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ABSTRACT: Syntheses of five types of tungsten-iron-sulfur/selenium clusters, namely, incomplete cubanes, single cubanes, edge-bridged double cubanes (EBDCs), P(N)-type clusters, and double-cuboidal clusters, have been devised using the concept of template-assisted assembly. The template reactant is six-coordinate [(Tp*)W(VI)S(3)](1-) [Tp* = tris(3,5-dimethylpyrazolyl)hydroborate(1-)], which in the assembly systems organizes Fe(2+/3+) and sulfide/selenide into cuboidal [(Tp*)WFe(2)S(3)] or cubane [(Tp*)WFe(3)S(3)Q] (Q = S, Se) units. With appropriate terminal iron ligation, these units are capable of independent existence or may be transformed into higher-nuclearity species. Selenide is used as a surrogate for sulfide in cluster assembly in order to determine by X-ray structures the position occupied by an external chalcogenide nucleophile or an internal chalcogenide atom in the product clusters. Specific incorporation of selenide is demonstrated by the formation of [WFe(3)S(3)Se](2+/3+) cubane cores. Reductive dimerization of the cubane leads to the EBDC core [W(2)Fe(6)S(6)Se(2)](2+) containing μ(4)-Se sites. Reaction of these species with HSe(-) affords the P(N)-type cores [W(2)Fe(6)S(6)Se(3)](1+), in which selenide occupies μ(6)-Se and μ(2)-Se sites. The reaction of [(Tp*)WS(3)](1-), FeCl(2), and Na(2)Se yields the double-cuboidal [W(2)Fe(4)S(6)Se(3)](2+/0) core with μ(2)-Se and μ(4)-Se bridges. It is highly probable that in analogous sulfide-only assembly systems, external and internal sulfide reactants occupy corresponding positions in the cluster products. The results further demonstrate the viability of template-assisted cluster synthesis inasmuch as the reduced (Tp*)WS(3) unit is present in all of the clusters. Structures, zero-field Mössbauer data, and redox potentials are presented for each cluster type.
Journal of the American Chemical Society 03/2012; 134(14):6479-90. · 9.91 Impact Factor
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Cell biochemistry and biophysics 03/2012; 62(2):407. · 3.34 Impact Factor
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ABSTRACT: Increased levels of homocysteine are found systemically and in intestinal mucosa of patients with inflammatory bowel disease, and, specifically, in ulcerative colitis (UC). However, there are controversial reports regarding the factors contributing to increased levels of homocysteine in UC. Furthermore, little information is available regarding the relationship between hyperhomocysteinemia (HHcy), vitamin status, and genetic polymorphisms of homocysteine-related enzymes in these patients. This study examined four functional polymorphisms linked to homocysteine metabolism (MTHFR C677T and A1298C, MTR A2756G and MTRR A66G), and evaluated plasma levels of homocysteine, folate, and vitamin B(12) in 310 consecutive patients with UC and 936 age- and sex-matched healthy controls from southeast China. The variant allele and genotypic frequencies in MTHFR A1298C, MTR A2756G and MTRR A66G genes were significantly higher in patients with UC compared to healthy controls. Further, HHcy and low levels of folate and vitamin B(12) were more frequent in patients with UC. The MTR 2756G allele, extent of the disease, and gender were the independent determinants of HHcy in these patients. These findings suggest that genetic and nutritional factors have a synergetic effect on HHcy in patients with UC. In conclusion, our data highlight a prevention strategy for moderation of HHcy and supplementation with folate and vitamine B(12) in patients with UC from Southeast China.
Cell biochemistry and biophysics 09/2011; 62(1):203-10. · 3.34 Impact Factor
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ABSTRACT: To investigate the association between the genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) and ulcerative colitis (UC) of Han ethnic population in Zhejiang, China.
Two hundred and seventy-four consecutive patients with UC and 726 healthy controls (HC) were studied. The genetic polymorphisms of MTHFR (C677T and A1298C) were genotyped using PCR-RELP methods.
The frequencies of variant allele and genotype in MTHFR A1298C gene were higher in UC patients than in the HC (35.77% vs 29.96%, P = 0.013; 52.19% vs 44.90%, P = 0.039; respectively). However, there were no significant discrepancies of the allele and genotype frequencies in the MTHFR C677T gene between the UC patients and the HC (P > 0.05). In addition, the MTHFR 677TT homozygote, T allele and 677CT/1298AC compound genotype were more prevalent in patients with extensive colitis than in those with distal colitis (37.66% vs 14.72%, P = 0.0002; 49.35% vs 32.99%, P = 0.0004; 29.87% vs 15.23%, P = 0.006; respectively). Furthermore, the variant allele in the MTHFR A1298C gene (C) in severe UC patients was significantly lower than in mild and moderate UC patients (18.97% vs 33.88%, P = 0.022).
The genetic polymorphisms of MTHFR C677T and A1298C are obviously associated with Han ethnic population with UC in Zhejiang province.
Zhonghua nei ke za zhi [Chinese journal of internal medicine] 05/2011; 50(5):374-7.
