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• Combi-CLEAs of glycerol dehydrogenase and NADH oxidase were prepared for in situ NAD+ regeneration. • Adjacent dispersion of two enzymes may lead to the quick uptake of NAD+ and achieve the high-speed NAD+ regeneration. • The conversion of glycerol in combi-CLEAs reaches 4.60%, which is 2.5 folds of the free enzyme (1.85%). Cofactor regeneration is an important method to avoid the consumption of large quantities of oxidized cofactor NAD+ in enzyme-catalyzed reactions. Herein, glycerol dehydrogenase (GDH) and NADH oxidase preparations by aggregating enzymes with ammonium sulphate followed by cross-linking formed aggregates for effective regeneration of NAD+. After optimization, the activity of combi-CLEAs and separate CLEAs mixtures were 950 and 580 U/g, respectively. And the catalytic stability of combi-CLEAs against pH and temperature was superior to the free enzyme mixture. After ten cycles of reuse, the catalytic efficiency could still retain 63.3% of its initial activity, indicating that the constructed combi-CLEAs system had excellent reusability. Also, the conversion of glycerol to 1,3-dihydroxyacetone (DHA) was improved by the constructed NAD+ regeneration system, resulting in 4.6%, which was 2.5 times of the free enzyme system. Thus, wide applications of this co-immobilization method in the production of various chiral chemicals could be expected in the industry for its high efficiency at a low cost. [ABSTRACT FROM AUTHOR]

Enzymatic NADP+ regeneration is a promising approach to produce valuable chemicals under economic conditions. Among all the enzymatic routes, using water-forming NADH oxidase is an ideal one because there is no by-product. However, most NADH oxidases have a low specific activity to NADPH. In this work, a thermostable NADH oxidase from Lactobacillus rhamnosus (LrNox) was rationally engineered to switch its specificity from NADH to NADPH. The results show that mutants D177A, G178R, D177A/G178R, D177A/G178R/L179S improved the NADPH activity by a factor of 4–6. The highest NADPH catalytic efficiency (K cat /K m 223.71 S−1 μm−1, 47.6-fold higher than wild-type LrNox) and 51% of NADH activity retention were achieved by replacing the single amino acid Leu179 for serine (L179S) in LrNox. Modeling of L179S-NADPH complex reveals that the phosphate group of NADPH interacts with the hydroxyl of Ser179 with a strong hydrogen bond and several shorter hydrogen bonds with the amino group of Lys185 could stabilize the binding of NADPH in the L179S mutant. This work provides an efficient method for converting NAD(P)H specificity and shows that L179S mutant is a potential and efficient auxiliary enzyme for NADP+ regeneration. Unlabelled Image • Conserved loop region (Asp177-Ala184) is important for NAD(P)H binding. • Mutant L179S exhibits 47.7-fold of catalytic efficiency towards NADPH compared with the wild-type LrNox. • Hydroxyl of introduced Ser179 interacts the phosphate motif of NADPH with a strong hydrogen bond. • The hydrogen bonds formed between Lys185 and NADPH were shortened by introducing Ser179. [ABSTRACT FROM AUTHOR]

Cysteine, a critical residue for catalytic process but also vulnerable to oxidative damage, was conventionally expressed as a buried catalytic site in most redox enzymes. In the present work, specific surface-exposed sites of a NADH oxidase from Lactobacillus rhamnosus (LrNox) were selected and mutated to cysteine to investigate its effects on catalytic function because LrNox has a buried catalytic cysteine but no surface-exposed one. The results showed that exception of the sites on dimer interface, the activities of LrNox mutants were improved to vary degrees when the polar uncharged and alanine residues were mutated to cysteine. But the cysteine mutations of polar charged and nonpolar residues except alanine showed obvious decline in catalytic activity. Substituting of Ala85 and Thr96 with other residues suggested that the cysteine mutation showed the highest activity. Structural analysis suggested that even a single cysteine mutation on the specific non-conserved surface area of LrNox could induce changes on the conformation of catalytic cysteine and lower the activation free energy to improve the catalytic activity. Unlabelled Image • Cysteine was firstly introduced onto the surface of NADH oxidase which has a catalytic cysteine residue. • The activity of NADH oxidase was improved 2.76 folds by mutating Thr96 to cysteine. • The catalytic function of surface cysteine mutants is highly correlated to the polarity and charge of the selected residue. [ABSTRACT FROM AUTHOR]

A novel nicotinamide adenine dinucleotide (NADH) oxidase from Streptococcus mutans ATCC 25175 (SmNox) was cloned and overexpressed in Escherichia coli BL21 (DE3). Sequence analysis revealed an open reading frame of 1374 bp, capable of encoding a polypeptide of 457 amino acid residues. The molecular mass of the purified SmNox was estimated to be ∼49.9 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified SmNox had the highest specific activity of 281.2 U·mg −1 at optimal pH and temperature of 7.0 and 35 °C, with a K m of 57.7 μM and a V max of 154.3 U·mg −1 . The good stability at room temperature was observed. Homology modeling and substrate docking were performed to evaluate the catalytic characteristics. The results indicated that Nicotinamide ring of NADH extends vertically toward to re-face of coenzyme (FAD), and the specific conformation of NADH suggested that the charges transfer in SmNox complex could be easier than in its homologous enzyme (LbNox) under alkaline environment. The characterization of the SmNox indicated it has potential in industrial regeneration of coenzyme NAD + for coupling with dehydrogenases. [ABSTRACT FROM AUTHOR]

