In this paper, after analyzing the structural system of the digital resource sharing model in colleges and universities, a shared storage model based on cloud storage is designed, and a digital ...teaching resource management and sharing platform for colleges and universities based on cloud storage is constructed on this basis. In order to realize accurate sharing, the sharing behaviors of teaching resources are symbolically illustrated, double behavior aggregation is performed, and a multidimensional preference personalized recommendation algorithm, i.e., DB-CGAT model, is designed to construct the personalized sharing module of teaching resources that integrates the behavioral graph. In addition, three types of experiments are conducted on the personalized sharing module of the platform to test its sharing performance and overall performance. The results show that the accuracy of this model is reduced by 0.04 compared with the traditional algorithm; the 90 percent time of login transaction is 2.44, and the time of query transaction is 1.46, which is all up to the standard value. All the action actions are green, and the number of clicks and throughputs in 5~30ss are around 120. Universities can benefit from the digital teaching resource management and sharing platform designed in this paper, which can improve teaching efficiency.
Enzymes are increasingly explored for use in asymmetric synthesis
, but their applications are generally limited by the reactions available to naturally occurring enzymes. Recently, interest in ...photocatalysis
has spurred the discovery of novel reactivity from known enzymes
. However, so far photoinduced enzymatic catalysis
has not been used for the cross-coupling of two molecules. For example, the intermolecular coupling of alkenes with α-halo carbonyl compounds through a visible-light-induced radical hydroalkylation, which could provide access to important γ-chiral carbonyl compounds, has not yet been achieved by enzymes. The major challenges are the inherent poor photoreactivity of enzymes and the difficulty in achieving stereochemical control of the remote prochiral radical intermediate
. Here we report a visible-light-induced intermolecular radical hydroalkylation of terminal alkenes that does not occur naturally, catalysed by an 'ene' reductase using readily available α-halo carbonyl compounds as reactants. This method provides an efficient approach to the synthesis of various carbonyl compounds bearing a γ-stereocentre with excellent yields and enantioselectivities (up to 99 per cent yield with 99 per cent enantiomeric excess), which otherwise are difficult to access using chemocatalysis. Mechanistic studies suggest that the formation of the complex of the substrates (α-halo carbonyl compounds) and the 'ene' reductase triggers the enantioselective photoinduced radical reaction. Our work further expands the reactivity repertoire of biocatalytic, synthetically useful asymmetric transformations by the merger of photocatalysis and enzyme catalysis.
•Morin reversibly inhibits tyrosinase activity in a competitive manner.•Morin binds to tyrosinase mainly by hydrogen bonds and van der Waals forces.•Morin interacts with several residues located ...within the active pocket of tyrosinase.•The binding of morin to tyrosinase induces conformational changes of the enzyme.
Tyrosinase is a key enzyme in the production of melanin in the human body, excessive accumulation of melanin can lead to skin disorders. Morin is an important bioactive flavonoid compound widely distributed in plants and foods of plant origin. In this study, the inhibitory kinetics of morin on tyrosinase and their binding mechanism were determined using spectroscopic and molecular docking techniques. The results indicate that morin reversibly inhibited tyrosinase in a competitive manner through a multi-phase kinetic process. Morin was found to bind to tyrosinase at a single binding site mainly by hydrogen bonds and van der Waals forces. Analysis of circular dichroism spectra revealed that the binding of morin to tyrosinase induced rearrangement and conformational changes of the enzyme. Moreover, molecular docking results suggested that morin competitively bound to the active site of tyrosinase with the substrate levodopa.
Directed evolution aims to expedite the natural evolution process of biological molecules and systems in a test tube through iterative rounds of gene diversifications and library screening/selection. ...It has become one of the most powerful and widespread tools for engineering improved or novel functions in proteins, metabolic pathways, and even whole genomes. This review describes the commonly used gene diversification strategies, screening/selection methods, and recently developed continuous evolution strategies for directed evolution. Moreover, we highlight some representative applications of directed evolution in engineering nucleic acids, proteins, pathways, genetic circuits, viruses, and whole cells. Finally, we discuss the challenges and future perspectives in directed evolution.
Efficient acetaminophen (APAP) degradation in the natural pyrite/peroxymonosulfate (PMS) system under acidic conditions was observed. Approximately 88.8% of APAP degradation was attributed to sulfate ...radical and the remaining 11.2% of APAP degradation was attributed to singlet oxygen. Sequential experiments and XPS analysis showed that the rapid Fe(III)/Fe(II) cycle was attributed to the sulfur species at the surface of pyrite. Pyrite showed an excellent stability and reusability, which was successfully applied to long-term APAP removal. This study provides a new understanding of the mechanism in pyrite/PMS system and suggests a simply operative and cost-effective method to treat organic contaminants.
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•Acetaminophen is efficiently degraded in pyrite/PMS system under acidic conditions.•Sulfate radical was identified as the dominant oxidant for acetaminophen degradation.•Sequential activation of PMS by pyrite allowed long-term removal of acetaminophen.
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•Intestinal oxidative stress depends on the balance of ROS.•The antioxidant defense system protects intestine from oxidative stress damage.•Phytochemicals with health effects could be ...developed to nutritional supplements.
Oxidative stress occurs when there exists an imbalance between the generation and elimination of reactive oxygen species (ROS). As inevitable exposure to foreign substances and microbial pathogens, intestine is a key resource of ROS. Disproportionate generation and long-term exposure to ROS lead to various intestinal diseases, such as inflammatory bowel diseases (IBD), enteric infections, ischemic intestinal injury and colorectal cancers. Natural nutrients including vitamins, proteins, fats, minerals and phytochemicals provide numerous evidences that they can protect the health of intestine and alleviate the damage caused by oxidative stress, which can be developed as novel functional foods. This review summarized the recent research progress on the insights of the causes, mechanisms of intestinal oxidative stress and the health intervention effects of nutrients. This review has also given the prospects that the new discovered nutrients with health benefits might be developed as novel functional foods or possible nutraceutical agents.
Actinobacteria, particularly those of genus Streptomyces, remain invaluable hosts for the discovery and engineering of natural products and their cognate biosynthetic pathways. However, genetic ...manipulation of these bacteria is often labor and time intensive. Here, we present an engineered CRISPR/Cas system for rapid multiplex genome editing of Streptomyces strains, demonstrating targeted chromosomal deletions in three different Streptomyces species and of various sizes (ranging from 20 bp to 30 kb) with efficiency ranging from 70 to 100%. The designed pCRISPomyces plasmids are amenable to assembly of spacers and editing templates via Golden Gate assembly and isothermal assembly (or traditional digestion/ligation), respectively, allowing rapid plasmid construction to target any genomic locus of interest. As such, the pCRISPomyces system represents a powerful new tool for genome editing in Streptomyces.
Long noncoding RNAs (lncRNAs) play crucial roles in tumor progression and are aberrantly expressed in various cancers. However, the functional roles of lncRNAs in breast cancer remain largely ...unknown.
Based on public databases and integrating bioinformatics analyses, the overexpression of lncRNA BCRT1 in breast cancer tissues was detected and further validated in a cohort of breast cancer tissues. The effects of lncRNA BCRT1 on proliferation, migration, invasion and macrophage polarization were determined by in vitro and in vivo experiments. Luciferase reporter assay and RNA immunoprecipitation (RIP) were carried out to reveal the interaction between lncRNA BCRT1, miR-1303, and PTBP3. Chromatin immunoprecipitation (ChIP) and RT-PCR were used to evaluate the regulatory effect of hypoxia-inducible factor-1α (HIF-1α) on lncRNA BCRT1.
LncRNA BCRT1 was significantly upregulated in breast cancer tissues, which was correlated with poor prognosis in breast cancer patients. LncRNA BCRT1 knockdown remarkably suppressed tumor growth and metastasis in vitro and in vivo. Mechanistically, lncRNA BCRT1 could competitively bind with miR-1303 to prevent the degradation of its target gene PTBP3, which acts as a tumor-promoter in breast cancer. LncRNA BCRT1 overexpression could promote M2 polarization of macrophages, mediated by exosomes, which further accelerated breast cancer progression. Furthermore, lncRNA BCRT1 was upregulated in response to hypoxia, which was attributed to the binding of HIF-1α to HREs in the lncRNA BCRT1 promoter.
Collectively, these results reveal a novel HIF-1α/lncRNA BCRT1/miR-1303/PTBP3 pathway for breast cancer progression and suggest that lncRNA BCRT1 might be a potential biomarker and therapeutic target for breast cancer.
Objective
To evaluate the role of bioimpedance-defined overhydration (BI-OH) parameters in predicting the risk of mortality and cardiovascular (CV) events in patients undergoing dialysis.
Methods
We ...searched multiple electronic databases for studies investigating BI-OH indicators in the prediction of mortality and CV events through 23 May 2020. We assessed the effect of BI-OH indexes using unadjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Sensitivity analysis was used for each outcome.
Results
We included 55 studies with 104,758 patients in the meta-analysis. Extracellular water/total body water (ECW/TBW) >0.4 (HR 5.912, 95% CI: 2.016–17.342), ECW/intracellular water (ICW) for every 0.01 increase (HR 1.041, 95% CI: 1.031–1.051), and OH/ECW >15% (HR 2.722, 95% CI: 2.005–3.439) increased the risk of mortality in patients receiving dialysis. ECW/TBW >0.4 (HR 2.679, 95% CI: 1.345–5.339) and ECW/ICW per increment of 10% (HR 1.032, 95% CI: 1.017–1.047) were associated with an increased risk of CV events in patients undergoing dialysis. A 1-degree increase in phase angle was a protective factor for both mortality (HR 0.676, 95% CI: 0.474–0.879) and CV events (HR 0.736, 95% CI: 0.589–0.920).
Conclusions
BI-OH parameters might be independent predictors for mortality and CV events in patients undergoing dialysis.
Covering up to end 2015Microbial fermentation provides an attractive alternative to chemical synthesis for the production of structurally complex natural products. In most cases, however, production ...titers are low and need to be improved for compound characterization and/or commercial production. Owing to advances in functional genomics and genetic engineering technologies, microbial hosts can be engineered to overproduce a desired natural product, greatly accelerating the traditionally time-consuming strain improvement process. This review covers recent developments and challenges in the engineering of native and heterologous microbial hosts for the production of bacterial natural products, focusing on the genetic tools and strategies for strain improvement. Special emphasis is placed on bioactive secondary metabolites from actinomycetes. The considerations for the choice of host systems will also be discussed in this review.
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