Theoretical Study on the Adsorption and Hydrogenation Mechanism of 2-Methylthiophene over the Pt(111) Catalyst

The adsorption process and hydrogenation mechanisms of 2-methylthiophene on the Pt（111） surface have been elucidated using density functional theory（DFT）. The optimal adsorption sites of reactants, intermediates, and products as well as the activation energy and reaction energy of each elementary reactions were investigated. The results turned out that the 2-methylthiophene tilt to the Pt（111） catalyst with the C_1–C_2 double bond at the top site was the most stable. During the hydrogenation process, the heat of reaction almost located at the negative side, so dropping the temperature is good for the occurrence of hydrogenation process. The hydrogenation steps of mechanism take place along C_2→C_3→C_1→C_4→S→C_1 to generate the product of pentane-2-thiol, in which the first step with the highest energy barrier is the rate-determining step.

Efficient degradation of aqueous dichloromethane by an enhanced microbial electrolysis cell:Degradation kinetics,microbial community and metabolic mechanisms

Dichloromethane(DCM)has been listed as a toxic and harmful water pollutant,and its re moval needs attention.Microbial electrolysis cells(MECs)are viewed as a promising alterna tive for pollutant removal,which can be strengthened from two aspects:microbial inocula tion and acclimation.In this study,the MEC for DCM degradation was inoculated with the ac tive sludge enhanced by Methylobacterium rhodesianum H13(strain H13)and then acclimated in the form of a microbial fuel cell(MFC).Both the introduction of strain H13 and the initi ation in MFC form significantly promoted DCM degradation.The degradation kinetics were fitted by the Haldane model,with V_(max),K_(h),K_(i)and v_(max)values of 103.2 mg/L/hr,97.8 mg/L268.3 mg/L and 44.7 mg/L/hr/cm^(2),respectively.The cyclic voltammogram implies that DCM redox reactions became easier with the setup of MEC,and the electrochemical impedance spectrogram shows that the acclimated and enriched microbes reduced the charge transfe resistance from the electrode to the electrolyte.In the biofilm,the dominant genera shifted from Geobacter to Hyphomicrobium in acclimation stages.Moreover,Methylobacterium played an increasingly important role.DCM metabolism mainly occurred through the hydrolytic glutathione S-transferase pathway,given that the gene dcmA was identified rather than the dhlA and P450/MO.The exogenous electrons facilitated the reduction of GSSG,directly o indirectly accelerating the GSH-catalyzed dehalogenation.This study provides support fo the construction of an efficient and stable MEC for DCM removal in water environment.

Photo-triggered Intramolecular Radical Tandem Regioselective Alkylation/Cyclization of 1,6-Dienes with Redox-Active Esters Enabled by an EDA Complex

A photocatalyst-and metal-free radical tandem alkylation/cyclization between 1,6-dienes and redox-active esters has been devel-oped,affording a series of N-aryl pyrrolidine-2-ones in moderate to good yields.The transformation is driven by the formation of an electron-donor-acceptor(EDA)complex and a subsequent single electron transfer(SET)process.This photocatalyst-free protocol features excellent regioselectivity,mild conditions and broad substrate scope,providing a facile access to 3-alkyl-3,4-dimethyl-1-phe-nylpyrrolidin-2-one.

Highly selective kinetic resolution of D/L-syn-p-sulfone phenylserine catalyzed by D-threonine aldolase in two-phase ionic solvent

In the chemical synthesis of L-syn-p-methylsulfoxide phenylserine ethyl ester(D-ethyl ester),L-tartaric acid or enzymatic resolution is employed to resolve the racemate,and thus obtain the target compound,and the remaining isomer can be recycled to obtain the raw material.In this study,high-purity L-syn-p-methylsulfoxide phenylserine(L-syn-MPS)was obtained.The kinetics of the D-threonine aldolase enzymatic hydrolysis reaction reveals that D-syn-p-sulfoxylphenylserine resolves well in[BMIM][BF 4]ionic solvents.The D/L-syn-MPS racemate was resolved using a two-phase ionic solvent[BMIM][NTf 2]to afford L-syn-MPS(ee(enantiomeric excess)>99%)and a white solid in 41.7%yield.Therefore,this system is suitable for the separation of insoluble aldehydes and successfully avoids the condensation of hydroxyl aldehydes to form D-anti-MPS.