Abstract: An efficient method of ligand-free Cu-catalyzed oxidative decarboxylative homocoupling of aryl propiolic acids was developed. When CuI was employed as the catalyst and I2 as the oxidant, the decarboxylative homocoupling reaction for Csp–Csp bond formation in DMSO underwent smoothly to afford the corresponding 1,4-disubstituted 1,3-dialkynes in good to excellent yields without any organic ligands. This catalytic system was applicable to aryl propiolic acids bearing different steric, electronic, and functional groups. [Copyright &y& Elsevier]

• A novel water-forming flavin oxidoreductase was first expressed and characterized. • A rate-limiting Thr29 was identified and confirmed to be employed to improve its activity. • The distance between FMN and NADH was shortened by introducing a small side chain containing residue into position 29. Enzyme-catalyzed cofactor regeneration is a significant approach to avoid large quantities consumption of oxidized cofactor, which is vital in a variety of bioconversion reactions. NADH: FMN oxidoreductase is an ideal regenerating enzyme because innocuous molecular oxygen is required as an oxidant. But the by-product H 2 O 2 limits its further applications at the industrial scale. Here, novel NADH: FMN oxidoreductase (LrFOR) from Lactobacillus rhamnosus comprised of 1146 bp with a predicted molecular weight of 42 kDa was cloned and overexpressed in Escherichia coli BL21 (DE3). Enzyme assay shows that the purified recombinant LrFOR has both the NADPH and NADH oxidation activity. Biochemical characterizations suggested that LrFOR exhibits the specific activity of 39.8 U·mg−1 with the optimal pH and temperature of 5.6 and 35 °C and produces H 2 O instead of potentially harmful peroxide. To further study its catalytic function, a critical Thr29 residue and its six mutants were investigated. Mutants T29G, T29A, and T29D show notable enhancement in activities compared with the wild type. Molecular docking of NADH into wild type and its mutants reveal that a small size or electronegative of residue in position29 could shorten the distance of NADH and FMN, promoting the electrons transfer and resulting in the increased activity. This work reveals the pivotal role of position 29 in the catalytic function of LrFOR and provides effective catalysts in NAD+ regeneration. [ABSTRACT FROM AUTHOR]

An efficient approach to decarboxylative C3-acylation of benzothiophenes or benzofurans with α-oxocarboxylic acids via palladium-catalyzed C–H bond activation was developed. This method was compatible with a variety of functional groups and provided an attractive route to 3-acylbenzothiophenes and 3-acylbenzofurans in good to high yields. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions of CdSO4 with tetrakis(4-pyridyl)cyclobutane (tpcb) and 1,3-benzenedicarboxylic acid (1,3-H2BDC) or 5-nitro-1,3-benzenedicarboxylic acid (5-NO2-1,3-H2BDC) resulted in the formation of two coordination polymers [Cd(tpcb)0.5(1,3-BDC)]n (1) and {[Cd2(tpcb)(5-NO2-1,3-BDC)2(OH2)2]·4H2O}n (2), respectively. Compounds 1 and 2 were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. 1 and 2 exhibit two different types of two-fold interpenetrating 3D architectures with (66)2(64 ·82) and (52 ·8)(54 ·6∙8)(4·53 ·62 ·7·82 ·10) Schläfli symbols, respectively. Their thermal and photoluminescent properties were also investigated. [ABSTRACT FROM AUTHOR]

• Integrated S-MoSe 2 / multi-channel carbon nanofibers is fabricated via in situ selenation process and sulfur deposition. • Accelerated charge delocalization and reduced adsorption energy barrier of sodium ions are achieved. • The advanced rate and high energy density for sodium-ion half/full batteries are exhibited. • S doing is beneficial for sodium ion adsorption and denser conduction band distribution. Constructing structures suitable for sodium ion deintercalation is of great significance for the innovation of sodium-ion batteries (SIBs) materials. In this work, multi-channel carbon nanofibers (MCFs) supported sulfur-doped MoSe 2 (S-MoSe 2) nanosheets are fabricated via modified electrospinning followed by in situ selenation process and sulfur deposition. The integrated S-MoSe 2 /MCFs can effectively buffer the volume stress caused by sodium ion (de)intercalation and provide abundant ion/electron migration transportations. As anode for SIBs, the S-MoSe 2 /MCFs demonstrates good rate capability, delivering 308.3 mAh g–1 at 10 A g–1. Additionally, it exhibits cycling stability, maintaining 336.2 mAh g–1 after enduring 1000 cycles at 5 A g–1. These attributes are direct result of the S-MoSe 2 /MCFs' structural stability and better electronic conductivity, as confirmed by diffusion analysis. When paired with Na 3 V 2 (PO 4) 2 O 2 F cathode, the full cell also achieves a high energy density of 102.2 Wh kg–1. The detailed theoretical calculation of the different surface sites of S-MoSe 2 confirming the high performance SIBs is due to the enhanced adsorption and diffusion performance of Na ion bought by the S doping. The study has provided substantial evidence supporting the creation of a network of rapid ion and electron migration pathways. This network effectively facilitates sodium-ion storage and paves the way for exploring the high-performance transition metal dichalcogenides (TMDs)-based electrodes in SIBs. Integrated S-MoSe 2 /MCFs with accelerated charge delocalization and reduced adsorption energy barrier of sodium ions show advanced sodium-ion half/full batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: This work reported that Suzuki–Miyaura coupling reactions of arylboronic acid with aryl bromide or iodides were mediated by Pd(OAc)2 and 4-(benzylthio)-N,N,N-trimethylbenzenammonium chloride in the presence of Na2CO3 in water under the mild conditions. The corresponding Suzuki–Miyaura coupling products were obtained in good to excellent yields. [Copyright &y& Elsevier]