Biomass valorization via electrocatalytic carbon–carbon bond cleavage

Renewable electrocatalytic upgrading of biomass feedstocks into valuable chemicals is one of the promising strategies to relieve the pressure of traditional energy-based systems.Through electrocatalytic carbon–carbon bond cleavage of high selectivity,various functionalized molecules,such as organic acids,amides,esters,and nitriles,have great potential to be accessed from biomass.However,it has merely received finite concerns and interests in the biorefinery.This review first showcases the research progress on the electrocatalytic conversion of lipid/sugar-and lignin-derived molecules(e.g.,glycerol,mesoerythritol,xylose,glucose,1-phenylethanol,and cyclohexanol)into organic acids via specific carbon–carbon bond scission processes,with focus on disclosing reaction mechanisms,recognizing actual active species,and collecting feasible modification strategies.For the guidance of further extensive studies on biomass valorization,organic transformations via a variety of reactions,including decarboxylation,ring-opening,rearrangement,reductive hydrogenation,and carboxylation,are also disclosed for the construction of similar carbon skeletons/scaffolds.The remaining challenges,prospective applications,and future objectives in terms of biomass conversion are also proposed.This review is expected to provide references to develop renewed electrocatalytic carbon–carbon bond cleavage transformation paths/strategies for biomass upgrading.

Autophagy-related protein PlAtg3 participates in vegetative growth,sporangial cleavage,autophagy and pathogenicity of Peronophythora litchii

Litchi downy blight,caused by the plant pathogenic oomycete Peronophythora litchii,is one of the most devastating diseases on litchi and resulted in huge economic losses.Autophagy plays an essential role in the development and pathogenicity of the filamentous fungi.However,the function of autophagy in oomycetes remain elusive.Here,an autophagy-related protein Atg3 homolog PlAtg3 was identified and characterized in P.litchii.The absence of PlATG3 through the CRISPR/Cas9 gene replacement strategy compromised vegetative growth and sexual/asexual development.Cytological analyses revealed that the deletion of PlATG3 impaired autophagosome formation with monodansylcadaverine(MDC)staining and significantly disrupted zoospore release due to defects of sporangial cleavage with FM4-64 staining.Atg8 is considered to be an autophagy marker protein in various species.Western blot analysis indicated that PlAtg3 is involved in degradation of PlAtg8-PE.Interestingly,PlAtg3 was unable to interact with PlAtg8 in yeast two hybrid(Y2H)assays,possibly due to the absence of the Atg8 family interacting motif(AIM)in PlAtg3.Furthermore,pathogenicity assays revealed that the deletion of PlATG3 considerably reduced the virulence of P.litchii.Taken together,our data reveal that PlAtg3 plays an important role in radial growth,asexual/sexual development,sporangial cleavage and zoospore release,autophagosome formation,and pathogenicity in P.litchii.This study contributes to a better understanding of the pathogenicity mechanisms of P.litchii and provides insights for the development of more effective strategies to control oomycete diseases.

Mineral cleavage nature and surface energy: Anisotropic surface broken bonds consideration

The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation results, the cleavage natures of these minerals were analyzed, and the relationship between surface broken bonds density and surface energy was also established. The results show that the surface broken bonds properties could be used to predict the cleavage nature of most of minerals, and the predicted cleavage planes agree well with those reported in previous literature. Moreover, this work explored a rule that, surface broken bonds density is directly related to surface energy with determination coefficient（R2） of over 0.8, indicating that the former is a dominant factor to determine the latter. Therefore, anisotropic surface broken bonds density can be used to predict the stability of mineral surface and the reactivity of surface atoms.

Optimizing Yanbian Cow Oocytes Mature in vitro and Cleavage System after Nuclear Transfer Based on Uniform Design

[Objective] The aim was to optimize Yanbian cow oocytes mature in vitro and cleavage system after nuclear transfer based on uniform design. [Method] Oocytes were recovered by aspiration method, and oocytes were matured in vitro （IVM） with different conditions, and then carried out nucleus transfer, fusion, activation and in vitro culture （IVC） of embryo. Effects of ovary storage temperature, maturation time and follicular diameter size on in vitro maturation and cleavage rates of cow oocytes were compared. [ Result] The best conditions of IVM of Yanbian cow oocytes was that： the oocytes of 8 mm diameter were matured in vitro for 24 hours when the ovaries were stored at 26℃ or 31 ℃. The best cleave conditions after nucleus transfer of oocytes was that： the oocytes of 6 mm or 8 mm diameter were cultured in vitro for 24 hours when the ovaries were stored at 26℃. [ Conclusion] The result has some reference to Yanbian cow and other cow breeding and population expanding propagation.