Release and uptake mechanisms of vesicular Ca^2+stores

Cells utilize calcium ions(Ca^2+)to signal almost all aspects of cellular life,ranging from cell proliferation to cell death,in a spatially and temporally regulated manner.A key aspect of this regulation is the compartmen-talization of Ca^2+in various cytoplasmic organelles that act as intracellular Ca^2+stores.Whereas Ca^2+release from the large-volume Ca^2+stores,such as the endoplasmic reticulum(ER)and Golgi apparatus,are preferred for signal transduction,Ca^2+release from the small-volume individual vesicular stores that are dispersed throughout the cell,such as lysosomes,may be more useful in local regulation,such as membrane fusion and individualized vesicular movements.Conceivably,these two types of Ca^2+stores may be established,maintained or refilled via distinct mechanisms.ER stores are refilled through sustained Ca^2+influx at ER-plasma membrane(PM)membrane contact sites(MCSs).In this review,we discuss the release and refilling mechanisms of intracellular small vesicular Ca^2+stores,with a special focus on lysosomes.Recent imaging studies of Ca2+release and organelle MCSs suggest that Ca^2+exchange may occur between two types of stores,such that the small stores acquire Ca^2+from the large stores via ER-vesicle MCSs.Hence vesicular stores like lysosomes may be viewed as secondary Ca^2+stores in the cell.

Enzyme-electrolytic degradation of dichloromethane: Efficiency, kinetics and mechanism

Enzymatic electrolysis cell(EEC)has advantages over microbial electrolysis cell(MEC)due to the needless of microbe inoculation and high-efficiency of enzymatic reaction.In this study,an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane(CH2Cl2)was utilized as a model pollutant.The results indicate that the degradation efficiency of CH2Cl2 after 2 hr reaction in the EEC was almost100%,which was significantly higher than that with enzyme(51.1%)or current(19.0%).The current induced the continuous regeneration of reduced glutathione(GSH),thus CH2Cl2 was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination,and successively formed monochloromethane(CH3Cl)and methane(CH4).The kinetic result shows that with a current of 15 mA,the maximum specific degradation rate of CH2Cl2(3.77×10-3 hr-1)was increased by 5.7 times.The optimum condition for CH2Cl2 dechlorination was also obtained with pH,current and temperature of 7.0,15 mA and 35°C,respectively.Importantly,this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC,providing a possible treatment technology for halogenated organic pollutants.

Recent advances of small-molecule fluorescent probes for detecting biological hydrogen sulfide

H_(2)S is well-known as a colorless,acidic gas,with a notoriously rotten-egg smell.It was recently revealed that H_(2)S is also an endogenous signaling molecule that has important biological functions,however,most of its physiology and pathology remains elusive.Therefore,the enthusiasm for H_(2)S research remains.Fluorescence imaging technology is an important tool for H_(2)S biology research.The development of fluorescence imaging technology has realized the study of H_(2)S in subcellular organelles,facilitated by the development of fluorescent probes.The probes reviewed in this paper were categorized according to their chemical mechanism of sensing and were divided into three groups:H_(2)S reducibility-based probes,H_(2)S nucleophilicity-based probes,and metal sulfide precipitation-based probes.The structure of the probes,their sensing mechanism,and imaging results have been discussed in detail.Moreover,we also introduced some probes for hydrogen polysulfides.

Sinucrassins A-K, Casbane-type Diterpenoids from the South China Sea Soft Coral Sinularia crassa

A detailed chemical study on the Hainan soft coral Sinularia crass has resulted in the isolation and characterization of eleven cas-bane-type diterpenoids,named sinucrassins A-K(1-11),along with six known related ones(12-17).Their structures were elucidated by extensive spectroscopic analyses and comparison with the reported data.The absolute configurations of new compounds were determi ned by the X-ray diffracti on analysis and computer-assisted structural elucidati on in eluding 13C NMR data calculati on and time-dependent density functional theory/electronic circular dichroism calculation.

Application of Enzymatic Promiscuity in Pharmaceutical Synthesis:Papain-catalyzed One-pot Synthesis of 1,4-Dihydropyridine Calcium Channel Antagonists and Derivatives

A new method for the synthesis of 1,4-dihydropyridine(1,4-DHP)calcium channel antagonists felodipme, nitrendipine and their derivatives via papain-catalyzed three-component reactions of aldehyde,methyl acetoacetate and ethyl 3-aminocrotonate was developed.Operational simplicity,mild reaction conditions and eco-friendliness are the key features of this protocol.

