Thiol Redox and pKa Properties of Mycothiol,the Predominant Low‐Molecular‐Weight Thiol Cofactor in the Actinomycetes

The thiol pK_a and standard redox potential of mycothiol, the major low‐molecular‐weight thiol cofactor in the actinomycetes, are reported. The measured standard redox potential reveals substantial discrepancies in one or more of the other previously measured intracellular parameters that are relevant to mycothiol redox biochemistry.     

Novel Redox-Dependent Esterase Activity (EC 3.1.1.2) for DJ-1: Implications for Parkinson’s Disease

Mutations the in human DJ-1 (hDJ-1) gene are associated with early-onset autosomal recessive forms of Parkinson’s disease (PD). hDJ-1/parkinsonism associated deglycase (PARK7) is a cytoprotective multi-functional protein that contains a conserved cysteine-protease domain. Given that cysteine-proteases can act on both amide and ester substrates, we surmised that hDJ-1 possessed cysteine-mediated esterase activity. To test this hypothesis, hDJ-1 was overexpressed, purified and tested for activity towards 4-nitrophenyl acetate (pNPA) as µmol of pNPA hydrolyzed/min/mg·protein (U/mg protein). hDJ-1 showed maximum reaction velocity esterase activity (V_max = 235.10 ± 12.00 U/mg protein), with a sigmoidal fit (S_0.5 = 0.55 ± 0.040 mM) and apparent positive cooperativity (Hill coefficient of 2.05 ± 0.28). A PD-associated mutant of DJ-1 (M26I) lacked activity. Unlike its protease activity which is inactivated by reactive oxygen species (ROS), esterase activity of hDJ-1 is enhanced upon exposure to low concentrations of hydrogen peroxide (<10 µM) and plateaus at elevated concentrations (>100 µM) suggesting that its activity is resistant to oxidative stress. Esterase activity of DJ-1 requires oxidation of catalytic cysteines, as chemically protecting cysteines blocked its activity whereas an oxido-mimetic mutant of DJ-1 (C106D) exhibited robust esterase activity. Molecular docking studies suggest that C106 and L126 within its catalytic site interact with esterase substrates. Overall, our data show that hDJ-1 contains intrinsic redox-sensitive esterase activity that is abolished in a PD-associated mutant form of the hDJ-1 protein.     

Insights into corrosion in dye solar cells

The main issue in using low cost metals in dye solar cells is the corrosion caused by the liquid electrolyte. Contrary to typical applications of metals, the adverse effects of corrosion in dye solar cells are related to irreversible depletion of charge carriers from the electrolyte rather than consumption of the metal itself. It is calculated that the penetration rate due to corrosion should not exceed 10⁻⁴ mpy (a couple of nanometers per year) to ensure device lifetime longer than 1 year. This is 10 000 times slower rate than what is considered to be a general benchmark value for very low corrosion rate in the field of corrosion science and has a major effect on how corrosion should be investigated in the case of dye solar cells. Different methods, their applicability, and limitations to investigate corrosion in dye solar cells are evaluated here. The issue with most techniques is that they can detect metals that are clearly corroding, but they have significant limitations in proving a metal stable. Our investigation shows that the most reliable information on corrosion is obtained from complete dye solar cells that are exposed to working conditions. A combination of color analysis of the electrolyte to such measurement is proposed as a means to extrapolate future performance of the cells and estimate potential lifetimes of the dye solar cells in regards to corrosion. Copyright © 2014 John Wiley & Sons, Ltd.     

通过磁化提高电解二氧化锰放电性能

介绍了J.Leddy和J.P.Tesene进行的通过磁化作用改变电解二氧化锰在碱性锌锰电池中的放电机理的试验,实验结果表明磁化可提高碱锰电池放电性能和可充性,讨论了该项技术的应用领域和市场前景。     