Efficient and Convenient Procedures for the Formation andCleavage of Steroid Acetals Catalysed by Montmorilloaite K 10

Acetalization of steroid ketones and cleavage of the acetals have ben carried out inexcellent yield under catalysis of montmorillonite K 10.

tRNA cleavage: a new insight

Over the past decades,tRNA was found to be a rich hub of RNA modifications such as 1-methyladenosine and 5-methycytosine modifications and others,holding more than half of all modifications occurring in RNA molecules.Moreover,tRNA was discovered to be a source of various small noncoding RNA species,such as the stress induced angiogenin cleaved tRNA halves(tiRNA)or the miRNA like tRNA derived fragments.tRNA cleavage under stress was fist discovered in bacteria and later was found to be conserved across different species,including mammals.Under cellular stress conditions,tRNA undergoes conformational changes and angiogenin cleaves it into 3′and 5′halves.5′tiRNA halves were shown to repress protein translations.tRNA cleavage is thought of to be a cytoprotective mechanism by which cells evade apoptosis,however some data hints to the opposite;that tiRNA are cytotoxic or at least related to apoptosis initiation.tRNA cleavage also was shown to be affected by tRNA modifications via different enzymes in the cytosol and mitochondria.In this review,we will highlight the biology of tRNA cleavage,show the evidence of it being cytoprotective or a marker of cell death and shed a light on its role in disease models and human diseases as well as possible future directions in this field of RNA research.

PrP^C-related signal transduction is influenced by copper, membrane integrity and the alpha cleavage site

The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human PrPc, mouse PrPc or mouse PrP^C carrying the 3F4 epitope, this study explored the influence of the PrP^C primary sequence on endoproteolytic cleavage and one putative PrPc function, MAP kinase signal transduction, in response to exogenous copper with or without a perturbed membrane environment. PrPc primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat- ed kinase 1/2 （ERK1/2） phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrP^C showed increased N1/C1 cleavage in response to copper alone, accompanied by specific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrP^C-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPc harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPc pri- mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence appears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of PrP^C-related signal transduction in response to exogenous stimuli.

In vitro cleavage of hepatitis B virus C mRNA by 10-23 DNA enzyme

BACKGROUND: 10-23 DNA enzyme is one kind of de-oxyribozymes for RNA cleavage. The inhibition effects of 10-23 DNA enzyme on the expression of the HBV C gene in HepG2. 2. 15 cells were demonstrated previously. The aim of this study was to further explore the cleavage activities of 10-23 DNA enzyme targeting at HBV C gene mRNA in vitro. METHODS: 10-23 DNA enzyme named Drz-HBV-C-9 specific to HBV C gene ORF A1816UG was designed and synthesized. HBV C gene mRNA was obtained by the in vitro transcription method. Cleavage activities of Drz-HBV-C-9 were observed in vitro. Values of kinetic parameters including Km,Kcat and Kcat/Km were calculated accordingly. RESULTS: Under the certain cleavage conditions, Drz-HBV-C-9 could efficiently cleave target mRNA at specific sites in vitro. Cleavage products of 109nt plus 191nt were obtained. The kinetic parameters, Km,Kcat and Kcat/ Km for Drz-HBV-C-9, were 1.4 ×10-9 mol, 1.6 min-1 and 1.1 × 109 mol-1 · min-1, respectively. CONCLUSIONS: 10-23 DNA enzyme targeting at HBV C gene mRNA possesses specific cleavage activities in vitro. This would be a potent antiviral strategy with respect to HBV gene therapy.

