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71.
《印度化学会志》2023,100(6):101014
In this study, renewable, non-toxic, sulphur free bio-lubricants are synthesized as alternative for fossil fuels. We utilized a bio-derived 10-undecylenic acid (UDA) and pentaerythritol (PE) as raw materials to synthesize bio-lubricants by two-step chemical processes like esterification and followed by epoxidation reactions. And achieved a UDA-PE epoxide yielded 73.4%. The formation of UDA-PE ester and UDA-PE epoxide was confirmed by spectral analysis such as NMR (1H and 13C), FTIR and mass spectra, Physico-chemical and basic lubricant properties by standard American Society for Testing and Materials methods (ASTM). The results showed that the products of UDA-PE ester and UDA-PE epoxide had high viscosity index (262 and 200), good pour points (−29 °C to −15 °C), high flash points (296 °C and 301 °C) respectively and these met the ISO VG (International Organization for Standardization-Viscosity grade) 22 and 220 standard values. In general, both synthesized products are plausible to be employed as bio-lubricant in industrial application. 相似文献
72.
Dr. Shuangyan Hu Lijun Liu Dr. Heng Li Dr. David Pahovnik Prof. Dr. Nikos Hadjichristidis Prof. Dr. Xuechang Zhou Prof. Dr. Junpeng Zhao 《化学:亚洲杂志》2023,18(1):e202201097
A series of ester-ether copolymers were obtained via the reaction between α,ω-dihydroxyl poly(ϵ-caprolactone) (PCL) and ethylene oxide (EO) or monosubstituted epoxides catalyzed by strong phosphazene bases. The two types of monomeric units were distributed in highly random manners due to the concurrence of epoxide ring-opening and fast transesterification reactions. The substituent of epoxide showed an interesting bidirectional effect on the enzymatic degradability of the copolymer. Compared with PCL, copolymers derived from EO exhibited enhanced hydrophilicity and decreased crystallinity which then resulted in higher degradability. For the copolymers derived from propylene oxide and 1,2-butylene oxide, the hydrophobic alkyl pendant groups also allowed lower crystallinity of the copolymers thus higher degradation rates. However, further enlarging the pendant groups by using styrene oxide or 2-ethylhexyl glycidyl ether caused a decrease in the degradation rate, which might be ascribed to the higher bulkiness hindering the contact of ester groups with lipase. 相似文献
73.
A series of novel amide derivatives bearing an indazole moiety were synthesized and evaluated for their in vitro S-adenosyl-L-homocysteine hydrolase (SAHase) inhibitory activity. Among these compounds, 8b, 8m, 8r and 8w showed better or similar inhibitory effects compared to the positive control aristeromycin. These results provide a novel lead for the discovery of more potent non-adenosine analogs as SAHase inhibitors. 相似文献
74.
Jordan DB Li XL Dunlap CA Whitehead TR Cotta MA 《Applied biochemistry and biotechnology》2007,141(1):51-76
β-d-Xylosidase from Selenomonas ruminantium is revealed as the best catalyst known (k
cat, k
cat/K
m) for promoting hydrolysis of 1,4-β-d-xylooligosaccharides. 1H nuclear magnetic resonance experiments indicate the family 43 glycoside hydrolase acts through an inversion mechanism on
substrates 4-nitrophenyl-β-d-xylopyranoside (4NPX) and 1,4-β-d-xylobiose (X2). Progress curves of 4-nitrophenyl-β-d-xylobioside, xylotetraose and xylohexaose reactions indicate that one residue from the nonreducing end of substrate is cleaved
per catalytic cycle without processivity. Values of k
cat and k
cat/K
m decrease for xylooligosaccharides longer than X2, illustrating the importance to catalysis of subsites −1 and +1 and the
lack there of subsite +2. Homology models of the enzyme active site with docked substrates show that subsites bey ond−1 are
blocked by protein and subsites bey ond +1 are not formed; they suggest that D14 and E186 serve catalysis as general base
and general acid, respectively. Individual mutations, D14A and E186A, erode k
cat and k
cat/K
m by <103 and to asimilar extent for substrates 4NPX and 4-nitrophenyl-α-l-arabinofuranoside (4NPA), indicating that the two substrates share the same active site. With 4NPX and 4NPA, pH governs k
cat/K
m with pK
a values of 5.0 and 7.0 assigned to D14 and E186, respectively. k
cat (4NPX) has a pK
a value of 7.0 and k
cat (4NPA) is pH independent above pH 4.0, suggesting that the catalytically inactive, “dianionic” enzyme form (D14-E187-) binds
4NPX but not 4NPA.
The mention of firm names or trade products does not imply that they are end orsed or recommended by the US Department of
Agriculture over other firms or similar products not mentioned. 相似文献
75.
L. Matjka K. Duek P. Chabanne J. P. Pascault 《Journal of polymer science. Part A, Polymer chemistry》1997,35(4):651-663
Network formation in cationic polymerization of polyepoxides was treated using a combination of kinetic theory and the statistical theory of branching processes (TBP). The complex reaction mechanism involved a degradative termination reaction affecting the molecular weight distribution of the primary chains. Moreover, formation of low-molecular-weight products, initiation, two mechanisms of propagation and transfer were taken into account. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 651–663, 1997 相似文献
76.
