利用甲烷氧化菌Methylosinus trichosporium OB3b生产四氢嘧啶的研究

在盐浓度为0.03%(最适生长盐浓度)条件下培养甲基弯菌Methylosinus trichosporium OB3b,选用有机溶剂法提取胞内与胞外的四氢嘧啶,选用紫外-可见光谱、薄层色谱、红外色谱定性分析和高效液相色谱进行定量检测。结果表明,甲基弯菌OB3b在最适盐浓度下可以合成并分泌四氢嘧啶,平均产量为(84.9±5.49) mg/(g·d),最大产量为139.75 mg/(g·d)。该产量略高于目前国际上经常报道的甲烷氧化菌Methylomicrobium alcaliphilum20Z合成四氢嘧啶的产量。虽然甲烷氧化菌合成四氢嘧啶的产量低于目前工业所使用菌株,但其可用以甲烷为唯一碳源的无机盐液体培养基培养,在较低盐条件下合成四氢嘧啶,分离纯化容易,经济价值高。     

Methylosinus trichosporium OB3b整细胞催化丙烯制备环氧丙烷的工艺条件

甲烷氧化菌的甲烷单加氧酶（MMO）可以在常温常压下直接一步氧化丙烯生成环氧丙烷,而且除了产物外只有水产生,和目前化学工业所使用的方法相比具有条件温和、选择性高等特点。在优化了甲烷氧化菌Methylosinus. trichosporium OB3b整细胞催化丙烯生产环氧丙烷的各个参数的基础上,选用本实验室建立起来的高密度培养甲烷氧化菌的方法来培养细胞,并研究该细胞催化丙烯生成环氧丙烷的工艺特性,结果可使环氧丙烷的积累浓度达到了目前文献已报道最高浓度的约4倍。     

The effect of amino acids and amino acid analogues on growth of an obligate methanotroph,Methylosinus trichosporium OB3b

The sensitivity of the obligate methanotroph, Methylosinus trichosporium OB3b to a number of amino acid analogues and amino acids has been examined. Sulphaguanidine (5 μg ml^?1) norleucine (100 μg ml^?1) m-fluorophenylalanine (50 μg ml^?1), p-fluorophenylalanine (50 μg ml^?1) and S2-aminoethyl-C-cysteine (1000 μg ml^?1) inhibited growth. Proline, threonine, methionine and lysine (2–4 μg ml^?1) also inhibited growth, but arginine and leucine at similar concentrations had no effect. Attempts were made to isolate amino acid analogue resistant mutants, which would be expected to overproduce amino acids. Two approaches were made, selection of spontaneous and induced mutants in plate culture, and selection of a spontaneous mutant during growth in continuous culture under selective conditions, but no mutants were obtained. Possible reasons for failure to obtain such mutants are discussed.     

苯酚双氧水羟基化反应催化剂研究进展

综述了双氧水氧化苯酚制备苯二酚所用催化剂研究的近期进展。目前研制开发的新颖、性能优良的催化剂有：杂原子分子筛,复合金属氧化物及其负载型催化剂和金属络合物及其负载型催化剂等３种。讨论了它们的制备、性能和应用前景。     

不同催化剂在过氧化氢氧化苯酚反应中的催化效果

主要对过氧化氢氧化苯酚反应中Fe2 + 的催化特性进行了实验研究 ,结果得出 :当Fe2 + 浓度为 0～0 0 5mmol·L-1时 ,催化活性增长显著 ,当浓度为 0 0 5～ 0 2 5mmol·L-1时 ,催化活性呈缓慢增长趋势 ,等量铁离子 (Fe3 + +Fe2 + )中不同含量的Fe3 + 对反应无明显影响。通过对相同实验条件下不同催化剂 (Fe2 + ,Cu2 + ,Fe2 + -Co2 + ,Fe2 + -Ce4+ ,Co -Fe -oxide)催化效果的研究发现 ,Fe2 + 作催化剂时苯酚与过氧化氢的转化率最高 ,Cu2 + 和Ce4+ 有利于邻 /对苯二酚含量比的提高     

