深入理解化学平衡常数及其应用——对2019年全国理综(Ⅰ卷)化学第28题的分析

在已有的化学平衡常数教学的基础上,提出认知化学平衡常数的新角度--化学平衡常数的多种表达式。依据教材中用浓度表示的化学平衡常数并结合理想气体状态方程,推导用物质的量分数及分压表示的化学平衡常数表达式,分析3者之间的区别和联系,进而应用化学平衡常数的多种表达形式解决2019年全国(Ⅰ卷)化学第28题中的相关问题,使学生深入理解解答这道高考试题的关键所在。同时,拓展了学生对平衡常数的认识,提升了学生灵活应用平衡常数解决问题的能力。     

In situ vaccination and gene-mediated PD-L1 blockade for enhanced tumor immunotherapy

Despite of the promising achievements of immune checkpoints blockade therapy (ICB) in the clinic, which was often limited by low objective responses and severe side effects. Herein, we explored a synergistic strategy to combine in situ vaccination and gene-mediated anti-PD therapy, which was generated by unmethylated cytosine-phosphate-guanine (CpG) and pshPD-L1 gene co-delivery. PEI worked as the delivery carrier to co-deliver the CpG and pshPD-L1 genes, the formed PDC (PEI/DNA/CpG) nanoparticles were further shielded by aldehyde modified polyethylene glycol (OHC-PEG-CHO) via pH responsive Schiff base reaction for OHC-PEG-CHO-PEI/DNA/CpG nanoparticles (P(PDC) NPs) preparation. All steps could be finished within 30 min. Such simple nanoparticles achieved the synergistic antitumor efficacy in B16F10 tumor-bearing mice, and the amplified T cell responses, together with enhanced NK cells infiltration were observed after the combined treatments. In addition, the pH responsive delivery system reduced the side effects triggered by anti-PD therapy. The facile and effective combination strategy we presented here might provide a novel treatment for tumor inhibition.     

Prospects of anionic nanolipoplexes in nanotherapy: transmission electron microscopy and light scattering studies

Currently nanosystems composed of polynucleotides and lipid vesicles (nanolipoplexes) are considered to be promising tools for gene therapeutics. Successful in vivo application of these vectors depends on their physicochemical, technological and biological characteristics including morphology, size distribution, molecular interactions and stability. Anionic nanoliposomes (DPPC:DCP:CHOL) were prepared by two different techniques, namely the conventional thin-film hydration method followed by extrusion, and the heating method (HM), in which no volatile solvent or detergent is used. A non-viral and non-cationic gene transfer vector was constructed by incorporating plasmid DNA (pcDNA3.1/His B/lacZ) to the HM-nanoliposomes by the electrostatic mediation of Ca²⁺ ions. Transfection efficiency of the nanolipoplexes was evaluated using a human bronchial epithelial cell line (16HBE14o-) in the presence of serum. Particle characterisation, stability of the formulations and lipid–DNA interaction studies were performed using transmission electron microscopy (TEM) and light scattering. TEM pictures of nanolipoplexes showed presence of two to four closely packed vesicles with signs of fusion. Efficient delivery of plasmid DNA and subsequent β-galactosidase expression was achieved using the anionic nanolipoplexes. Transfection efficiency increased with lipid:DNA ratio up to 7:1 (w/w), where transfection efficiency was 12-fold higher than in untreated cells. Further increase in lipid ratio decreased transfection. These nanolipoplexes appear to be safe, stable and efficient in the protection and delivery of DNA to different cells and tissues.     

Non‐Heme Dioxygenase Catalyzes Atypical Oxidations of 6,7‐Bicyclic Systems To Form the 6,6‐Quinolone Core of Viridicatin‐Type Fungal Alkaloids

The 6,6‐quinolone scaffold of the viridicatin‐type of fungal alkaloids are found in various quinolone alkaloids which often exhibit useful biological activities. Thus, it is of interest to identify viridicatin‐forming enzymes and understand how such alkaloids are biosynthesized. Here an Aspergillal gene cluster responsible for the biosynthesis of 4′‐methoxyviridicatin was identified. Detailed in vitro studies led to the discovery of the dioxygenase AsqJ which performs two distinct oxidations: first desaturation to form a double bond and then monooxygenation of the double bond to install an epoxide. Interestingly, the epoxidation promotes non‐enzymatic rearrangement of the 6,7‐bicyclic core of 4′‐methoxycyclopenin into the 6,6‐quinolone viridicatin scaffold to yield 4′‐methoxyviridicatin. The finding provides new insight into the biosynthesis of the viridicatin scaffold and suggests dioxygenase as a potential tool for 6,6‐quinolone synthesis by epoxidation of benzodiazepinediones.     