Katarína uchov Nikolaj Spodsberg Kristian B. R. Mrkeberg Krogh Peter Biely Vladimír Puchart 《Molecules (Basel, Switzerland)》2021,26(15)
This study describes the catalytic properties of a GH30_7 xylanase produced by the fungus Talaromyces leycettanus. The enzyme is an ando-β-1,4-xylanase, showing similar specific activity towards glucuronoxylan, arabinoxylan, and rhodymenan (linear β-1,3-β-1,4-xylan). The heteroxylans are hydrolyzed to a mixture of linear as well as branched β-1,4-xylooligosaccharides that are shorter than the products generated by GH10 and GH11 xylanases. In the rhodymenan hydrolyzate, the linear β-1,4-xylooligosaccharides are accompanied with a series of mixed linkage homologues. Initial hydrolysis of glucuronoxylan resembles the action of other GH30_7 and GH30_8 glucuronoxylanases, resulting in a series of aldouronic acids of a general formula MeGlcA2Xyln. Due to the significant non-specific endoxylanase activity of the enzyme, these acidic products are further attacked in the unbranched regions, finally yielding MeGlcA2Xyl2-3. The accommodation of a substituted xylosyl residue in the −2 subsite also applies in arabinoxylan depolymerization. Moreover, the xylose residue may be arabinosylated at both positions 2 and 3, without negatively affecting the main chain cleavage. The catalytic properties of the enzyme, particularly the great tolerance of the side-chain substituents, make the enzyme attractive for biotechnological applications. The enzyme is also another example of extraordinarily great catalytic diversity among eukaryotic GH30_7 xylanases. 相似文献
77.
A thermophilic microorganism growing within the temperature range of 40–65 °C (optimum at 55 °C) was isolated from hot water
springs near Konkan, Maharashtra, India. Based on 16S rDNA sequence analysis, it was concluded that the isolate belongs to
the genus Brevibacillus. The present paper reports the isolation, identification, and standardization of fermentation conditions for the production
of enzyme, bile salt hydrolase (EC 3.5.1.24) which is produced intracellularly at high temperatures. This is the first report
regarding the production of bile salt hydrolase from a thermophilic source. Optimization of fermentation conditions resulted
in a 2.9-fold enhancement in enzyme production. 相似文献
78.
Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end‐functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl‐modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.g., miktoarm star polymers) is summarized and potential applications as well as future perspectives are discussed.
79.
YU Shanshan ;YIN Hongbing ;WANG Xinying ;FENG Li ;XU Chunchun ;LI Jing ;HAN Hongxiang ;LIU Shuying 《高等学校化学研究》2014,30(5):778-784
A novel thermostable β-galactosidase gene, designated as GkGallA, from the thermophilic bacterium Geobacillus kaustophilus HTA426 was cloned and heterologously overexpressed in Escherichia coli(E, coli). Based on the sequence analysis, GkGallA belongs to the glycosyl hydrolase family 1 that was the first β-galactosidase of bacterial origins expressed by us in this family. The apparent molecular weight of GkGallA determined by sodium deodecyl sulfate-polyacrylamide gel electrophoresis is 52000. It exhibited the highest activity toward p-nitrophenyl-β-D-galactopyranoside at pH 7.8 and 70℃ and displayed high thermal stability, Divalent cations are prerequisite for the activity of GKGallA, with the highest activity in the presence of Mn2+. Moreover, the three-dimensional structure of GkGaI1A was modeled to speculate the structure of the catalytic residues and the reac- tion mechanism. The catalytic residues consisting of Glu166 and Glu355 were verified by site-directed mutagenesis. 相似文献
80.
Cindy B. McReynolds Jun Yang Alonso Guedes Christophe Morisseau Roberto Garcia Heather Knych Caitlin Tearney Briana Hamamoto Sung Hee Hwang Karen Wagner Bruce D. Hammock 《Molecules (Basel, Switzerland)》2021,26(16)
There are few novel therapeutic options available for companion animals, and medications rely heavily on repurposed drugs developed for other species. Considering the diversity of species and breeds in companion animal medicine, comprehensive PK exposures in the companion animal patient is often lacking. The purpose of this paper was to assess the pharmacokinetics after oral and intravenous dosing in domesticated animal species (dogs, cats, and horses) of a novel soluble epoxide hydrolase inhibitor, EC1728, being developed for the treatment of pain in animals. Results: Intravenous and oral administration revealed that bioavailability was similar for dogs, and horses (42 and 50% F) but lower in mice and cats (34 and 8%, respectively). Additionally, clearance was similar between cats and mice, but >2× faster in cats vs. dogs and horses. Efficacy with EC1728 has been demonstrated in mice, dogs, and horses, and despite the rapid clearance of EC1728 in cats, analgesic efficacy was demonstrated in an acute pain model after intravenous but not oral dosing. Conclusion: These results demonstrate that exposures across species can vary, and investigation of therapeutic exposures in target species is needed to provide adequate care that addresses efficacy and avoids toxicity. 相似文献