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Co-Precipitated Mn0.15Ce0.85O2-delta Catalysts for NO Oxidation: Manganese Precursors and Mn-Ce Interactions
No full textTwo Mn0.15Ce0.85O2-delta mixed oxides were synthesized by a co-precipitation method using Mn(NO3)(2) and KMnO4 as the manganese precursors, respectively. Structural analyses by X-ray powder diffraction and Raman spectroscopy reveal the formation of MnOx-CeO2 solid solutions. The Mn0.15Ce0.85O2-delta catalyst prepared from the high-valent manganese precursor exhibits higher activity for the catalytic oxidation of NO. The advantage of KMnO4 is related to the improved redox property of the catalyst as supported by H-2 temperature-programmed reduction (TPR) and O-2 temperature-programmed desorption (TPD). The Mn-Ce interactions create more Mn4+, Ce3+ and oxygen vacancies on the KMnO4-synthesized mixed oxides based on the Raman and X-ray photoelectron spectra (XPS)
Simulation and design of a heat-integrated double-effect reactive distillation process for propylene glycol methyl ether production
No full textA double-effect reactive distillation (DERD) process was proposed for the production of propylene glycol methyl ether from propylene oxide and methanol to overcome the shortcoming of low selectivity and high-energy consumption in the tubular plug-flow reactor. A single-column reactive distillation (RD) pro-cess was conducted under optimized operating conditions based on sensitivity analysis as a reference. The results demonstrated that the proposed DERD process is able to achieve more than 95% selectivity of the desired product. After that, a design approach of the DERD process with an objective of the min-imum operating cost was proposed to achieve further energy savings in the RD process. The proposed DERD configuration can provide a large energy-savings by totally utilization of the overhead vapor steam in the high-pressure RD column. A comparison of the single-column RD process revealed that the pro-posed DERD process can reduce the operating cost and the total annual cost of 25.3% and 30.7%, respec-tively, even though the total capital cost of DERD process is larger than that of the RD process.(c) 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved
Efficient ultrasound-assisted enzymatic method for extraction of immunostimulant QS-21 from Quillaja saponaria Molina
No full textQS-21 from the bark of Quillaja saponaria Molina is a triterpene glycoside saponin, a new alternative immunoadjuvant. However, its application is limited because its primary source is the bark of adult trees and current extraction methods result in low yields. Therefore, this work aimed at extracting QS-21 from Q. saponaria Molina using a novel and efficient ultrasound-assisted enzymatic extraction (UAEE) method to improve yields and optimize resource utilization. Based on the single-factor and Plackett-Burman design (PBD) experiments, Central Composite design (CCD) optimum extraction conditions for improving QS-21 yield were established (71.084 min incubation time, 275.887 U enzyme dosage, and 20.254 min extraction time, yielding 5.778 mg/g of QS-21). Additionally, compared with ultrasound-assisted extraction (UAE) and enzyme-assisted extraction (EAE) methods, the UAEE method showed a higher QS-21 yield, which was 1.748 and 1.977 times higher than those of the UAE and EAE methods, respectively. Besides, cytotoxicity and immune activation assays indicated that the extract by the UAEE method exhibited a significant inhibitory effect on the activity of bone-marrow-derived dendritic cells and had a high potential for immune activation, respectively. Overall, the UAEE method can successfully improve the extraction yield of QS-21 from Q. saponaria Molina, representing an efficient and resource-saving method to obtain QS-21 for use as an adjuvant in human vaccines
Veiling Effects in the Measurement of Poly-disperse Particles with a Photographic Probe
No full textThe current study aims to clarify how much the measurement results using the image-based method are affected by two types of total overlaps in the images. By ensuring the homogeneous suspension of particles and simultaneous optimiza-tion of the probe location, it has been proven that using the overall holdup of particles as the benchmark data is reasonable. In a bi-disperse particle system, the larger the particles, the more significant the effect of large particles veiling small particles. The maximal relative error nears 50%. In a poly-disperse system, the measurement error heavily depends on the veiled particle size. The larger the particles, the smaller the deviation. For the components of 1 and 3 mm, the relative errors under multiple conditions exceed 50%. The veiling effect of small particles on large particles is qualitatively evaluated. The results of the current study are helpful in promoting the inline image-based method for the actual multiphase reactor method
Surface Self-Assembly of Dipeptides on Porous CaCO3 Particles Promoting Cell Internalization
No full textThe self-assembling behavior of peptides and derivatives is crucial in the natural process to construct various architectures and achieve specific functions. However, the surface or interfacial self assembly, in particular, on the surface of micro-or nanoparticles is even less systematically investigated. Here, uniform porous CaCO3 micro particles were prepared with different charged, hydrophobic and hydrophilic surfaces to assess the self-assembling behavior of dipeptides composed of various sequences. Experimental results indicate that dipeptides with a negative charge in an aqueous solution preferred to self-assemble on the hydrophobic and positively charged surface of CaCO3 particles, which can be ascribed to the electrostatic and hydrophobic interaction between dipeptides and CaCO3 particles. Meanwhile, the Log p (lipid-water partition coefficient) of dipeptides has a significant effect on the self-assembling behavior of dipeptides on the surface of porous CaCO3; dipeptides with high Log p preferred to self-assemble on the surface of CaCO3 particles, resulting in the improved cell internalization efficiency of particles with low cytotoxicity. After loading with a model drug (doxorubicin), the particles show obvious antitumor activity in animal experiments and can reduce Dox side effects effectively
An in vitro assay for enzymatic studies on human ALG13/14 heterodimeric UDP-N-acetylglucosamine transferase
No full textThe second step of eukaryotic lipid-linked oligosaccharide (LLO) biosynthesis is catalyzed by the conserved ALG13/ALG14 heterodimeric UDP-N-acetylglucosamine transferase (GnTase). In humans, mutations in ALG13 or ALG14 lead to severe neurological disorders with a multisystem phenotype, known as ALG13/14-CDG (congenital disorders of glycosylation). How these mutations relate to disease is unknown because to date, a reliable GnTase assay for studying the ALG13/14 complex is lacking. Here we describe the development of a liquid chromatography/mass spectrometry-based quantitative GnTase assay using chemically synthesized GlcNAc-pyrophosphate-dolichol as the acceptor and purified human ALG13/14 dimeric enzyme. This assay enabled us to demonstrate that in contrast to the literature, only the shorter human ALG13 isoform 2, but not the longer isoform 1 forms a functional complex with ALG14 that participates in LLO synthesis. The longer ALG13 isoform 1 does not form a complex with ALG14 and therefore lacks GnTase activity. Importantly, we further established a quantitative assay for GnTase activities of ALG13- and ALG14-CDG variant alleles, demonstrating that GnTase deficiency is the cause of ALG13/14-CDG phenotypes