Synthesis and Crystal Structure of a Dinuclear Cu(Ⅱ) Complex Based on a Carboxyl-substituted 1H-1,2,3-Triazole and Its DNA Cleavage Activity

The novel dinuclear copper complex [Cu2（H20）2（DMF）2（L）2] （1, H2L = 5-phenyl- 2H-1,2,3-triazole-4-carboxylic acid, DMF = N,N-dimethyl-formamide） has been synthesized and characterized by X-ray single-crystal diffraction. The compound crystallizes in triclinic system, space group P1 with a = 9.591, b = 10.508, c = 15.515A,β = 75.11°, V= 1446.2 A3, Z= 2, Mr = 683.62, Dc = 1.570 g/cm3, μ = 1.531 mm^-1, F（000） = 700, the final R = 0.0404 and wR = 0.1130 for 5327 observed reflections with I 〉 2σ（I）. In each unit of the complex, two Cu2＋ ions coordinated with two triazole ligands to form a dimeric [5,6,5] tricyclic structure. The central Cu atom is five-coordinated, and each copper atom shows a square pyramidal geometry. The crystal structure is stabilized by the inversion-related O-H…O hydrogen bond and C-H…O hydrogen bonding interactions to form a layer structure. Fluorescent spectra show an obvious quenching of fluorescence compared with free 1,2,3-triazole ligand. The results of agarose gel electrophoresis indicate that this complex can cleave the plasmid supercoiled DNA within shorter time in the 50-folds excess of ascorbate under physiological conditions, providing a new example in the research for artificial metal nucleic acid enzyme.

Synthesis, DNA-binding, and Photocleavage of 2,3-Di-2-pyridylquinoxaline-silver(Ⅰ) Complex

A new dinuclear complex, [Ag（L）（CH3CN）]2（ClO4）2·2H2O（L=2,3-di-2-pyridylquinoxaline）, was prepared and characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. The interaction of the complex with calf thymus DNA（CT-DNA） was investigated by absorption, fluorescence spectroscopies, and viscosity measurement. The results suggested that the complex was bound to DNA via an intercalative mode. The intrinsic binding constant value Kb was found to be approximately 1.48×10^3 L·mol^-1. Moreover, the Ag（I） complex could cleave the plasmid pUC19 DNA from the supercoiled Form Ⅰto the nicked FormⅡ under irradiation at 365 nm.

Critical role of cytochrome c1 and its cleavage in porcine reproductive and respiratory syndrome virus nonstructural protein 4-induced cell apoptosis via interaction with nsp4

Porcine reproductive and respiratory syndrome virus.（PRRSV） actively induces cell apoptosis both in vitro and in vivo, which can contribute critically to viral pathogenesis. Previous studies have shown that the PRRSV nonstructural protein 4 （nsp4） is an important mediator of this process, but the underlying molecular details remain poorly understood. In this study, we found that the PRRSV nsp4 interacted with the mitochondrial inner membrane protein cytochrome cl （cyto.cl） and induced its proteolytic cleavage. Interestingly, the cleaved N-terminal fragment of cyto.cl was found to exert apoptotic activity, which could cause mitochondrial fragmentation, resulting in apoptotic cell death. And RNA interference （RNAi） silencing experiments further confirmed the crucial role which cyto.cl played in nsp4- and PRRSV-induced cell apoptosis. Thus, our data provide an important piece of mechanistic clues for PRRSV-induced cell apoptosis and also elucidate a novel mechanism for the 3C-like proteases in this finding.

Synthesis, structure, DNA binding and cleavage activity of a new copper(II) complex of bispyridylpyrrolide

A copper-bispyridylpyrrolide complex [Cu(PDPH)Cl](PDPH = 2,5-bis(2′-pyridyl)pyrrole) was synthesized and characterized. The complex crystallizes in the orthorhombic system with space group Pccn, a = 0.9016(3) nm, b = 1.0931(4) nm, c =2.5319(8) nm, and V = 2.4951(15) nm3. The copper center is situated in a square planar geometry. The interaction of the copper(II)complex with calf thymus DNA(CT-DNA) was investigated by electronic absorption, circular dichroism(CD) and fluorescence spectra. It is proposed that the complex binds to CT-DNA through groove binding mode. Nuclease activity of the complex was also studied by gel electrophoresis method. The complex can efficiently cleave supercoiled p BR322 DNA in the presence of ascorbate(H2A) via oxidative pathway. The preliminary mechanism of DNA cleavage by the complex with different inhibiting reagents indicates that the hydroxyl radicals were involved as the active species in the DNA cleavage process.

