共查询到20条相似文献,搜索用时 15 毫秒
1.
Báez-Vásquez MA Adrio JL Piret JM Demain AL 《Applied biochemistry and biotechnology》1999,81(3):145-152
Resting cells of Streptomyces clavuligerus NP-1, which posses deacetoxy-cephalosporin C synthase activity, have been shown previously to perform oxidative ring expansion
of penicillin G in the presence of iron, ascorbic acid, and α-ketoglutaric acid to form deacetoxycephalosporin G. Further
studies on this bioconversion indicated that use of MOPS or HEPES buffer at pH 6.5 more than doubled the extent of the reaction
observed with the previously used Tris-HCl at pH 7.4. Levels of bioconversion as high as 16.5% were achieved at low penicillin
G concentrations. Previously, conversion yields were <1%. 相似文献
2.
A. I. Bulavchenko A. T. Arymbaeva M. G. Demidova E. A. Maksimovskii 《Colloid Journal》2011,73(6):748-752
A procedure is elaborated for preparing powders of ammonium and potassium nitrates with microsized particles and stable sols
with particle sizes of 7–16 nm based on isothermal mass crystallization from Tergitol NP-4-stabilized water-in-oil microemulsions
in decane. The crystallization process is studied by turbidimetry and photon-correlation spectroscopy. The isolated powders
are characterized by scanning electron microscopy, while sols and microemulsions are studied by photon-correlation spectroscopy.
Evaporation of water from microemulsion droplets upon stirring water-in-oil micellar solutions at 25–45°C is shown to be the
reason for the salt crystallization. It is ascertained that the time of the onset of crystallization and the morphology of
resulting particles depend on temperature, content of an aqueous pseudophase, and the nature of a salt. A desolubilization-emulsion
hypothesis is proposed for explaining the formation of nanoparticle powders and organosols. 相似文献
3.
The limiting amounts of solubilization of water in the concentration range 0–200 mmol kg–1 polyoxyethylene (6 and 10) nonylphenyl ethers (NP-6 and NP-10)/cyclohexane solutions were measured by the Karl-Fischer method at 25°C. Utilizing NMR, ESR, and near infrared spectroscopic techniques, the states of water in the solubilization region obtained were examined as a function of the molar ratio of water to surfactants at various surfactant concentrations. In NP-6 system, three solubilized states of water, i.e., water interacted directly with the oxyethylene moiety of surfactant, bound water next to the hydrated oxyethylene moiety, and bulk-like water were built up. However, in NP-10 system only directly interacted water was present. It was found that the directly interacted water is distributed between monomeric surfactants and reversed micelles, and others are distributed to swollen micelles and W/O microemulsions. In addition, the minimum amounts of water required to form reversed and swollen micelles were calculated. 相似文献
4.
A series of novel thermo- and pH-sensitive (NP10-AA TPS) hydrogels and microporous (NP10-AA MP) hydrogels, inducing by polyoxyethylene (10) nonyl phenyl ether (NP-10) aqueous two-phase system, was designed and fabricated with acrylic acid (AA) as the monomer for the first time. The resultant NP10-AA TPS hydrogel, compared with the traditional TPS hydrogel, was more advanced in both of the high swelling ratio and the variable lower critical solution temperature (LCST). A simple synthesis technique of the NP10-AA MP hydrogel was developed. The thermo-sensitivity of the NP10-AA TPS hydrogel including the initial swelling ratio, LCST, dehydrated efficiency, was depended strongly on the crosslinker (MBA), initiator (APS), NP-10 and AA concentration. The swelling rate of the NP10-AA MP hydrogel was much higher than that of AA hydrogel dehydrated in the same lyophilization condition. 相似文献
5.
Dynamic surface tensions, σ(t) for aqueous solutions of nonyl phenol ethoxylates (NPEOs) at the temperature 298.15 K were measured using a Lauda drop volume tensiometer. The non-ionic surfactants analyzed in this work were Tergitol NP-9, NP-35 and NP-40. By using the classical Ward and Torday equation, the diffusion coefficient for each bulk surfactant concentration was calculated. The equilibrium surface tension values were determined by extrapolating the dynamic surface tension to t → ∞ on the σ(t) vs. t−1/2 curves. These values were used to determine the critical micelle concentrations (CMC) of the surfactant aqueous solutions as well as to calculate the infinite dilution activity coefficient of the surfactant, following a model that combines the Volmer surface equation of state and the Gibbs adsorption equation. 相似文献
6.
7.
The effect of bond functions on the topological properties of the bonds is studied by performing Hartree-Fock calculations for O2, Cl2, F2, CN–, N2 and LiCl molecules. The results show that bond functions increse the degree of covalency of the bonds and the electronic density at the (3, –1) bond critical point. This effect is quite noticeable for intermediate interactions molecules (F2 and CN–) where a
is obtained instead of a positive value. The optimal position of the bond functions seems to be at or near the (3, –1) bond critical point. 相似文献
8.