The Role of Vitamin D in Supporting Health in the COVID-19 Era

The genomic activity of vitamin D is associated with metabolic effects, and the hormone has a strong impact on several physiological functions and, therefore, on health. Among its renowned functions, vitamin D is an immunomodulator and a molecule with an anti-inflammatory effect, and, recently, it has been much studied in relation to its response against viral infections, especially against COVID-19. This review aims to take stock of the correlation studies between vitamin D deficiency and increased risks of severe COVID-19 disease and, similarly, between vitamin D deficiency and acute respiratory distress syndrome. Based on this evidence, supplementation with vitamin D has been tested in clinical trials, and the results are discussed. Finally, this study includes a biochemical analysis on the effects of vitamin D in the body’s defense mechanisms against viral infection. In particular, the antioxidant and anti-inflammatory functions are considered in relation to energy metabolism, and the potential, beneficial effect of vitamin D in COVID-19 is described, with discussion of its influence on different biochemical pathways. The proposed, broader view of vitamin D activity could support a better-integrated approach in supplementation strategies against severe COVID-19, which could be valuable in a near future of living with an infection becoming endemic.     

Robust proton exchange membrane for vanadium redox flow batteries reinforced by silica-encapsulated nanocellulose

High ion selectivity and mechanical strength are critical properties for proton exchange membranes in vanadium redox flow batteries. In this work, a novel sulfonated poly(ether sulfone) hybrid membrane reinforced by core-shell structured nanocellulose (CNC-SPES) is prepared to obtain a robust and high-performance proton exchange membrane for vanadium redox flow batteries. Membrane morphology, proton conductivity, vanadium permeability and tensile strength are investigated. Single cell tests at a range of 40–140 mA cm⁻² are carried out. The performance of the sulfonated poly(ether sulfone) membrane reinforced by pristine nanocellulose (NC-SPES) and Nafion® 212 membranes are also studied for comparison. The results show that, with the incorporation of silica-encapsulated nanocellulose, the membrane exhibits outstanding mechanical strength of 54.5 MPa and high energy efficiency above 82% at 100 mA cm⁻², which is stable during 200 charge-discharge cycles.     

Reconstructing a Flavodoxin Oxidoreductase with Early Amino Acids

Primitive proteins are proposed to have utilized organic cofactors more frequently than transition metals in redox reactions. Thus, an experimental validation on whether a protein constituted solely by early amino acids and an organic cofactor can perform electron transfer activity is an urgent challenge. In this paper, by substituting “late amino acids (C, F, M, T, W, and Y)” with “early amino acids (A, L, and V)” in a flavodoxin, we constructed a flavodoxin mutant and evaluated its characteristic properties. The major results showed that: (1) The flavodoxin mutant has structural characteristics similar to wild-type protein; (2) Although the semiquinone and hydroquinone flavodoxin mutants possess lower stability than the corresponding form of wild-type flavodoxin, the redox potential of double electron reduction E_m,7 (fld) reached −360 mV, indicating that the flavodoxin mutant constituted solely by early amino acids can exert effective electron transfer activity.     

毕赤酵母合成S-腺苷甲硫氨酸过程谷胱甘肽流量分析与控制

S-腺苷甲硫氨酸(S-adenosyl-L-methionine,SAM)是一种具有广阔应用前景的活性氨基酸,利用毕赤酵母催化合成是SAM主要生产方法,但SAM可被细胞转化为还原型谷胱甘肽(glutathione reduced,GSH),后者可进一步转化为氧化型谷胱甘肽(glutathione oxidized,GSSG)。该研究分析了SAM合成过程中谷胱甘肽总量的动态变化,并基于GSSG/GSH偏移,揭示了胞内氧化还原势与GSH流量变化的相关性。最后添加抗氧化剂维生素C,通过降低胞内SAM→GSH流量及改善细胞活性,进一步提高SAM产率。     

Structure‐Based Mechanism of Oleate Hydratase from Elizabethkingia meningoseptica

Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration.     

细菌Enterobacter dissolvens的直流电解刺激过程

以葡萄糖为唯一碳源,研究了细菌Enterobacter dissolvens在直流电条件下的生长和代谢过程. 实验结果表明,当使用盐桥屏蔽电极反应时,细胞生长曲线和葡萄糖代谢速率基本不受电流强度的影响,而当采用铂丝电极时,反应体系中发生水解反应,采用10 mA电流通电12 h后,菌液中细胞的脱氢酶比活力和葡萄糖降解率分别为对照的1.98倍和1.48倍,细胞生长亦有所加快,但在其活力下降时出现大量死亡. 扫描电镜照片显示细胞结构受到明显破坏,并发生细胞膜穿孔现象,这表明可能受到了过氧化氢等阳极水解中间产物的刺激作用.