Structures of the Apo and FAD‐Bound Forms of 2‐Hydroxybiphenyl 3‐monooxygenase (HbpA) Locate Activity Hotspots Identified by Using Directed Evolution

The FAD‐dependent monooxygenase HbpA from Pseudomonas azelaica HBP1 catalyses the hydroxylation of 2‐hydroxybiphenyl (2HBP) to 2,3‐dihydroxybiphenyl (23DHBP). HbpA has been used extensively as a model for studying flavoprotein hydroxylases under process conditions, and has also been subjected to directed‐evolution experiments that altered its catalytic properties. The structure of HbpA has been determined in its apo and FAD‐complex forms to resolutions of 2.76 and 2.03 Å, respectively. Comparisons of the HbpA structure with those of homologues, in conjunction with a model of the reaction product in the active site, reveal His48 as the most likely acid/base residue to be involved in the hydroxylation mechanism. Mutation of His48 to Ala resulted in an inactive enzyme. The structures of HbpA also provide evidence that mutants achieved by directed evolution that altered activity are comparatively remote from the substrate‐binding site.     

11α hydroxylation of 16α, 17‐epoxyprogesterone in biphasic ionic liquid/water system by Aspergillus ochraceus

BACKGROUND: The improved efficiency of steroid biotransformation using the biphasic system is generally attributed to the positive effect on the solubility of substrate in aqueous media. A promising alternative for the application of organic solvents in biphasic systems is the use of ionic liquids (ILs). This study aims to investigate the applicability of the biphasic ILs/water system for 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by Aspergillus ochraceus. RESULTS: Of the seven ILs tested, [C₃mim][PF₆] exhibited the best biocompatibility, with markedly improved biotransformation efficiency. In the [C₃mim][PF₆]‐based biphasic system, substrate conversion reached 90% under the condition in which buffer pH, volume ratio of buffer to ILs, cell concentration, and substrate concentration were 4.8, 10/1, 165 g L^?1 and 20 g L^?1, respectively. This is more efficient than that of the monophasic aqueous system. The effects of the cations and anions of these ILs on the 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus is also discussed. CONCLUSION: The above results showed that IL/water biphasic system improved the efficiency of 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus, thus suggesting the potential industrial application of ILs‐based biphasic systems for steroid biotransformation. © 2012 Society of Chemical Industry     

Asymmetric α‐Hydroxylation of β‐Indanone Esters and β‐Indanone Amides Catalyzed by C‐2′ Substituted Cinchona Alkaloid Derivatives

The highly catalytic asymmetric α‐hydroxylation of β‐indanone esters and β‐indanone amides using peroxide as the oxidant was realized with a new C‐2′ substituted Cinchona alkaloid derivatives. The two enantiomers of α‐hydroxy‐β‐indanone esters could be obtained by simply changing the oxidant. This protocol allows a convenient access to the corresponding α‐hydroxy‐β‐indanone esters and α‐hydroxy‐β‐indanone amides with up to 99% yield and 98% ee.

     

The formation of para-benzoquinone and the mechanism of the hydroxylation of phenol by hydrogen peroxide over solid acids

The transient formation of para-benzoquinone during the hydroxylation of phenol by hydrogen peroxide over solid acids is investigated. Formed by overoxidation of hydroquinone, para-benzoquinone is involved in an acid catalysed redox process responsible for the autocatalysis of the reaction and for a partial decomposition of hydrogen peroxide into oxygen and water.     