Synthesis of Secondary Alcohols and Their Esters from 4-Alkoxy-4-acetyl-1-(2-ethoxyethyl)piperidines
K. D. Praliev I. A. Poplavskaya B. Zh. Nauyryzova M. A. Baimurzina K. D. Botbaeva 《Russian Journal of General Chemistry》2005,75(3):420-424
4-Alkoxy-4-(1-hydroxyethyl)-1-(2-ethoxyethyl)piperidines were prepared by reduction of 4-alkoxy-4-acetyl-1-(2-ethoxyethyl)piperidines. The esters of the hydroxyethyl derivatives were prepared. The presence of an asymmetric carbon atom in the molecules of the carbinols and their esters results in complication of their 1H NMR spectra.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 3, 2005, pp. 456–460.Original Russian Text Copyright © 2005 by Praliev, Poplavskaya, Nauyryzova, Baimurzina, Botbaeva. 相似文献
9.
The effects of vitamins B1, B2, and B6 and pyridoxal phosphate on the formation of the final radiolysis products of aqueous ethanol and ethylene glycol solutions were studied. It was found that vitamin B2 and pyridoxal phosphate effectively oxidize R·CHOH species to suppress their recombination and fragmentation reactions, thereby increasing the yields of corresponding oxidation products. Vitamins B1 and B6 are capable of reducing alcohol radicals to the parent molecules and, hence, decreasing the yields of the main radiolysis products.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 325–329.Original Russian Text Copyright © 2005 by Lagutin, Shadyro. 相似文献
10.
Yu. G. Egiazarov V. S. Soldatov L. Yu. Tychinskaya L. N. Shachenkova B. Kh. Cherches E. N. Ermolenko 《Kinetics and Catalysis》2005,46(4):502-508
The catalytic properties of the fibrous sulfonic acid cation exchanger FIBAN K-1 in methyl tert-amyl ether synthesis are studied as a function of its water content. Reducing the degree of hydration of the cation exchanger to <2 H2O molecules per SO3H group diminishes the proportion of the desired product in the catalysate. According to 13C NMR data, protonation of methylbutenes in the air-dry cation exchanger phase (which contains 4 H2O molecules per SO3H group) involves [nH2O] ⋅ H+ species and is accompanied by olefin hydration and the formation of protonated tert-amyl alcohol.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 536–542.Original Russian Text Copyright © 2005 by Egiazarov, Soldatov, Tychinskaya, Shachenkova, Cherches, Ermolenko. 相似文献
11.
Yue Wu Yanqiong Yang Dr. Yan Zhang Dr. Liwei Dai Dr. Wenhao Dong Dr. Huibin He Dr. Hao Li Prof. Dr. Zhihong Nie Prof. Dr. Yutao Sang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202313406
Colloidal molecules (CMs) are precisely defined assemblies of nanoparticles (NPs) that mimic the structure of real molecules, but externally programming the precise self-assembly of CMs is still challenging. In this work, we show that the photo-induced self-assembly of complementary copolymer-capped binary NPs can be precisely controlled to form clustered AB x or linear ( AB ) y CMs at high yield (x is the coordination number of NP- B s, and y is the repeating unit number of AB clusters). Under UV light irradiation, photolabile p-methoxyphenacyl groups of copolymers on NP- A *s are converted to carboxyl groups (NP- A ), which react with tertiary amines of copolymers on NP- B to trigger the directional NP bonding. The x value of AB x can be precisely controlled between 1 and 3 by varying the irradiation duration and hence the amount of carboxyl groups generated on NP- A s. Moreover, when NP- A * and NP- B are irradiated after mixing, the assembly process generates AB clusters or linear ( AB ) y structures with alternating sequence of the binary NPs. This assembly approach offers a simple yet non-invasive way to externally regulate the formation of various CMs on demand without the need of redesigning the surface chemistry of NPs for use in drug delivery, diagnostics, optoelectronics, and plasmonic devices. 相似文献
12.
A. N. Chekhlov 《Russian Journal of General Chemistry》2005,75(11):1808-1811
The crystal and molecular structure of (trans-3,4-diamino-2,2,6,6-tetramethylpiperidine-1-oxyl-N
3, N
4)(oxalato-O,O′)platinum(II) dihydrate was studied by single crystal X-ray diffraction. The crystals belong to the monoclinic system; a 8.261, b 13.129, c 15.224 Å; β 104.29°, Z 4, space group P21/n. The structure was solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation
to R 0.026 for all the 3660 measured unique reflections. The structure consists of individual mononuclear bischelate molecules
containing two different bidentate ligands. The Pt2+ coordination is distorted square-planar. The complex molecules and water molecules in the crystal of I are linked by hydrogen bonds forming an infinite 3D network.
__________
Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 11, 2005, pp. 1893–1897.
Original Russian Text Copyright ? 2005 by Chekhlov. 相似文献
13.
