Metal Phosphate-Supported Pt Catalysts for CO Oxidation

Oxides (such as SiO₂, TiO₂, ZrO₂, Al₂O₃, Fe₂O₃, CeO₂) have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, denoted as Ca-P-O here) also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La) catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N₂ adsorption-desorption, inductively coupled plasma (ICP) atomic emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO₂ temperature-programmed desorption (CO₂-TPD), X-ray photoelectron spectroscopy (XPS), and H₂ temperature-programmed reduction (H₂-TPR). This work furnishes a new catalyst system for CO oxidation and other possible reactions.     

Isolation and characterisation of mineral-oxidising “Acidibacillus” spp. from mine sites and geothermal environments in different global locations

Eight strains of acidophilic bacteria, isolated from mine-impacted and geothermal sites from different parts of the world, were shown to form a distinct clade (proposed genus “Acidibacillus”) within the phylum Firmicutes, well separated from the acidophilic genera Sulfobacillus and Alicyclobacillus. Two of the strains (both isolated from sites in Yellowstone National Park, USA) were moderate thermophiles that oxidised both ferrous iron and elemental sulphur, while the other six were mesophiles that also oxidised ferrous iron, but not sulphur. All eight isolates reduced ferric iron to varying degrees. The two groups shared <95% similarity of their 16S rRNA genes and were therefore considered to be distinct species: “Acidibacillus sulfuroxidans” (moderately thermophilic isolates) and “Acidibacillus ferrooxidans” (mesophilic isolates). Both species were obligate heterotrophs; none of the eight strains grew in the absence of organic carbon. “Acidibacillus” spp. were generally highly tolerant of elevated concentrations of cationic transition metals, though “A. sulfuroxidans” strains were more sensitive to some (e.g. nickel and zinc) than those of “A. ferrooxidans”. Initial annotation of the genomes of two strains of “A. ferrooxidans” revealed the presence of genes (cbbL) involved in the RuBisCO pathway for CO₂ assimilation and iron oxidation (rus), though with relatively low sequence identities.     

Human apolipoprotein A-I Gly26Arg stimulation of inflammatory responses via NF-kB activation: Potential roles in amyloidosis?

The cascade of molecular events leading to Human apolipoprotein A–I (apoA–I) amyloidosis is not completely understood, not even the pathways that determine clinical manifestations associated to systemic protein deposition in organs such as liver, kidney and heart. About twenty natural variants of apoA–I were described as inducing amyloidosis, but the mechanisms driving their aggregation and deposition are still unclear. We previously identified that the mutant Gly26Arg but not Lys107-0 induced the release of cytokines and reactive oxygen species from cultured RAW 264.7 murine macrophages, suggesting that part of the pathogenic pathway could elicit of an inflammatory signal. In this work we gained deep insight into this mechanism and determined that Gly26Arg induced a specific pro-inflammatory cascade involving activation of NF-κB and its translocation into the nucleus. These findings suggest that some but not all apoA–I natural variants might promote a pro-oxidant microenvironment which could in turn result in oxidative processing of the variants into a misfolded conformation.     

甲醛对人Ⅱ型肺泡上皮细胞DNA氧化和甲基化水平的影响

目的：分析甲醛染毒对体外培养的人Ⅱ型肺泡上皮细胞(A549)内8-羟基鸟嘌呤脱氧核苷(8-oxo-dG)水平、DNA5-甲基胞嘧啶(5-mC)含量的影响及其时间-效应和剂量-效应关系，探讨甲醛所致的细胞DNA氧化与DNA甲基化的关联性。方法：用5～20μmol/L甲醛作用于A549细胞，用高压液相色谱串联电化学检测技术分析细胞DNA8-oxo-dG水平，用免疫荧光和高效毛细管电泳法检测细胞全基因组DNA5-mC含量改变。 结果：甲醛染毒提高了细胞8-oxo-dG水平，但是降低了细胞的DNA5-mC含量。甲醛致细胞DNA氧化与DNA甲基化呈现不同特点，A549细胞暴露于20 μmol/L 甲醛后，DNA氧化水平在1周甚至更早时间就已显著增高，而相同条件下DNA 甲基化水平的改变需要6周以上的时间，DNA 甲基化的改变滞后于DNA氧化。 A549细胞经5～20μmol/L甲醛染毒8周后，DNA氧化水平与甲醛剂量呈正相关关系，而同样条件下DNA甲基化水平与甲醛剂量呈负相关关系。 结论：甲醛染毒可提高DNA氧化水平，降低细胞DNA甲基化水平。在甲醛的毒作用效应中，细胞DNA氧化损伤可能是早于其DNA甲基化的一个重要分子事件。     

