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21.
Aguilar CN Favela-Torres E Viniegra-González G Augur C 《Applied biochemistry and biotechnology》2002,102(1-6):407-414
Undesirable protease production by Aspergillus niger Aa-20 in submerged culture and solid-state culture was evaluated using different concentrations of tannic acid as sole carbon
source in a model system designed for tannase production. Protease production was found to be dependent on the culture system
used (submerged culture or solid-state culture) and on the initial tannic acid concentration. Expression of protease activity
in submerged culture was higher (up to 10 times) than activity obtained in solid-state culture, using identical culture medium
composition. In submerged culture, the lowest final protease activity (0.13 IU) was obtained with the highest tannic acid
concentration, while in solid-state culture protease activity was not affected by changes in initial substrate concentration.
Absence of detectable proteolytic activity in solid-state culture is related to high production of tannase enzyme. Hence,
the use of solid-state culture for fungal enzyme production may allow for higher and more stable enzyme titers present in
culture extracts. 相似文献
22.
张雨文 《广东微量元素科学》2003,10(7):61-63
老年人由于组织器官的老化和功能减退,影响药物的吸收、分布、代谢和排泄。为确保老年患者的用药安全,应提高老年人的合理用药水平。 相似文献
23.
Dr. Samuel Oger Damien Schapman Dr. Romain Mougeot Dr. Stéphane Leleu Dr. Noëlle Lascoux Dr. Patrice Baldeck Dr. Magalie Bénard Dr. Thibault Gallavardin Dr. Ludovic Galas Dr. Xavier Franck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10954-10964
Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus. 相似文献
24.
Potential energy functions suitable for the (Cs1–xNaxT2O4)-A type zeolite family were obtained from the known crystal structure of Cs7Na5-A zeolite. Using these potential functions, several other crystal structures in these family were obtained by molecular mechanical calculations. The activation energy - to -cage transmission of the H2 molecule and the void volume of Cs3Na9-A zeolite were calculated. 相似文献
25.
K. No Hyun J. Lee Ki M. Park Shim S. Lee Kwan H. Noh Sung K. Kim Ji Y. Lee Jong S. Kim 《Journal of heterocyclic chemistry》2004,41(2):211-219
A series of novel 1,3‐altemate calix[4]arene azacrowns having mono and bis crown ethers on the lower rim of the calix[4]arene framework were synthesized. Solid‐state structures confirmed the three dimensional conformation of compounds 1–3. 相似文献
26.
Chardon-Noblat S Horner O Chabut B Avenier F Debaecker N Jones P Pécaut J Dubois L Jeandey C Oddou JL Deronzier A Latour JM 《Inorganic chemistry》2004,43(5):1638-1648
Reaction of the unsymmetrical phenol ligand 2-((bis(2-pyridylmethyl)amino)methyl)-6-(((2-pyridylmethyl)benzylamino)methyl)-4-methylphenol (HL-Bn) or its 2,6-dichlorobenzyl analogue (HL-BnCl(2)) with Fe(H(2)O)(6)(ClO(4))(2) in the presence of disodium m-phenylenedipropionate (Na(2)(mpdp)) followed by exposure to atmosphere affords the diiron(II,III) complexes [Fe(2)(L-Bn)(mpdp)(H(2)O)](ClO(4))(2) and [Fe(2)(L-BnCl(2))(mpdp)(CH(3)OH)](ClO(4))(2), respectively. The latter complex has been characterized by X-ray crystallography. It crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.3095(14) A, b = 20.1073(19) A, c = 19.4997(19) A, alpha = 90 degrees, beta = 94.471(2) degrees, gamma = 90 degrees, V = 5202.6(9) A(3), and Z = 4. The structure of the compound is very similar to that of [Fe(2)(L-Bn)(mpdp)(H(2)O)](BPh(4))(2) determined earlier, except for the replacement of a water by a methanol on the ferrous site. Magnetic measurements of [Fe(2)(L-Bn)(mpdp)(H(2)O)](BPh(4))(2) reveal that the two high-spin Fe ions are moderately antiferromagnetically coupled (J = -3.2(2) cm(-)(1)). Upon dissolution in acetonitrile the terminal ligand on the ferrous site is replaced by a solvent molecule. The acetonitrile-water exchange has been investigated by various spectroscopic techniques (UV-visible, NMR, M?ssbauer) and electrochemistry. The substitution of acetonitrile by water is clearly evidenced by M?ssbauer spectroscopy by a reduction of the quadrupole splitting value from 3.14 to 2.41 mm/s. In addition, it causes a 210 mV downshift of the oxidation potential of the ferrous site and a similar reduction of the stability domain of the mixed-valence state. Exhaustive electrolysis of a solution of [Fe(2)(L-Bn)(mpdp)(H(2)O)](2+) shows that the aqua diferric species is not stable and undergoes a chemical reaction which can be partly reversed by reduction to the mixed-valent state. This and other electrochemical observations suggest that upon oxidation of the diiron center to the diferric state the aqua ligand is deprotonated to a hydroxo. This hypothesis is supported by M?ssbauer spectroscopy. Indeed, this species possesses a large quadrupole splitting value (DeltaE(Q) >or= 1.0 mm.s(-)(1)) similar to that of analogous complexes with a terminal phenolate ligand. This study illustrates the drastic effects of aqua ligand exchange and deprotonation on the electronic structure and redox potentials of diiron centers. 相似文献
27.