Degradation of dichloromethane by an isolated strain Pandoraea pnomenusa and its performance in a biotrickling filter

A strain Pandoraea pnomenusa LX-1 that uses dichloromethane （DCM） as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation （5.35 mg/（L.hr）） was achieved under cultivation at 32.8℃, pH 7.3, and 0.66% NaC1. The growth and biodegradation processes were well fitted by Haldane＇s kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr^-1 and 0.856 hr^-1, respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components （benzene, toluene and chlorobenzene）. The carbon recovery （52.80%-94.59%） indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order： mixed 〉 oxygen 〉 iron 〉 sulfate 〉 nitrate. The highest dechlorination rate was 0.365 mg C1-/（hr.mg biomass）, obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%-85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.

Photoinduced NaI-Promoted Radical Borylation of Alkyl Halides and Pseudohalides

Main observation and conclusion A method for photoinduced NaI-promoted radical borylation of aliphatic halides and pseudohalides with bis(catecholato)diboron(B_(2)cat_(2))as the boron source is introduced.The borylation reaction is operationally simple and shows high functional group tolerance and broad substrate scope.Preliminary mechanistic studies suggest that the reaction proceeds through S_(N)2-based radical-generation strategy.

Polyoxygenated Cembranoids from Soft Coral Lobophytum Crassum and Their Anti-tumoral Activities

Main observation and conclusion Four new cembranoids,6-oxo-cembrene-A(1),lobocrassins G-H(2-3),and 14-epi-lobophytolide B(4),along with eight known re-lated compounds(5-12),were isolated from the South China Sea soft coral Lobophytum crassum.Their structures were established by extensive spectroscopic analysis and by comparison of the spectral data with those reported in the literatures.The absolute stere-ochemistry of 14-epi-lobophytolide B(4)was established by time-dependent density functional theory electronic circular dichroism(TDDFT-ECD)calculations,whereas that of three known metabolites(6,11 and 12)was also determined,for the first time,by using modified Mosher's method and/or X-ray diffraction analyses.In bioassay,the cembranoids 6,7 and 12 showed significant an-ti-tumoral activity against A549,HT-29,SNU-398 and Capan-1 tumor cell lines with IC_(50) values ranging from 1.5 to 7.4μmol/L.A pre-liminary structure-activity relationship was also discussed.

Morpholine triflate promoted one-pot,four-component synthesis of dihydropyrano[2,3-c]pyrazoles

A one-pot, four-component reaction of ethyl acetoacetate, hydrazine hydrate, aldehydes, and malononitrile was discussed using Lewis acid catalyst morpholine triflate （MorT） to afford a series of dihydropyrano[2,3-c]pyrazoles, which were generally catalyzed by organic alkalis. Moderate to excellent yields, no chromatographic purification, and evasion of environmentally hazardous solvents in the reaction process make this protocol very useful for academia and industry.

One-pot Multicomponent Synthesis of Highly Functionalized 1,4-Dihydropyridines Using Porcine Pancreatic Lipase

A series of highly timctionalized 1,4-dihydropyridines was synthesized via one-pot multicomponent reactions of aromatic aldehyde,malononitrile and N-methyl-1-(methylthio)-2-nitroethenamine using Porcine pancreatic lipase(PPL)as catalyst in DMSO.This protocol is featured by mild reaction conditions,simple operation and environmental acceptability.

Visible-light-promoted radical alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester: Synthesis of oxazolines

An efficient photocatalytic alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester has been developed. The transformation is taken advantage of alkyl radicals to attack allylic amide with the assist of inexpensive rose bengal as photocatalyst to prepare a series of alkyl substituted oxazolines in moderate to excellent yields. High regioselectivity, operational safety, mild conditions and excellent substrate generality give this protocol broad application prospects.

New Cembrane-Type Diterpenoids from the South China Sea Soft Coral Sinularia nanolobata

In the present study,nine new cembrane-type diterpenoids,namely ximaonanolobatins A—I(1—9),together with six related known analogs(10—15)and four known tetraprenylated alkaloids malonganenones D,E,H,and K(16—19)were isolated from the soft coral Sinularia nanolobata collected off the Ximao Island in the South China Sea.The structures of 1—9 were robustly established by a combination of detailed spectroscopic analyses,chemical reactions,quantum mechanical(QM)-NMR methods,biogenetic consideration,and the comparison with those literature data.The absolute configuration of 1 was confirmed by X-ray diffraction analysis,and the absolute configuration of 2 was determined by QM-NMR calculations and chemical transformation.In addition,the absolute configuration of 3 was determined using the modified Mosher's method.All these isolates were evaluated for their anti-inflammatory and anti-tumor activities.The results showed that only compound 15 exhibited potential anti-inflammatory effect against LPS-induced TNF-αrelease in RAW264.7 macrophages with an IC50 value of 12.6μmol/L.

