Physicochemical properties and antibacterial mechanism of theabrownins prepared from different catechins catalyzed by polyphenol oxidase and peroxidase

Theabrownins(TBs)are the characteristic functional and quality components of dark teas such as Pu’er tea and Chin-brick tea.TBs are a class of water-soluble brown polymers with multi-molecular weight distribution produced by the oxidative polymerisation of tea polyphenols during the fermentation process of dark tea,both enzymatically and non-enzymatically.TBs have been extracted and purified from dark tea all the time,but the obtained TBs contain heterogeneous components such as polysaccharides and caffeine in the bound state,which are difficult to remove.The isolation and purification process was tedious and required the use of organic solvents,which made it difficult to industrialise TBs.In this study,epigallocatechin(EGC),epigallocatechin gallate(EGCG),epigallocatechin gallate(ECG),EGC/EGCG(mass ratio 1:1),EGCG/ECG(mass ratio 1:1),EGC/ECG(mass ratio 1:1)and EGC/EGCG/ECG(mass ratio 1:1:1)as substrates and catalyzed by polyphenol oxidase(PPO)and peroxidase(POD)in turn to produce TBs,named TBs-dE-1,TBs-dE-2,TBs-dE-3,TBs-dE-4,TBs-dE-5,TBs-dE-6 and TBs-dE-7.The physicochemical properties and the antibacterial activity and mechanism of TBs-dE-1–7 were investigated.Sensory and colour difference measurements showed that all seven tea browning samples showed varying degrees of brownish hue.Zeta potential in aqueous solutions at pH 3.0–9.0 indicated that TBs-dE-1–7 was negatively charged and the potential increased with increasing pH.The characteristic absorption peaks of TBs-dE-1–7 were observed at 208 and 274 nm by UV-visible(UV-vis)scanning spectroscopy.Fourier transform infrared(FT-IR)spectra indicated that they were phenolic compounds.TBs-dE-1–7 showed significant inhibition of Escherichia coli DH5α(E.coli DH5α).TBs-dE-3 showed the strongest inhibitory effect with minimum inhibitory concentration(MIC)of 1.25 mg mL–1 and MBC of 10 mg mL–1,followed by TBs-dE-5 and TBs-dE-6.These three TBs-dEs were selected to further investigate their inhibition mechanism.The TBs-dE was found to damage the extracellular membrane of E.coli DH5α,causing leakage of contents,and increase intracellular reactive oxygen content,resulting in abnormal cell metabolism due to oxidative stress.The results of the study provide a theoretical basis for the industrial preparation and product development of TBs.

The role of sound stimulation in production of plant secondary metabolites

Sound vibration is one of natural stimuli trigging physiological changes in plants.Recent studies showed that sound waves stimulated production of a variety of plant secondary metabolites,including flavonoids,in order to enhance seed germination,flowering,growth or defense.In this review,we examine the potential role of sound stimulation on the biosynthesis of secondary metabolites and the followed cascade of physiological changes in plants,from the perspective of transcriptional regulation and epigenetic regulation for the first time.A systematic summary showed that a wide range of factors may regulate the production of secondary metabolites,including plant species,growth stage,sound types,sound frequency,sound intensity level and exposure time,etc.Biochemical and physiological changes due to sound stimulation were thoroughly summarized as well,for secondary metabolites can also act as a free radical scavenger,or a hormone signaling molecule.We also discussed the limits of previous studies,and the future application of sound waves in biosynthesis of plant secondary metabolites.

Lindqvist-type Polyoxometalates Act as Anti-breast Cancer Drugs via Mitophagy-induced Apoptosis