Effect of the hydrogen spillover on the selectivity of dibenzothiophene hydrodesulfurization over CoSx/γ-Al2O3, NiSx/γ-Al2O3 and MoS2/γ-Al2O3 catalysts

Dibenzothiophene (DBT) hydrodesulphurization (HDS) reaction at 3 MPa and 325–375 °C on Mo/γ-Al₂O₃ single-bed and Me/γ-Al₂O₃//SiO₂//Mo/γ-Al₂O₃ (Me = Co or Ni) double-bed catalysts were investigated. Results indicate that ratio cyclohexylbenzene (CHB)/biphenyl (BP) or selectivity is higher when using double-beds rather than a single-bed. Synergy in dibenzothiophene hydrodesulphurization on Co//Mo and Ni//Mo double-beds is also detected. Changes in selectivity and conversion are attributed to the action of spillover hydrogen (Hso) formed in the first bed that reaches the second bed.     

Reduction of aromatic nitro compounds on Pd colloids prepared by γ-irradiation

Poly(vinylpyrrolidone) (PVP), stabilized Pd colloids were successfully prepared by γ-irradiation in aqueous solution without additional reducing agent. The ‘clean’ Pd colloid was used as catalysts for the reduction of 2-, 3-, 4-nitrophenol, 2,4,6-trinitrotoluene, and 4-nitrobenzo-15-crown in aqueous solution at room temperature. The reduction process was monitored by UV–Visible spectroscopy.     

Mechanistic Study of the Reaction of Thiol‐Containing Enzymes with α,β‐Unsaturated Carbonyl Substrates by Computation and Chemoassays

We investigated the reactions between substituted α,β‐unsaturated carbonyl compounds (Michael systems) and thiols by computations as well as chemoassays. The results give insight into variations in the underlying mechanisms as a function of the substitution pattern. This is of interest for the mechanisms of inhibition of the SARS coronavirus main protease (SARS‐CoV M^pro) by etacrynic acid derivatives as well as for the excess toxicity of substituted α,β‐unsaturated carbonyl compounds. This study compares possible reaction courses including 1,4‐addition followed by a ketonization step, and underscores the importance of a base‐catalyzed step for the reactivity of thiol groups in enzymes. Phenyl and methyl substituents at the Michael system decrease the reactivity of the electrophilic compound, but chlorophenyl substituents partly recover the reactivity. Computations also indicate that electron‐pushing substituents lead to a change in the reaction mechanism. The conformation of the Michael system is also found to significantly influence reactivity: the s‐cis conformation leads to higher reactivity than the s‐trans conformation. The computed data explain the trends in measured inhibition potencies of substituted α,β‐unsaturated carbonyl compounds and of reaction rates in chemical assays. They also indicate that the reversibility of inhibition does not stand in contrast to the formation of a new covalent bond between inhibitor and protease.     

The Expression Levels of SARS-CoV-2 Infection-Mediating Molecules Promoted by Interferon-γ and Tumor Necrosis Factor-α Are Downregulated by Hydrogen Sulfide

Autoimmune thyroid diseases (AITDs), which include Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), have a higher prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the literature. The effects of AITD-associated cytokines on SARS-CoV-2 infection-mediating molecule levels might be involved in the pathogenesis of susceptibility. We speculated that hydrogen sulfide (H₂S) might attenuate this process since H₂S has antiviral effects. Using immunohistochemistry, we found that angiotensin-converting enzyme-II (ACE2) expression was higher in the HT group and neuropilin 1 (NRP1) expression was higher in HT and GD groups than in the normal group, while transmembrane protease serine type 2 (TMPRSS2) expression was lower in HT and GD groups. When culturing primary thyrocytes with cytokines or sodium hydrosulfide (NaHS) plus cytokines, we found that ACE2 and NRP1 mRNA levels were upregulated while TMPRSS2 levels were downregulated by interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). After pretreatment with NaHS in thyrocytes, ACE2 and NRP1 expression were downregulated compared to IFN-γ or TNF-α treatment, and NaHS had no effect on TMPRSS2 expression. Our findings suggested that IFN-γ and TNF-α, which are elevated in AITDs, promoted ACE2 and NRP1 expression and inhibited TMPRSS2 expression. H₂S might protect against SARS-CoV-2 infection by downregulating ACE2 and NRP1 levels.     