Synthesis and Cleavage Activity of Artifical Minic Polypeptides

Two artificial minic polypeptides which are synthetic analogues of natural products with DNA affinity were synthesized, and theirs cleavage activity with DNA were examined. The structures of these compounds was confirmed by ^1H NMR, MS and IR.

Beta-amyloid precursor protein cleavage enzyme-1 expression in adult rat retinal neurons in the early period after lead exposure

Previous studies have reported that non-human primates and rodents exposed to lead during brain development may become dependent on the deposition of pre-determined β-amyloid protein （Aβ）,and exhibit upregulation of β-site amyloid precursor protein expression in old age.However,further evidence is required to elucidate the precise relationship and molecular mechanisms underlying the effects of early lead exposure on excessive Aβ production in adult mammals.The present study investigated the effects of lead exposure on expression of β-amyloid precursor protein cleavage enzyme-1 （BACE-1） in the rat retina and the production of Aβ in early development,using the retina as a window for studying Alzheimer＇s disease.Adult rats were intraocularly injected with different doses of lead acetate （10μmol/L,100μmol/L,1 mmol/L,10 mmol/L and 100 mmol/L）.The results revealed that retinal lead concentration,BACE-1 and its cleavage products β-C-terminal fragment and retina Aβ1-40 were all significantly increased in almost all of the lead exposure groups 48 hours later in a dose-dependent manner.The only exception was the 10μmol/L group.The distribution of BACE-1 in the retina did not exhibit obvious changes,and no distinctive increase in the activation of retinal microglia was apparent.Similarly,retinal synaptophysin expression did not exhibit any clear changes.These data suggest that lead exposure can result in the upregulation of retinal neuron BACE-1 expression in the early period of development and further increase the overproduction of Aβ1-40 in the retina.Our results provided novel insight into the molecular mechanisms underlying environmentally-induced Alzheimer＇s disease.

Acidic Montmorillonite/Cordierite Monolithic Catalysts for Cleavage of Cumene Hydroperoxide

In this work,a series of acidic montmorillonite/cordierite monolithic catalysts were prepared by a coating method using silica sol as the binder.The morphology and structure of the acidic montmorillonite/cordierite samples were characterized by means of X-ray diffraction(XRD),N_2 adsorption/desorption isotherms,and scanning electron microscope(SEM).The cleavage of cumene hydroperoxide(CHP) in a conventional fixed-bed reactor was chosen as a model reaction to evaluate the catalytic activity of the monolithic catalysts.The influences of acidic montmorillonite loading,reaction temperature.CHP concentration,and weight hourly space velocity(WHSV) on the catalytic activity and selectivity of phenol were studied.The results indicated that the obtained acidic montmorillonite/cordierite monolithic catalysts were firm and compact,and the loading of acidic montmorillonite was found to reach 40%(by mass) after three coating operations.The surface area of acidic montmorillonite/cordierite catalysts increases greatly as acidic montmorillonite loading increases due to higher surface area of acidic montmorillonite.Under the optimal reaction conditions(acidic montmorillonite loading of 32.5%(by mass),temperature of 80 ℃,a mass ratio of CHP to acetone of 1:3,and WHSV of CHP of 90 h^(-1)),the conversion of CHP can reach 100%,and the selectivity of phenol is up to 99.8%.

Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

The Effects of Murine Cytomegalovirus on the Maturation, Fertilization, Cleavage and Blastula Formation of Mouse Oocytes In Vitro

To study the effects of mouse cytomegalovirus （MCMV） on the in vitro maturation, fertilization, cleavage and blastula formation of mouse oocytes, the immature oocytes were infected in vitro by MCMVs of different dosages （100 TCID50, 10 TCID50 and 1 TCID50）. The oocytes were then observed for in vitro maturation, fertilization, cleavage and blastula formation and the ultrastructural changes after the culture with the viruses. Our results showed that no significant differences were found in IVM, IVF, cleavage and blastula formation among the groups treated with of virus of various dosages. And ultrastructural abnormality was observed in the oocytes treated by 100 TCID50 of viruses. It is concluded that MCMV did not have any conspicuous effects on IVM, IVF, cleavage and blastula formation of murine immature oocytes.