In vitro characterization of a nitro-forming oxygenase involved in 3-(trans-2’-aminocyclopropyl)alanine biosynthesis

In vitro characterization experiments revealed the formations of 3-(trans-2’-aminocyclopropyl)alanine((3-Acp)Ala)and 3-(trans-2’-nitrocyclopropyl)alanine((3-Ncp)Ala)are originated via two homologous proteins,BelK and HrmI,which regioselectively catalyze the N𝜀-oxygenation of l-lysine.The two enzymes belong to the emerg-ing heme-oxygenase-like diiron oxidase and oxygenase(HDO)superfamily and the catalytic center of BelK is validated by homology modeling and site-directed mutations.Based on the in vitro characterization,the biosyn-thetic pathways of(3-Acp)Ala and(3-Ncp)Ala are proposed.

Marine alkaloids as the chemical marker for the prey–predator relationship of the sponge Xestospongia sp.and the nudibranch Jorunna funebris

The dietary relationship study between marine sponge Xestospongia sp.and its nudibranch predators Jorunna funebris based on the discovery of isoquinolinequinones has long been studied.In this study,chemical investigation of the sponge Xestospongia sp.and nudibranch J.funebris from the South China Sea yielded a new marine alkaloid neopetroside C(1),together with nine known alkaloids(2-10).The chemical structures of all the compounds were elucidated by extensive spectroscopic analysis.Neopetroside C(1)featured a riboside of nicotinic acid with a rareα-N glycosildic linkage and an acyl residue of(Z)-2-methylbut-2-enoic acid attached to C-5′.The plausible chemical ecology relationship between sponge Xestospongia sp.and its nudibranch predator J.funebris was proposed based on the biogenetic relationship of the common marine alkaloids.The observation of two structural fragments,(Z)-2-methylbut-2-enoyloxy and trigonelline groups in both sponge and nudibranch,indicated that nudibranch might uptake chemicals from sponge and then modify and transform them into chemical weapons to defend against predators.

Ocellatuspyrones A‒G,new antibacterial polypropionates from the Chinese mollusk Placobranchus ocellatus

Marine invertebrates serve as rich sources of secondary metabolites with intriguing chemical diversities and a wide spectrum of biological activities.Particularly,marine shell-less sacoglossan mollusks have attracted much attentions due to the fact that mollusks apply complex metabolites as chemical defense agents against to their predators.With the purpose of discovering bioactive secondary metabolites to develop marine-derived medicines from the South China Sea,we have conducted a chemical study on the photosynthetic mollusk Placobranchus ocellatus.As a result,seven newγ-pyrone polypropionates,namely(±)-ocellatuspyrone A(1),(±)-ocellatuspyrone B(2),and ocellatuspyrones C−G(5,9−12),along with fve known polypropionates,have been isolated and characterized from the South China Sea photosynthetic mollusk Placobranchus ocellatus.Extensive spectroscopic analysis,single crystal X-ray difraction analysis,modifed Mosher’s method,ECD comparison,CD exciton chirality method,TDDFT-ECD calculation,and chemical conversion were used to determine the structures and absolute confgurations of the new compounds and the stereochemistry of undefned known compounds 4,6 and 7.All these isolated polypropionates were evaluated in bioassays for their biological activities,including antibacterial,neuroprotective efect,anti-infammatory,PTP1B inhibitory,and antiviral activities.Compounds 7,8 and 11 were found for the frst time to show antibacterial activity against fsh pathogenic bacteria Streptococcus parauberis(the main pathogen causing fsh streptococcal infections and acute death)with MIC values of 35.8,34.2,and 37.4μg/mL,respectively,which might be potential novel antibacterial agents for the treatment of fsh infectious diseases.

Quantum hydrogen tunneling promoting halogen-atom and group transfer chemistry

A quantum-hydrogen-tunneling-controlled halogen-atom and group transfer strategy has been successfully developed to generate carbon radicals by using the substituted cyclohexadiene as the abstractor under mild photochemical conditions,in which alkyl and aryl halides as well as numerous alcohol and thiol analogues can be activated.Mechanism investigation unveiled that this process is inhibited from thermodynamic and kinetic effects but is rendered successful through quantum tunneling.