Artificial Splitting of a Non‐Ribosomal Peptide Synthetase by Inserting Natural Docking Domains

The interaction in multisubunit non‐ribosomal peptide synthetases (NRPSs) is mediated by docking domains that ensure the correct subunit‐to‐subunit interaction. We introduced natural docking domains into the three‐module xefoampeptide synthetase (XfpS) to create two to three artificial NRPS XfpS subunits. The enzymatic performance of the split biosynthesis was measured by absolute quantification of the products by HPLC‐ESI‐MS. The connecting role of the docking domains was probed by deleting integral parts of them. The peptide production data was compared to soluble protein amounts of the NRPS using SDS‐PAGE. Reduced peptide synthesis was not a result of reduced soluble NRPS concentration but a consequence of the deletion of vital docking domain parts. Splitting the xefoampeptide biosynthesis polypeptide by introducing docking domains was feasible and resulted in higher amounts of product in one of the two tested split‐module cases compared to the full‐length wild‐type enzyme.     

Superwetting Patterned Membranes with an Anisotropy/Isotropy Transition: Towards Signal Expression and Liquid Permeation

Superwetting membranes with responsive properties have attracted heightened attention because of their fine‐tunable surface wettability. However, their functional diversity is severely limited by the “black‐or‐white” wettability transition. Herein, we describe a coating strategy to fabricate multifunctional responsive superwetting membranes with SiO₂/octadecylamine patterns. The adjustable patterns in the responsive region are the key factor for functional diversity. Specifically, the coated part of the membrane displayed a superhydrophobicity/superhydrophilicity transition at different pH values, whereas the uncoated part exhibited invariant superhydrophilicity. On the basis of this anisotropy/isotropy transition, the membranes can serve as either responsive permeable membranes or signal‐expression membranes, thus enabling the responsive separation and permeation of liquids with satisfactory separation efficiency (>99.90 %) and flux (ca. 60 L m^?2 h), as well as real‐time liquid signal expression with alterable signals.     

Prokaryotic Expression and Polyclonal Antibody Preparation of PRL3

Phosphatase of regenerating liver 3(PRL3),which belongs to the superfamily of protein tyrosine phosphatases(PTPs),represents a group of low molecular weight PTPs that participate in tumorigenesis and metastasis processes.Presented here are the results of cloning,prokaryotic expression,purification,and polyclonal antibody preparation of PRL3.To obtain a specific polyclonal antibody against PRL3,the authors have prepared GST-PRL3 to immunize rabbits and purify an anti-PRL3 polyclonal antibody by negative selection affinity columns.Western blot analysis shows that the anti-PRL3 polyclonal antibody has a specific binding ability with PRL3 protein.The anti-PRL3 polyclonal antibody provides a good tool to further study the function of PRL3.     

Caseinolytic Proteins (Clp) in the Genus Klebsiella: Special Focus on ClpK

Caseinolytic proteins (Clp), which are present in both prokaryotes and eukaryotes, play a major role in cell protein quality control and survival of bacteria in harsh environmental conditions. Recently, a member of this protein family, ClpK was identified in a pathogenic strain of Klebsiella pneumoniae which was responsible for nosocomial infections. ClpK is linked to the thermal stress survival of this pathogen. The genome wide analysis of Clp proteins in Klebsiella spp. indicates that ClpK is present in only 34% of the investigated strains. This suggests that the uptake of the clpk gene is selective and may only be taken up by a pathogen that needs to survive harsh environmental conditions. In silico analyses and molecular dynamic simulations show that ClpK is mainly α-helical and is highly dynamic. ClpK was successfully expressed and purified to homogeneity using affinity and anion exchange chromatography. Biophysical characterization of ClpK showed that it is predominantly alpha-helical, and this is in agreement with in silico analysis of the protein structure. Furthermore, the purified protein is biologically active and hydrolyses ATP in a concentration- dependent manner.     

Seed priming with cold plasma improved seedling performance,secondary metabolism,and expression of deacetylvindoline O-acetyltransferase gene in Catharanthus roseus

The plasma-primed seeds of Catharanthus roseus were cultured in a hormone-free culture medium under sterile conditions. Plasma of 30 or 60 s improved root length (mean = 41.4%) and biomass (mean = 47%), whereas plasma of 90 s delayed plant growth. The plasma treatments enhanced concentrations of photosynthetic pigments and soluble phenols. Plasma of 90 s increased the proline level. With a similar trend, plasma priming induced activities of phenylalanine ammonia-lyase, catalase (about twofold) and peroxidase (31%) enzymes. Plasma also upregulated the expressions of deacetylvindoline O-acetyltransferase gene by an average of 7.8 times. Similarly, the plasma-treated seedlings contained higher concentrations of alkaloids (mean = 72%). Here, molecular evidence is provided on the plasma-associated modifications in secondary metabolism.