unilateral ureteral ligation together with wild-type control mice. STAT6-/- kidneys had more apoptotic cells and a greater influx of F4/80-positive cells than wild-type kidneys following ureteral obstruction. There was a much larger alpha-smooth muscle actin-positive area in STAT6-/- kidneys than in wild-type kidneys after ureteral ligation. However, renal fibrosis, as quantified by Masson-Trichrome staining, was not significantly exaggerated in STAT6-/- kidneys compared with wild-type kidneys. The accumulation of collagen I was significantly less in STAT6-/- kidneys than in wild-type kidneys. These observations indicate that the STAT6 signal transduction pathway exerts a protective role on renal cell apoptosis in chronic obstructive uropathy. Our findings also suggest that the STAT6 pathway may have a promotive effect on renal fibrosis by activating collagen synthesis following ureteral obstruction.

[Atherosclerosis and vascular calcification in hemodialysis patients].

Cardiovascular disease is the largest cause of mortality in hemodialysis patients. Cardiovascular mortality is fivefold to twentyfold higher in hemodialysis patients than in the general population. Atherosclerosis and vascular calcification are the characteristic complications in hemodialysis patients. Hemodialysis patients have traditional risk factors such as abnormal lipid metabolism and uremia-related risk factors such as oxidative stress and hyperphosphatemia. Oxidative stress takes place by increased production of oxidants by leukocytes and antioxidant loss of vitamin C and E. Oxidatively modified LDL exist in the circulation by excess of oxidative stress in hemodialysis patients. Oxidative stress is a major contributor to accelerated development atherosclerosis. Oxidative stress and hyperphosphatemia also influence vascular calcification. The pattern of vascular calcification in hemodialysis patient is characterized by mineral deposition in the tunica media. It is reported that the obvious calcification in aorta and artery of the MGP knockout mouse is recognized. It is indicated that MGP has the inhibitory effect of the calcification of vessel wall. Vitamin E protects atherosclerosis and vascular calcification in hemodialysis patients. It is also important to control hyperphosphatemia for vascular calcification.

Hypotensive effects of neuromedin U microinjected into the cardiovascular-related region of the rat nucleus tractus solitarius.

Neuromedin U (NMU) is a brain-gut peptide with potent contractile effects on the uterus and smooth muscle. Intracerebroventricular injection of NMU reportedly decreased food intake and body-weight gain in the rat. We evaluated the effects of NMU delivered by microinjection into the rat nucleus tractus solitarius (NTS) on cardiovascular responses. At the concentrations used (5, 10 or 50 pmol), the intra-NTS injection of NMU in artificial cerebrospinal fluid produced a significant reduction in both the mean arterial pressure and heart rate. The hypotensive responses were dose dependent. Our findings suggest that NMU may act as a neurotransmitter or neuromodulative substance that causes excitation of neurons in the NTS and that it may play a role in cardiovascular regulation in vivo.

[Interstitial nephritis induced by mesalazine].

This report concerns the first case in Japan of interstitial nephritis induced by mesalazine, a new therapeutic agent for inflammatory bowel disease, such as ulcerative colitis. Twenty-two cases have already been reported in other countries. The patient, a 27-year-old woman, was treated with mesalazine for her ulcerative colitis at another hospital. At the beginning of her treatment, her serum creatinine level was within the normal range. After 12 months, this level increased up to 5.7 mg/dl. She was then referred to our hospital for renal investigation and therapy. A renal biopsy revealed that severe tubulo-interstitial nephritis had occurred. Her mesalazine treatment was withdrawn and prednisolone was administered. Her serum creatinine level decreased gradually. However, this level remained at about 2.8 mg/dl and stabilized at that level. She was then discharged from the hospital. Glomeruli appeared to have minor glomerular abnormalities except for one globally sclerosed glomerulus as observed by light microscopy. However, IgM and C3 deposition on glomeruli were also observed. Glomerular lesions were suspected from these histological findings. A similar case that showed IgM. C3 depositions in glomeruli has previously been reported. The possibility of glomerular lesions being induced by mesalazine should be further researched. From the summary of reported cases, a delay of diagnosis of interstitial nephritis induced by mesalazine has resulted in permanent irreversible renal failure. Intensive monitoring of renal function is required when a patient is treated with mesalazine.

Effect of environmental changes on oxidative deoxyribonucleic acid (DNA) damage in systemic lupus erythematosus.

In a study conducted in Japan, the authors used urinary 8-hydroxydeoxyguanosine (8-OHdG) to study the effects of high-intensity and low-intensity sunlight on oxidative damage to deoxyribonucleic acid (DNA) in patients who had systemic lupus erythematosus (SLE). During late May through early September (i.e., a period of high-intensity sunlight), the mean urinary 8-OHdG level in SLE patients was significantly higher than in controls (31.0 +/- 20.6 [standard deviation] ng/mg vs. 15.4 +/- 7.2 ng/mg, respectively [p < .05]). During late November through early March (i.e., low-intensity sunlight season), however, no significant differences were noted (15.4 +/- 5.5 ng/mg vs. 16.3 +/- 4.6 ng/mg, respectively). The mean urinary 8-OHdG level in SLE patients during the period of high-intensity sunlight was significantly higher than during the period of low-intensity sunlight (21.3 +/- 20.6 ng/mg vs. 12.6 +/- 6.7 ng/mg, respectively; p < .01), although no such seasonal changes were observed among controls (16.2 +/- 8.0 ng/mg vs. 15.7 +/- 5.1 ng/mg, respectively). The effect of sunlight intensity (i.e., season) may require consideration when oxidative DNA damage occurs in individuals who have SLE.