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961.
962.
Anita Šalić Katarina Pindrić Bruno Zelić 《Applied biochemistry and biotechnology》2013,171(8):2273-2284
Hexanal and hexanoic acid have number of applications in food and cosmetic industry because of their organoleptic characteristics. Problems like low yields, formation of unwanted by-products, and large quantities of waste in their traditional production processes are the reasons for developing new production methods. Biotransformation in a microreactor, as an alternative to classical synthesis processes, is being investigated. Because conditions in microreactors can be precisely controlled, the quality of the product and its purity can also be improved. Biocatalytic oxidation of hexanol to hexanal and hexanoic acid using suspended and immobilized permeabilized whole baker’s yeast cells and suspended and immobilized purified alcohol dehydrogenase (ADH) was investigated in this study. Three different methods for covalent immobilization of biocatalyst were analyzed, and the best method for biocatalyst attachment on microchannel wall was used in the production of hexanal and hexanoic acid. 相似文献
963.
Manish Kumar Suthar Anita Verma Pawan Kumar Doharey Shiv Vardan Singh Jitendra Kumar Saxena 《Applied biochemistry and biotechnology》2013,170(4):868-879
Among various tropical diseases, malaria is a major life-threatening disease caused by Plasmodium parasite. Plasmodium falciparum is responsible for the deadliest form of malaria, so-called cerebral malaria. Purine nucleoside phosphorylase from P. falciparum is a homohexamer containing single tryptophan residue per subunit that accepts inosine and guanosine but not adenosine for its activity. This enzyme has been exploited as drug target against malaria disease. It is important to draw together significant knowledge about inherent properties of this enzyme which will be helpful in better understanding of this drug target. The enzyme shows disorder to order transition during catalysis. The single tryptophan residue residing in conserved region of transition loop is present in purine nucleoside phosphorylases throughout the Plasmodium genus. This active site loop motif is conserved among nucleoside phosphorylases from apicomplexan parasites. Modification of tryptophan residue by N-bromosuccinamide resulted in complete loss of activity showing its importance in catalysis. Inosine was not able to protect enzyme against N-bromosuccinamide modification. Extrinsic fluorescence studies revealed that tryptophan might not be involved in substrate binding. The tryptophan residue localised in electronegative environment showed collisional and static quenching in the presence of quenchers of different polarities. 相似文献
964.
Anita Raj Sanwaria Nikita Sharma Archana Chaudhary Meena Nagar 《Journal of Sol-Gel Science and Technology》2013,68(2):245-253
Non-aqueous reactions of aluminum isopropoxide with 8-hydroxyquinoline (Hq = HONH6C9) in 1:1, 1:2 and 1:3 molar ratios in anhydrous benzene yield complexes of the type [qnAl(OPri)3?n] {where n = 1 (1), n = 2 (2), n = 3 (3)}. Progress of the reactions were monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All the products were fluorescent green powders, sparingly soluble in CHCl3. They were characterized by elemental analysis, FT-IR and (1H, 13C and 27Al) NMR studies. The ESI mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for the compound (3). The XRD spectra of (1–3) showed crystalline nature with the average particle size of 45, 32 and 27 nm respectively, as evaluated from Debye–Scherrer equation. The XRD spectrum of (3) also suggests the formation of β-crystalline polymorphs of Alq3. The SEM images appear to indicate granular morphology for (1) and formation of cylindrical shaped rods for (2) and (3). Sol–gel hydrolysis of (1), (2) or (3) in presence of a strong acid as well as of the precursor, Al(OPri)3,without acid or base catalyst, followed by sintering at 950 °C yielded tetragonal primitive phase of nano-sized δ-alumina in all the cases, as reflected by their powder X-ray diffraction pattern. The IR, SEM and EDX studies also support the formation of transition alumina. 相似文献
965.
966.
Porous chitosan scaffolds with possible tissue engineering applications were synthesized by using lyophilization and supercritical carbon dioxide (sc.CO2) drying technique. 1% Chitosan (CS) solution in aq. acetic acid was treated with 37% formaldehyde solution; the resulting hydrogels were subjected to solvent-exchange prior to the final treatment procedures. Their morphology, pore structure, and physical properties were characterized by Fourier transform infrared spectroscopy (FTIR), thermal analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the specific surface areas and porosities of scaffolds were determined by using N2 adsorption. The sc.CO2 treated scaffolds showed a much greater surface area in comparison to the lyophilized one. Hence, sc.CO2 treated scaffolds is better for cell proliferation. We further investigated the bioactivity of sc.CO2 treated scaffolds using simulated body fluid (SBF). The sc.CO2 assisted chitosan scaffold prepared by using green chemistry approach is highly pure and from a hygienic point of view, it is an ideal material for tissue engineering applications. 相似文献
967.
Priyamvada SHARMA Riya SAILANI Anita MEENA Chandra Lata KHANDELWAL 《Turkish Journal of Chemistry》2020,44(4):950
The kinetic pathway of oxidation of crotyl alcohol by sodium salt of N -chloro-4-methylbenzene sulphonamide (chloramine-T) in acidic and alkaline medium has been studied. The speciation of chloramine-T has been made to suggest a proper and reasonable reaction mechanism. The thermodynamic quantities such as activation energy and activation entropy are evaluated in acidic as well as in catalysed alkaline medium. An anticipated reaction mechanism has been suggested. 相似文献
968.
Aakash D. Nidhankar Goudappagouda Divya S. Mohana Kumari Shailendra Kumar Chaubey Rashmi Nayak Rajesh G. Gonnade G. V. Pavan Kumar Retheesh Krishnan Sukumaran Santhosh Babu 《Angewandte Chemie (International ed. in English)》2020,59(31):13079-13085
Room‐temperature phosphorescence of metal and heavy atom‐free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room‐temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet‐triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6‐phenylmethanone functionalized 9‐hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (>4.1 s) and quantum yield (11 %) owing to an efficient molecular packing in the crystal state. A right‐handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime. 相似文献
969.
970.
Sumit Sood Poonam Kumari Ajar Nath Yadav Anil Kumar Karan Singh 《Journal of heterocyclic chemistry》2020,57(7):2936-2944
An efficient microwave-assisted method of synthesis of pyrazole-4-carbonitriles has been developed. Condensation of pyrazole-4-carbaldehydes with hydroxylamine hydrochloride followed by reaction of the resulting oximes with the Vilsmeier-Haack reagent pre-formed from phthaloyl dichloride and dimethylformamide under microwave irradiation afforded the corresponding pyrazole-4-carbonitriles in 73% to 91% yield. The operational simplicity, avoidance of toxic reagents such as POCl3, shorter reaction time, higher yield compared to the classical version, easy work up, and the use of the by-product in the regeneration of phthaloyl dichloride are the advantages of this methodology. All the target compounds were tested for antimicrobial activity against Gram-positive bacteria Bacillus cereus and Staphylococcus aureus; Gram-negative bacteria Escherichia coli and Yersinia enterocolitica, and the fungal species Candida albicans. 相似文献