Objective Lindqvist-type polyoxometalates(POMs)exhibit potential antitumor activities.This study aimed to examine the effects of Lindqvist-type POMs against breast cancer and the underlying mechanism.Methods Using different cancer cell lines,the present study evaluated the antitumor activities of POM analogues that were modified at the body skeleton based on molybdenum-vanadium-centered negative oxygen ion polycondensations with different side strains.Cell colony formation assay,autophagy detection,mitochondrial observation,qRT-PCR,Western blotting,and animal model were used to evaluate the antitumor activities of POMs against breast cancer cells and the related mechanism.Results MO-4,a Lindqvist-type POM linking a proline at its side strain,was selected for subsequent experiments due to its low half maximal inhibitory concentration in the inhibition of proliferation of breast cancer cells.It was found that MO-4 induced the apoptosis of multiple types of breast cancer cells.Mechanistically,MO-4 activated intracellular mitophagy by elevating mitochondrial reactive oxygen species(ROS)levels and resulting in apoptosis.In vivo,breast tumor growth and distant metastasis were significantly reduced following MO-4 treatment.Conclusion Collectively,the results of the present study demonstrated that the novel Lindqvist-type POM MO-4 may exhibit potential in the treatment of breast cancer.

Synthesis and Characterization of Carboxyl-terminated Polyethylene Glycol Functionalized Mesoporous Silica Nanoparticles

Colloidal mesoporous silica nanoparticles functionalized with carboxy-terminated polyethylene glycol(CMS-PEG-COOH) were successfully synthesized by covalently grafting dicarboxy-terminated polyethylene glycol(HOOC-PEG-COOH) on the surface of the amino functionalized CMS nanoparticles with amide bond as a cross linker. Moreover, the structural and particle properties of CMS-PEG-COOH were characterized by nuclear magnetic resonance spectroscopy(1 H-NMR), transmission electron microscopy(TEM), dynamic light scattering(DLS), nitrogen adsorption-desorption measurements, X-ray diffraction(XRD), and Fourier transform infrared spectroscopy(FT-IR). The nanomaterials presented a relatively uniform spherical shape morphology with diameters of about 120 nm,and favorable dispersibility in weak acid solution. The CMSPEG-COOH exhibited no changes in the state of amorphous, while the mesopores sizes of 5.25 nm might provide the nanomaterials with large capacity for the loading and releasing of drugs. So the results indicated that CMSPEG-COOH might be a critical nanomaterial for drug delivery system in the future.

Carbonaceous Nanofibers-titanium Dioxide Nanocomposites: Synthesis and Use as a Platform for Removal of Dye Pollutants

A mild chemistry route was developed to prepare carbonaceous nanofibers-titanium dioxide(CNF-TiO_2) nanocomposites for removal of dye pollutants. In the process of the template-directed hydrothermal carbonization(HTC), ultrathin Te nanowires were adopted as templates and glucose as the carbon source, and TiO_2 was decorated on CNF via the hydrolysis of tetrabutyltitanate in the presence of CNF in ethanol. The as-prepared materials were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy-dispersive X-ray(EDX) and X-ray diffraction(XRD). SEM and TEM observations displayed that TiO_2 nanoparticles were anchored on the CNF. EDX and XRD data confirmed that the assynthesized samples were CNF-TiO_2, and TiO_2 belonged to anatase titania. Taking advantage of combined benefits of carbonaceous nanofibers and titanium dioxide, these CNF-TiO_2 nanocomposites exhibited higher removal efficiency in a short time and showed good reusability. It was showed that over 97% of Rhodamine B could be removed in 15 min without generating the solid and liquid wastes. The removal efficiency of dyes was still over 80% after reuse in five cycles. All the results demonstrate that the as-prepared CNF-TiO_2 composites are effective materials for fast and effective removal of dye pollutants and thus can provide a new platform for dye decontamination.

Preparation and Characterization of Carboxyl Functionalized Fluorescent Mesoporous Silica Nanoparticles Containing 8-Hydroxyquinolinate Zinc Complexes

Fluorescent mesoporous silica nanoparticles functionalized with carboxyl group(Znq-CMSCOOH) were successfully synthesized by in situ formation route of 8-hydroxyquinolinate zinc complexes in channels of mesoporous silica nanoparticles and post-grafting of carboxyl group on the surface. Moreover,the particle size and structural properties of Znq-CMS-COOH were characterized by transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FT-IR),UV-vis spectrometer, fluorescence spectrometer and nitrogen adsorption-desorption measurements. The obtained results suggest that the Znq-CMS-COOH presents the uniform spherical shape with the mean diameter of about 85 nm and the obvious wormhole arrangement mesoporous. In addition, the Znq-CMS-COOH possesses green fluorescence with the emission peaks at 495 nm. So the Znq-CMS-COOH, which is beneficial to further modification and tracing, might be a great potential carrier for applying in drug delivery system in the future.