Marmoset cytochrome P450 2B6, a propofol hydroxylase expressed in liver

1. The common marmoset (Callithrix jacchus) is a useful experimental animal to evaluate the pharmacokinetics of drug candidates. Cytochrome P450 (P450) 2B enzyme in marmoset livers has been identified; however, only limited information on the enzymatic properties and distribution has been available.

2. Marmoset P450 2B6 amino acids showed high sequence identities (>86%) with those of primates including humans and cynomolgus monkeys. Phylogenetic analysis using amino acid sequences indicated that marmoset P450 2B6 was closer to human and cynomolgus monkey P450 2B6 than to P450 2B orthologs of other species, including pigs, dogs, rabbits and rodents.

3. Quantitative polymerase chain reaction analysis using specific primers showed P450 2B6 mRNA predominantly expressed in livers among the five marmoset tissues, similar to those of humans and cynomolgus monkeys.

4. Marmoset P450 2B6 heterologously expressed in Escherichia coli membranes oxidized 7-ethoxycoumarin, pentoxyresorufin, propofol and testosterone, at roughly similar rates to those of humans and/or cynomolgus monkeys. A high capacity of marmoset P450 2B6 with propofol 4-hydroxylation (at low ionic strength conditions) with a low K_m value was relatively comparable to that for marmoset livers.

5. These results collectively indicated a high propofol 4-hydroxylation activity of P450 2B6 expressed in marmoset livers.

     

Peroxynitrite modified DNA may be an antigenic trigger for antibodies in various cancers of gynecologic origin

This study aimed towards probing the role of peroxynitrite damaged human DNA (ONOO^–-DNA) in the induction of circulating antibodies in certain cancers of gynecologic origin. We have compared the binding specificity of DNA isolated from the lymphocytes of cancer patients with that of the experimentally modified DNA. Also, the induced anti-ONOO⁻-DNA antibodies have been used to probe oxidative damage in the DNA isolated from cancer patients. Human placental DNA was modified with peroxynitrite (ONOO⁻) and analyzed by ultraviolet (UV) and fluorescence spectroscopy, gel electrophoresis, thermal denaturation profile, etc. Antibodies against modified DNA were induced in experimental animals. Specific binding of the antibodies was evaluated by ELISA and band shift assay. 91 cancer patients were selected and grouped according to the type of cancer. Specific binding characteristics of circulating autoantibodies (IgG) were determined by competitive-inhibition ELISA, using different inhibitors. Maximum inhibition of antibody activity by ONOO⁻-DNA reflected specific recognition of modified epitopes by cancer IgG. This shows generation of neo-epitopes on DNA, upon modification with ONOO⁻, that are recognized by cancer IgG. Our results indicate epitope sharing between the DNA isolated from cancer patients and the in-vitro modified ONOO⁻-DNA. The possible role of nitrosative stress in the gynecologic oncology has been discussed.     

Dietary fiber and flavan-3-ols in shortbread biscuits enriched with barley flours co-products

The coarse fraction obtained by air classification of barley flour, rich in dietary fiber and flavan-3-ols, was utilized to develop functional biscuits. The flavan-3-ol content, antioxidant activity and oxidative stability of biscuits were measured during storage under retail conditions for 1 year. The replacement of 60% (w/w) refined wheat flour with barley coarse fraction increased the ash, fiber and flavan-3-ol contents significantly. Biscuit samples enriched with barley coarse fraction had a significantly higher amount of fiber compared with the control sample (six times higher). The β-glucan content in enriched samples was 15 times higher than control samples. The flavan-3-ol loss in biscuits after baking was about 67%. The initial content of flavan-3-ols increased from 0.6 to 4.3 mg/100 g in biscuits formulated with barley coarse fraction and showed improved antioxidant properties. Lipid oxidation increased during the shelf-life; the enriched biscuit showed the higher lipid oxidation status, but the level reached during the shelf-life was lower than the limit of acceptance reported for bakery products and, for this reason, does not compromise the safety.     

Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C–H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C–H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes.