Covering: up to 2016Antimycin-type depsipeptides are a family of natural products with great structural diversity and outstanding biological activities. These compounds have typically been isolated ...from actinomycetes and are generated from hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) assembly lines. This review covers the literature on the four classes of antimycin-type depsipeptides, which differ by macrolactone ring size, and it discusses the discovery, biosynthesis, chemical synthesis, and biological activities of this family of compounds.
The evaluation of the elastic modulus of recycled concrete is one of the focuses of civil engineering and structural engineering, which is not only related to the stability of building structures but ...also related to the resource utilization of concrete. Therefore, based on the IRSM method in mesoscale, a novel model for predicting the elastic modulus of recycled concrete is proposed which has the advantages of being low-cost and high-precision, amongst others, compared to theoretical and experimental methods. Then, the influence of coarse aggregate, contact surface, gelling material, and air bubbles on the elastic modulus of recycled concrete is studied. The IRSM model includes four processes: Identification, Reconstruction, Simulation, and Monte Carlo, which can accurately reconstruct the geometric characteristics of coarse aggregate, efficiently reconstruct the coarse aggregate accumulation model, and quickly analyze the elastic modulus of concrete, as well as fully consider the nonuniform characteristics of coarse aggregate distribution and shape. Compared with the experimental results, the error is less than 5%, which verifies the rationality of the IRSM method. The results of the parametric analysis show that the influence of each factor on the elastic modulus of concrete in descending order is elastic modulus of cement, elastic modulus of coarse aggregate, content of coarse aggregate, content of air voids, elastic modulus of contacting surface, and thickness of contacting surface, and the corresponding Pearson's Coefficients are 0.688, 0.427, 0.412, -0.269, 0.188, and -0.061, respectively, in which the content of air voids and thickness of contact surface have a negative effect on the elastic modulus of concrete. These influences mainly affect the deformation resistance (elastic modulus) of concrete through "force chain" adjustment, including the force transfer effect, number of paths, and integrity.
Advances in nano-lubricant additives are vital to the pursuit of energy efficiency and sustainable development. Carbon dots (CDs) have been widely investigated in the domain of lubricant additives ...owing to their extraordinary tribological properties, in particular, their friction-reducing and anti-wear properties. Metal-doped CDs are a new type of CDs, and their friction-reducing and anti-wear properties are attracting increasing attention. Therefore, a series of CDs doped with various divalent metal ions have been successfully synthesized via one-pot pyrolysis. The tribological properties of the synthesized CDs as water-based lubricant additives are in the following order: Zn-CDs > Cu-CDs ≫ Mg-CDs > Fe-CDs > U-CDs. Specifically, adding 1.0 wt% of Zn-CDs into water-based lubricant results in 62.5% friction and 81.8% wear reduction. Meanwhile, the load-carrying capacity of the water-based lubricant increases from 120 N to at least 500 N. Zn-CDs as an additive have long service life. Additionally, anion-tuned Zn-CDs fabricated via anion exchange exhibit promise as lubricant additives for poly(ethylene glycol). Based on the results of wear scar surface analyses, it is discovered that tribochemical films, primarily composed of iron oxides, nitrides, metal carbonates, zinc oxides, zinc carbonates, organic compounds, and embedded carbon cores, formed on the rubbing surfaces with a thickness of approximately 270 nm when Zn-CDs are used as additives. This film combined with the “ball-bearing” and third-particle effects of Zn-CDs contributed to excellent lubrication performance.
Aliphatic medium-chain 1-alkenes (MCAEs, ∼10 carbons) are “drop-in” compatible next-generation fuels and precursors to commodity chemicals. Mass production of MCAEs from renewable resources holds ...promise for mitigating dependence on fossil hydrocarbons. An MCAE, such as 1-undecene, is naturally produced by Pseudomonas as a semivolatile metabolite through an unknown biosynthetic pathway. We describe here the discovery of a single gene conserved in Pseudomonas responsible for 1-undecene biosynthesis. The encoded enzyme is able to convert medium-chain fatty acids (C10–C14) into their corresponding terminal olefins using an oxygen-activating, nonheme iron-dependent mechanism. Both biochemical and X-ray crystal structural analyses suggest an unusual mechanism of β-hydrogen abstraction during fatty acid substrate activation. Our discovery unveils previously unidentified chemistry in the nonheme Fe(II) enzyme family, provides an opportunity to explore the biology of 1-undecene in Pseudomonas , and paves the way for tailored bioconversion of renewable raw materials to MCAE-based biofuels and chemical commodities.
Significance We have solved a long-standing mystery of the biosynthetic origin of 1-undecene, a ubiquitous hydrocarbon semivolatile metabolite of Pseudomonas . Our study revealed an unprecedented family of nonheme oxidases that specifically convert medium-chain fatty acids into the corresponding terminal olefins using an oxygen-activating, nonheme iron-dependent mechanism. Our findings unveil previously unidentified chemistry in the nonheme Fe(II) enzyme family, aid the functional study of this ubiquitous metabolite in Pseudomonas , expand the scarce enzyme inventory for the transformation of fatty acid precursors to hydrocarbons, and serve as the basis for engineering efforts to establish bioprocesses to produce medium-chain terminal olefins, useful as fuels and chemical building blocks, from renewable resources.
•US + O3 treatment facilitated the leaching rate of vanadium.•US + O3 treatment promoted the substitution process of SiF bond for SiO bond.•A new technology for enhancing vanadium leaching in a ...low-acid system using US + O3 treatment was developed.•Under the new process, the activation energy of the reaction decreased by 20.19%.•The leaching rate of vanadium increased by 46.7%.