Noëlle Ehlinger Monique Perrin 《Journal of inclusion phenomena and macrocyclic chemistry》1995,22(1):33-40
The structure of thep-tetrakis-(4-nitrophenylazo)calix[4]arene-4-picoline (14) complex has been determined by X-ray crystallography. Crystals are monoclinic, space groupC2/c,a=24.9097) Å,b=8.425(6) Å,c=33.81(1) Å, =101.13(2)°,D
c
=1.330 g/cm3,Z=4, finalR value =0.067. The cone conformation adopted by this azocalixarene is disturbed by the positions of the picoline molecules. Two of them are inside the macorocycle cavity and the two others are outside.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. Sup. 82190 (32 pages). 相似文献
28.
Leufroy A Noël L Beauchemin D Guérin T 《Analytical and bioanalytical chemistry》2012,402(9):2849-2859
A continuous leaching method coupled online with inductively coupled plasma mass spectrometry (ICP-MS) detection was used
to assess the maximum bioaccessibility of arsenic (As) in seafood samples. The method simulates continuous-flow digestion
by successively pumping artificial saliva, gastric and intestinal juices through a mini-column of powdered sample directly
connected to the nebuliser of an ICP-MS instrument. The method allows the real-time measurement of As being released by a
given reagent. Because the analyte is continuously removed from the system, in contrast to batch methods, the dissolution
equilibrium is driven to the right, hence quickly providing information about the worst-case scenario. Following consecutive
leaching by the digestive reagents, the leachates were subject to speciation analysis by ion-exchange chromatography with
ICP-MS detection to determine the arsenic species released. Finally, the remaining residue from the mini-column was fully
digested to verify mass balance. The method was used to determine the bioaccessibility of total As and As species in four
certified reference materials and in several real seafood samples. The mass balance was verified in each case. Generally speaking,
the non-toxic form was easily released whereas the inorganic forms were poorly bioaccessible. 相似文献
29.
Chadi Khoury François Le Goffic Marie‐Noëlle Rager 《Journal of carbohydrate chemistry》2013,32(7):395-409
The synthesis of 2‐acetamido‐2‐deoxy‐6‐O‐octanoyl‐D‐glucono‐1,5‐lactone 9 and 2‐acetamido‐2‐deoxy‐6‐O‐octanoyl‐α‐D‐glucopyranose 7 from 2‐acetamido‐2‐deoxy‐α‐D‐glucopyranose is reported. For both targets, the key intermediate was allyl 2‐acetamido‐3,4‐di‐O‐benzyl‐2‐deoxy‐6‐O‐octanoyl‐α‐D‐glucopyranoside 5. Surface tension measurements (critical micellar concentration of 22.3 mM and 5 mM for 9 and 7, respectively) showed up the surface activity of both compounds, while enzyme inhibition assays indicated that 9 could inhibit bovine β‐N‐acetylglucosaminidase (Ki=6.5 µM) but not Serratia marcescens chitobiase nor hen egg‐white lysozyme. Moreover, 7 was shown to induce chitinase production of S. marcescens and to be readily metabolized by these bacteria. 相似文献
30.
Roitershtein D Domingos A Pereira LC Ascenso JR Marques N 《Inorganic chemistry》2003,42(23):7666-7673
Reaction of yttrium and lanthanum trichloride with 1 equiv of sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate and 1 equiv of 2,2'-bipyridine gives good yields of the complexes [MCl(2)(Tp(Me2))(C(10)H(8)N(2))] (M = Y (1), La (2)). The analogous compounds with 1,10-phenanthroline, [MCl(2)(Tp(Me2))(C(12)H(8)N(2))] (M = Y (3), La (4)), have been obtained by a similar procedure. The solid-state structures of 2-4 were determined by single-crystal X-ray diffraction and revealed that the compounds are all seven-coordinate with capped octahedral geometry. In contrast, reaction of yttrium trichloride with 1 equiv of sodium hydrotris(3,5-dimethylpyrazolyl)borate in the presence of 1 equiv of neocuproine affords [YCl(3)(Tp(Me2))][Na(neoc)(3))] (5). Compounds 1 and 2 provide an entry for the synthesis of complexes containing the bipyridyl ligand in a radical anionic form or in a dianionic form. Reaction of 1 and 2 with an excess of sodium amalgam gives [Y(Tp(Me2))(bipy)(THF)(2)] (6) and [La(Tp(Me2))(2)(bipy)] (7), respectively. The structures of both compounds have been determined by X-ray crystallography. Compound 7 can be oxidized with iodine to give [La(Tp(Me2))(2)(bipy)]I (8). 相似文献