The First Isolation of a Cyanophage-Synechococcus System from the East China Sea

A cyanophage strain and its host Synechococcus were isolated from the East China Sea. The host Synechococcus sp. S J01 was characterized by its 16S rRNA, ITS, andpsbA gene sequences as well as by its morphological appearance and pigmentation. The cyanophage, strain S-SJ2, was able to cause a lytic infection of the coastal Synechococcus. TEM of negative-stained specimens showed that the phage isolate has an isometric head with a diameter of 68 nm and a long tail with a length of 280 nm. The cyanophage-Synechococcus system from the East China Sea shares many properties with other marine cyanophage-Synechocoecus systems worldwide.

Fe_3O_4@PAM@NTA-Ni^(2+) Magnetic Composite Nanoparticles for Highly Specific Separation of His-tagged Proteins

A facile approach has been developed to synthesize Fe3O4@PAM（polyacrylamide） nanoparticles（NPs） with carboxyl groups on the surfaces by copolymerization with acrylamide and acrylic acid in Fe3O4 NPs aqueous suspension. Nitrilotriacetic acid（NTA） was conjugated to the magnetic NPs via well-known carboniimide chemistry using EDC and NHS. The Ni^（2＋） ions loaded on the surface of NPs provide abundant docking sites for immobilization of His-tagged green fluorescent proteins（His-tagged GFP）. The high magnetic property of Fe3O4@PAM@NTA-Ni^（2＋） allows an easy separation of the NPs from solution under an external magnetic field, with high His-tagged protein binding capacity（42 μg protein/mg of NPs）. The NPs can be recycled for at least four times without significant loss of binding capacity to proteins. These materials show great potential to separate His-tagged protein with low-cost purification at industrial scale.

Tumor-targeted self-assembled micelles reducing PD-L1 expression combined with ICIs to enhance chemo-immunotherapy of TNBC

Immune checkpoint inhibitors(ICIs)therapy targeting programmed cell death ligand 1(PD-L1)and programmed death protein 1(PD-1)had exhibited significant clinical benefits for cancer treatment such as triple negative breast cancer(TNBC).However,the relatively low anti-tumor immune response rate and ICIs drug resistance highlight the necessity of developing ICIs combination therapy strategies to improve the anti-tumor effect of immunotherapy.Herein,the immunomodulator epigallocatechin gallate palmitate(PEGCG)and the immunoadjuvant metformin(MET)self-assembled into tumor-targeted micelles via hydrogen bond and electrostatic interaction,which encapsulated the therapeutic agents doxorubicin(DOX)-loaded PEGCG-MET micelles(PMD)and combined with ICIs(anti-PD-1 antibody)as therapeutic strategy to reduce the endogenous expression of PD-L1 and improve the tumor immunosuppressive microenvironment.The results presented that PMD integrated chemotherapy and immunotherapy to enhance antitumor efficacy in vitro and in vivo,compared with DOX or anti-PD-1 antibody for the therapy of TNBC.PMD micelles might be a potential candidate,which could remedy the shortcomings of antibody-based ICIs and provide synergistic effect to enhance the antitumor effects of ICIs in tumor therapy.

Integration of advanced biotechnology for green carbon

Carbon neutralization has been introduced as a long-term policy to control global warming and climate change.As plant photosynthesis produces the most abundant lignocellulosic biomass on Earth,its conversion to biofuels and bioproducts is considered a promising solution for reducing the net carbon release.However,natural lignocellulose recalcitrance crucially results in a costly biomass process along with secondary waste liberation.By updating recent advances in plant biotechnology,biomass engineering,and carbon nanotechnology,this study proposes a novel strategy that integrates the genetic engineering of bioenergy crops with green-like biomass processing for cost-effective biofuel conversion and high-value bioproduction.By selecting key genes and appropriate genetic manipulation approaches for precise lignocellulose modification,this study highlights the desirable genetic site mutants and transgenic lines that are raised in amorphous regions and inner broken chains account for high-density/length-reduced cellulose nanofiber assembly in situ.Since the amorphous regions and inner-broken chains of lignocellulose substrates are defined as the initial breakpoints for enhancing biochemical,chemical,and thermochemical conversions,desirable cellulose nanofibers can be employed to achieve nearcomplete biomass enzymatic saccharification for maximizing biofuels or high-quality biomaterials,even under cost-effective and green-like biomass processes in vitro.This study emphasizes the optimal thermal conversion for generating high-performance nanocarbons by combining appropriate nanomaterials generated from diverse lignocellulose resources.Therefore,this study provides a perspective on the potential of green carbon productivity as a part of the fourth industrial revolution.