Landfilled metallurgical residues are valuable raw materials for the recovery of strategic vanadium resources. However, efficient separation of vanadium from these residues is challenging due to its strong oxidation resistance and coating within silicate inclusions. To address this issue, this study proposes an enhanced leaching process utilizing the synergistic effect of O3-catalyzed ultrasonic field in a low concentration sulfuric acid system. Results show that following a 10-minute O3 and ultrasonic treatment, the direct leaching rate of vanadium experienced a remarkable 46.7 % increase. Quenching experiments revealed a hierarchical order of active species within the reaction process:⋅OH >⋅O2−> H+, with⋅OH oxidation exhibiting the most pronounced capacity for disrupting the inclusion structure. Electron Paramagnetic Resonance analysis indicated that the highest⋅OH yield arose from the combined application of ultrasound and ozone. Kinetic investigations demonstrated that the vanadium leaching process is governed by interfacial chemical reactions. The activation energy of vanadium oxidation leaching under ultrasonic-O3 conditions was determined to be 40.41 kJ/mol, representing a 20.19 % reduction compared to ultrasonic conditions alone. Through the integration of analysis, characterization, and comparative evaluations, it was discerned that the synergistic impact of ultrasonic and ozone treatments significantly enhances the breakdown of silicate inclusions by low-concentration HF, particularly in the conversion of SiOSi bonds into SiOH bonds and SiF bonds. In summary, the refined leaching methodology incorporating ozone catalysis in conjunction with ultrasonic treatment provides a new idea for the separation and extraction of refractory residual vanadium.
Based on small molecule-linked DNA and the nicking endonuclease-assisted amplification (NEA) strategy, a novel electrochemical method for protein detection is proposed in this work. Specifically, the ...small molecule-linked DNA (probe 1) can be protected from exonuclease-catalyzed digestion upon binding to the protein target of the small molecule, so the DNA strand may hybridize with another DNA strand (probe 2) that is previously immobilized onto an electrode surface. Consequently, the NEA process is triggered, resulting in continuous removal of the DNA strands from the electrode surface, and the blocking effect against the electrochemical species Fe(CN)(6)(3-/4-) becomes increasingly lower; thus, increased electrochemical waves can be achieved. Because the whole process is activated by the target protein, an electrochemical method for protein quantification is developed. Taking folate receptor (FR) as an example in this work, we can determine the protein in a linear range from 0.3 to 15 ng/mL with a detection limit of 0.19 ng/mL. Furthermore, because the method can be used for the assay of FR in serum samples and for the detection of other proteins such as streptavidin by simply changing the small molecule moiety of the DNA probes, this novel method is expected to have great potential applications in the future.
ABSTRACT
Paraneoplastic pemphigus (PNP) is a life‐threatening autoimmune blistering skin disease. Clinically, it is characterized by severe mucosal erosions and various cutaneous lesions associated ...with lymphoproliferative neoplasmas. Suprabasal acantholysis and clefts with scattered necrotic keratinocytes are the unique histopathological features. PNP patient sera recognize multiple antigens, which have been identified as the plakin protein family that includes desmoplakin, bullous pemphigoid antigen I (BPAG1), envoplakin and periplakin, and desmogleins 1 and 3. Castleman's tumor, non‐Hodgkin's lymphoma, thymoma, follicular dendritic cell sarcoma and chronic lymphocytic leukemia are the commonly associated neoplasmas in PNP. We have also demonstrated that the autoantibodies reacting to epidermal proteins are directly produced by the cells in the associated tumors. Bronchiolitis obliterans is frequently found in PNP and may cause respiratory failure and death. In our experience, the early detection and removal of the tumor and i.v. administration of immunoglobulin are critical for the treatment of PNP.
Ex vivo expansion is critical in facilitating the application of hematopoietic/progenitor stem cells (HSPCs) for regenerative therapies. Wnt signaling is implicated in the expansion and self-renewal ...maintenance of HSPCs. However, a reasonable method to regulate Wnt signaling in ex vivo cultures to achieve robust expansion of HSPCs has not yet been investigated. Here, cord blood-derived CD34+ cells were cultured with the activator of Wnt signaling 6-bromoindirubin-3′-oxime (BIO) under the following conditions: vehicle control (group A); BIO was added to the culture on days 0, 4, and 7 (group B); and BIO was added to the culture on days 0 and 7 (group C). Initial BIO treatment promoted the expansion of CD34+ cells on day 4. However, BIO supplementation on days 0 and 4 in group B attenuated HSPC expansion on day 7, while enhancing the multilineage commit potential and secondary expansion ability of expanded CD34+ cells. Based on this finding, an optimized BIO feeding strategy (group C) was proposed to support substantial expansion of HSPCs. After 10 days of culture, the expansion fold of CD34+ cells was 28.70 ± 0.46-folds, which was significantly higher than group A (16.20 ± 0.72-folds, p < 0.05). Moreover, the optimized BIO feeding strategy achieved increased primitive HSPC expansion without the loss of biological functions. Mechanistically, the optimized BIO feeding strategy avoided the excessive activation of Wnt observed in group B while maintaining a moderate level of intracellular β-catenin. These results provide an experimental and theoretical basis for Wnt regulation in ex vivo culture process and a potential strategy to expand HSPCs for transplantation.
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