β‐Cyclodextrin inclusive interaction driven separation of organic compounds

A novel selective separation method for organic compounds, especially thermosensitive substances, has been proposed using unsubstituted β‐cyclodextrin (β‐CD) as a host and some alcohols and aldehydes as model guests in aqueous solution. The separation factors were evaluated from the extraction of an equimolar mixture of alcohol and aldehyde compounds. The inclusion equilibrium constants for several alcohols and aldehydes over β‐CD have been calculated through their UV‐vis spectra. The Gibbs free energy changes of β‐CD/substrates complexes (ΔG) have been calculated combined B3LYP/6‐31G(d)//ONIOM2(B3LYP/6‐31G(d):PM3) with semicontinuum solvation model. The difference of Gibbs free energy changes (ΔΔG) for the inclusion complexes formed via the intermolecular weak interactions e.g., hydrogen bond and electrostatic interaction was the reason why alcohol and aldehyde compounds could be selectively separated. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Nd-Cr/Al_2O_3催化剂上苯直接氧化制苯酚的动力学研究

研究了苯直接氧化制苯酚反应的动力学行为。推测了Nd-Cr/Al2O3催化剂上过氧化氢氧化苯为苯酚的反应过程,建立了该反应动力学数学模型,模型很好的解释了实验结果。结果表明,在实验条件下,该羟基化反应对反应物苯、氧化剂过氧化氢和催化剂用量都是一级反应,反应的活化能为24.41 kJ/mol。     

氢氛还原法制备氧化铁/膨润土 复合材料及其表征研究

以膨润土和硝酸铁为原料,采用氢氛还原法制备Fe₃O₄/膨润土复合材料,并采用X射线衍射（XRD）、扫描电子显微镜（SEM）和电子能谱（EDS）做表征分析。通过实验得到最佳的工艺条件：n（OH^-）∶n（Fe³⁺）=1∶1、铁土比为10 mmol/g、还原温度为200 ℃、还原时间为30 min。制备的Fe₃O₄/膨润土具有良好的类Fenton催化性能、稳定性与磁分离性能。制备过程中铁元素化合物能够有效固载在膨润土上,并在氢气还原作用下转化为Fe3O4,所得Fe3O4/膨润土是结构分散、孔隙明显、物化形态优良的催化复合材料。     

Regulation of Neuroinflammatory Signaling by PPARγ Agonist in Mouse Model of Diabetes

Many relevant studies, as well as clinical practice, confirm that untreated diabetes predisposes the development of neuroinflammation and cognitive impairment. Having regard for the fact that PPARγ are widely distributed in the brain and PPARγ ligands may regulate the inflammatory process, the anti-inflammatory potential of the PPARγ agonist, pioglitazone, was assessed in a mouse model of neuroinflammation related with diabetes. In this regard, the biochemical and molecular indicators of neuroinflammation were determined in the hippocampus and prefrontal cortex of diabetes mice. The levels of cytokines (IL-1β, IL-6, and TNF) and the expression of genes (Tnfrsf1a and Cav1) were measured. In addition, behavioral tests such as the open field test, the hole-board test, and the novel object recognition test were conducted. A 14-day treatment with pioglitazone significantly decreased IL-6 and TNFα levels in the prefrontal cortex and led to the downregulation of Tnfrsf1a expression and the upregulation of Cav1 expression in both brain regions of diabetic mice. Pioglitazone, by targeting neuroinflammatory signaling, improved memory and exploratory activity in behavioral tests. The present study provided a potential theoretical basis and therapeutic target for the treatment of neuroinflammation associated with diabetes. Pioglitazone may provide a promising therapeutic strategy in diabetes patients with muffled of behavioral activity.