Helicobacter pylori inhibits the cleavage of TRAF1 via a Cag A-dependent mechanism

AIM To study the impact on cleavage of tumor necrosis factor receptor-associated factor 1(TRAF1) regulated by Helicobacter pylori(H. pylori).METHODS Cleavage of TRAF1 was detected by western blotting in the human gastric cancer cell line AGS following treatment with an apoptosis inducer. Cleavage of TRAF1 mediated by caspase was examined in vitro using specific caspase inhibitors. The effect of the COOH-terminal TRAF1 fragment on gastric cell apoptosis during H. pylori infection was measured using flow cytometry. The impact of H. pylori infection on TRAF1 cleavage was detected in the presence of apoptosis inducer. The roles of H. pylori virulence factors that may regulate TRAF1 cleavage were analyzed using isogenic cag A-, vac A- and cag E- null mutants.RESULTS TRAF1 was found to be cleaved in AGS cells treated with the apoptosis inducer, and caspase-8 was the major caspase involved in the cleavage of TRAF1. The COOH-terminal TRAF1 fragment significantly induced cell apoptosis(P < 0.05) as well as promoted H. pylori-induced cell apoptosis(P < 0.05). H. pylori infection was found to significantly inhibit the cleavage of TRAF1 and to inhibit the activation of caspase-8 in thepresence of the apoptosis inducer at specific infection times and different cell/bacteria ratios. We also found that the effects of cag E- and cag A- null mutants on the inhibition of TRAF1 cleavage and activation of caspase-8 were significantly attenuated, compared with wild-type H. pylori, in the presence of the apoptosis inducer, showing that the virulence factor Cag A was mainly involved in the inhibition of TRAF1 cleavage.CONCLUSION H. pylori infection significantly inhibits the cleavage of TRAF1 via a CagA-dependent mechanism, which would increase the relative amounts of full-length TRAF1 and exert an antiapoptotic effect on H. pylori-infected cells.

Synthesis and DNA cleavage activity of diiron(Ⅲ) complex bearing pyrene group

As DNA cleavage agent, a new diiron（Ⅲ） complex （Fe2Lb）, in which a DNA-intercalator （pyrene） is covalently linked to a diferric moiety, has been synthesized and characterized. The DNA-binding property and DNA cleavage activity of the complex have also been investigated.

Developmental Potential and Clinical Value of Embryos with Abnormal Cleavage Rate

To investigate the developmental potential and clinical value of embryos with abnormal cleavage rate,a retrospective analysis was performed on 66 635 2-prokaryotic(2PN)and 1-pronuclear(1PN)embryos.The embryos were given conventionally in vitro fertilization(IVF)treatment and continuously cultured on the day 3(D3)at the Reproductive Medicine Center,Tongji Medical College,Huazhong University of Science and Technology from January 2016 to December 2017.The embryos were separated into the day-2(D2)undivided group with 106 cases,the arrested development group with 3482 cases,the blastomere reduction group with 541 cases,and the control group with 62 506 cases,respectively.The blastocyst utilization rates of these three abnormal groups were 2.83%,10.86%and 6.84%,respectively,which were significantly different from that in control group(39.46%).Furthermore,2 cases of anabiosis and 1 case of live birth were found in D2 undivided group.In arrested development group,there were 55 cases of anabiosis,11 cases of clinical pregnancy in single-embryo transplantation(including 6 cases of live birth),and 25 cases of clinical pregnancy in combination with one normal embryo transplantation(including 23 cases of live births and 15 cases of dizygotic twins under B-ultrasound).There were 13 case of anabiosis in blastomere reduction group:there was 1 case of single embryo transplantation and clinical pregnancy was obtained;there were also 6 cases of clinical pregnancy in combination with one single normal embryo transplantation(including 5 cases of live births and 2 cases of di2ygotic twins under B-ultrasound).In conclusion,embryos with abnormal cleavage rate still have the potential to continue to develop,and have certain blastocyst utilization rate and live birth.