Thermostable ethanol tolerant xylanase from a cold-adapted marine species Acinetobacter johnsonii

A xylanase-producing bacterium, isolated from deep sea sediments, was identified as the cold-adapted marine species Acinetobacter Johnsonii. A cold-adapted marine species Acinetobacter Johnsonii could grow at 4 ℃. The optimum temperature and pH of xylanase from a cold-adapted marine species Acinetobacter Johnsonii were 55 ℃ and pH 6.0. Xylanase from a cold-adapted marine species Acinetobacter Johnsonii remained at 80% activity after incubation for 1 h at 65 ℃. The xylanase activity was 1.2-fold higher in 4% ethanol solution than in ethanol free solution. Gibbs free energy of denaturation, ΔG, was higher in 4% ethanol solution than in ethanol free solution. Thermostable ethanol tolerant xylanase was valuable for bioethanol production by simultaneous saccharification and fermentation process with xylan as a carbon source.

A cold adapt and ethanol tolerant endoglucanase from a marine Bacillus subtilis

The catalytic properties and thermodynamic kinetics of the endoglucanase from a marine Bacillus subtilis were analyzed. Optimum pH and temperature of the endoglucanase activity were 5.0 and 35 °C. The endoglucanase activity, melt point temperature was 1.13 folds(247.02 U·ml^(-1)), 2.1 °C higher(39.2 °C) in 6% ethanol solution than that(218.60 U·ml^(-1)),(37.1 °C) in free ethanol. At 40 °C–55 °C, Gibbs free energy, ΔG, and the content ofα-helix was higher in 6% ethanol solution than that in ethanol free solution. The increasing of α-helix content led to higher activity and better thermostability in ethanol solution. The cold adapt ethanol tolerant endoglucanase was valuable for bioethanol product by simultaneous saccharification and fermentation process.

Ribonucleotide reductase M2 (RRM2): Regulation, function and targeting strategy in human cancer

Ribonucleotide reductase M2(RRM2)is a small subunit in ribonucleotide reduc-tases,which participate in nucleotide metabolism and catalyze the conversion of nucleotides to deoxynucleotides,maintaining the dNTP pools for DNA biosynthesis,repair,and replication.RRM2 performs a critical role in the malignant biological behaviors of cancers.The structure,regulation,and function of RRM2 and its inhibitors were discussed.RRM2 gene can produce two transcripts encoding the same ORF.RRM2 expression is regulated at multiple levels during the processes from transcription to translation.Moreover,this gene is associated with resistance,regulated cell death,and tumor immunity.In order to develop and design inhibitors of RRM2,appropriate strategies can be adopted based on different mechanisms.Thus,a greater appreciation of the characteristics of RRM2 is a benefit for understanding tumorigenesis,resistance in cancer,and tumor microenvironment.Moreover,RRM2-targeted therapy will be more attention in future therapeutic approaches for enhancement of treatment effects and amelioration of the dismal prognosis.

Recent advances in the study of hepatitis B virus covalently closed circular DNA

Chronic hepatitis B infection is caused by hepatitis B virus(HBV) and a total cure is yet to be achieved. The viral covalently closed circular DNA(ccc DNA) is the key to establish a persistent infection within hepatocytes. Current antiviral strategies have no effect on the pre-existing ccc DNA reservoir. Therefore, the study of the molecular mechanism of ccc DNA formation is becoming a major focus of HBV research. This review summarizes the current advances in ccc DNA molecular biology and the latest studies on the elimination or inactivation of ccc DNA, including three major areas:(1) epigenetic regulation of ccc DNA by HBV X protein,(2) immune-mediated degradation,and(3) genome-editing nucleases. All these aspects provide clues on how to finally attain a cure for chronic hepatitis B infection.

B-lymphoid tyrosine kinase-mediated FAM83A phosphorylation elevates pancreatic tumorigenesis through interacting with β-catenin

Abnormal activation of Wnt/β-catenin-mediated transcription is closely associated with the malignancy of pancreatic cancer.Family with sequence similarity 83 member A(FAM83A)was shown recently to have oncogenic effects in a variety of cancer types,but the biological roles and molecular mechanisms of FAM83A in pancreatic cancer need further investigation.Here,we newly discovered that FAM83A binds directly toβ-catenin and inhibits the assembly of the cytoplasmic destruction complex thus inhibiting the subsequent phosphorylation and degradation.FAM83A is mainly phosphorylated by the SRC non-receptor kinase family member BLK(B-lymphoid tyrosine kinase)at tyrosine 138 residue within the DUF1669 domain that mediates the FAM83A-β-catenin interaction.Moreover,FAM83A tyrosine 138 phosphorylation enhances oncogenic Wnt/β-catenin-mediated transcription through promotingβ-catenin-TCF4 interaction and showed an elevated nucleus translocation,which inhibits the recruitment of histone deacetylases by TCF4.We also showed that FAM83A is a direct downstream target of Wnt/β-catenin signaling and correlates with the levels of Wnt target genes in human clinical pancreatic cancer tissues.Notably,the inhibitory peptides that target the FAM83A-β-catenin interaction significantly suppressed pancreatic cancer growth and metastasis in vitro and in vivo.Our results revealed that blocking the FAM83A cascade signaling defines a therapeutic target in human pancreatic cancer.

Engineered geranyl diphosphate methyltransferase produces 2-methyl-dimethylallyl diphosphate as a noncanonical C_(6) unit for terpenoid biosynthesis

Terpenoids constitute the largest class of natural products with complex structures,essential functions,and versatile applications.Creation of new building blocks beyond the conventional five-carbon(C_(5))units,dimethylallyl diphosphate(DMAPP)and isopentenyl diphosphate,expands significantly the chemical space of terpenoids.Structure-guided engineering of an S-adenosylmethionine-dependent geranyl diphosphate(GPP)C2-methyltransferase from Streptomyces coelicolor yielded variants converting DMAPP to a new C_(6) unit,2-methyl-DMAPP.Mutation of the Gly residue at the position 202 resulted in a smaller substrate-binding pocket to fit DMAPP instead of its native substrate GPP.Replacement of Phe residue at the position 222 with a Tyr residue contributed to DMAPP binding via hydrogen bond.Furthermore,using Escherichia coli as the chassis,we demonstrated that 2-methyl-DMAPP was accepted as a start unit to generate noncanonical trans-and cis-prenyl diphosphates(C_(5n+1))and terpenoids.This work provides insights into substrate recognition of prenyl diphosphate methyltransferases,and strategies to diversify terpenoids by expanding the building block portfolio.

Integrated pathway engineering and transcriptome analysis for improved astaxanthin biosynthesis in Yarrowia lipolytica

Astaxanthin is a high value carotenoid with a broad range of commercial applications due to its superior antioxidant properties.In this study,β-carotene-producing Yarrowia lipolytica XK17 constructed in the lab was employed for astaxanthin biosynthesis.The catalytic effects ofβ-carotene ketolase CrtW andβ-carotene hydroxylase CrtZ from various species were investigated.The PspCrtW from Paracoccus sp.and HpCrtZ^(#) from Haematococcus pluvialis were confirmed to be the best combination in convertingβ-carotene.Several key bottlenecks in biomass and astaxanthin biosynthesis were effectively eliminated by optimizing the expression of the above enzymes and restoring uracil/leucine biosynthesis.In addition,the effects of astaxanthin biosynthesis on cell metabolism were investigated by integrated analysis of pathway modification and transcriptome information.After further optimization,strain DN30 was able to synthesize up to 730.3 mg/L astaxanthin in laboratory 5-L fermenter.This study provides a good metabolic strategy and a sustainable development platform for high-value carotenoid production.