Immunoenzyme assay of nonylphenol: study of selectivity and detection of alkylphenolic non-ionic surfactants in water samples 总被引:1,自引:0,他引:1
Mart'ianov AA Dzantiev BB Zherdev AV Eremin SA Cespedes R Petrovic M Barcelo D 《Talanta》2005,65(2):367-374
Immunoenzyme assay (ELISA) is proposed and characterized for determination of alkylphenol ethoxylates, a primary class of manufactured non-ionic surfactants. The assay is based on the obtained polyclonal antibodies against nonylphenol (NP), the main stable intermediate of the decomposition of nonylphenol ethoxylates. A mixture of non-modified branched isomers of NP was applied as hapten coupled to protein carriers by Mannich reaction with the use of formaldehyde. The proposed ELISA format is based on immobilized NP-(soybean trypsin inhibitor) conjugate as a competitor of antigen molecules contained in the tested sample for binding with specific antibodies indirectly labeled via an anti-species immunoperoxidase conjugate. The developed ELISA allows to reveal NP with the limit of detection about 10 ng ml−1 and NP-related compounds such as octylphenol, alkylphenoletoxylates, alkylphenolcarboxylates and their halogenated derivatives. The ELISA was applied for assaying polluted water samples, namely influents and effluents from different wastewater treatment plants (WWTP) and tap water. ELISA and chromatographic data demonstrate good correlation (r = 0.94), while ELISA gives higher values. Due to endocrine disrupting and other toxic activities of some metabolites of alkylphenolic non-ionic surfactants, the developed assay may be effectively used in ecological monitoring and sanitary control. 相似文献
14.
A. I. Kuramshin E. A. Kuramshina R. A. Cherkasov 《Russian Journal of Organic Chemistry》2005,41(5):649-655
At the use of photochemical and thermochemical activation new π-complexes of chromium, molybdenum, and tungsten were prepared containing in the coordination sphere η2- and η4-molecules of 4-methyl-3-penten-2-one. Nonempirical methods were applied to calculation of the energy parameters of the coordinated molecules, and the factors governing the η2- and η4-coordination of the oxodiene system were established. A thermochemical study was performed on the 4-methyl-3-penten-2-one η4-coordination product with carbonyl metal core. A scheme of the thermal decomposition was suggested for the iron (0) η 4-(4-methyl-3-penten-2-one)tricarbonyl.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 665–671.Original Russian Text Copyright © 2005 by Kuramshin, Kuramshina, Cherkasov. 相似文献
15.
Chikashi Nakanishi Saori Ikeda Tetsuhiko Isobe Mamoru Senna 《Journal of Sol-Gel Science and Technology》2003,26(1-3):103-106
Silica fine particles in a single or sub-micrometer regime, containing FeCl3 and 2,2-bipyridine (bpy), were prepared by utilizing reverse micellar method. Formation of tris-bpy iron(II) ([Fe(bpy)3]2+) complex was induced in the silica fine particles by UV irradiation at 365 nm. The starting micellar solution was obtained by an injection of 0.04 cm3 HCl aqueous solution into 5 cm3 tetraethyl orthosilicate (TEOS)/cyclohexane (2 cm3/3 cm3) mixed solution containing 4–14 vol% of nonionic surfactant, polyoxyethylene(5) nonylphenyl ether (NP-5). Size of the silica particles was regulated by the concentration of NP-5. 相似文献
16.
A. I. Kuramshin E. V. Asafyeva R. A. Cherkasov 《Russian Journal of Organic Chemistry》2005,41(5):779-783
New tungsten complexes were prepared of a composition η3-[(1,3,5-triorganyl)-1,3,5-triazacyclohexane]-tricarbonyltungsten(0) where a tridentate coordination of the triazinane fragment to the metal center was found. The reaction of tricarbonyltriazinane tungsten complexes with 1,3-diphenyl-2-propen-1-one (chalcone) under thermochemical activation resulted in replacement of two carbon monoxide molecules in the coordination sphere of tungsten by a chalcone molecule linked to the transition metal atom through a system of π-bonds C=C and C=O. The phosphorylation of η4-(1,3-diphenyl-2-propen-1-one)-η3-[(1,3,5-triphenyl)-1,3,5-triazacyclohexane]-monocarbonyltungsten(0) with diethyl phosphite occurred at the carbonyl group of the coordinated heterodiene; the phosphonate thus formed underwent intracomplex phosphonate-phosphate rearrangement affording an organometallic phosphate.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 793–797.Original Russian Text Copyright © 2005 by Kuramshin, Asafyeva, Cherkasov. 相似文献
17.
Yu. E. Zevatskii 《Russian Journal of Applied Chemistry》2005,78(3):461-464
A method is suggested for relating the relative permittivity, ionization potential, polarizability, and linear dimensions of nonpolar molecules. This was demonstrated for the example of inert gases, some spherical- and symmetric-top molecules, and linear molecules.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 466–469.Original Russian Text Copyright © 2005 by Zevatskii. 相似文献
18.
The structures of the title compounds are mononuclear with each lanthanide bound by a single η5‐fluorenyl ligand, two trans‐disposed iodides and three meridionally oriented pyridine molecules. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
19.
A. E. Galashev O. R. Rakhmanova L. A. Zemnukhova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(6):955-960
The effect of absorbed water on the dielectric properties of silicon dioxide nanoparticles is studied by the molecular dynamic
method. It is demonstrated using the model of flexible molecules that increasing the number of water molecules in the (SiO2)50 cluster to 40 results in an enhancement of absorption of infrared radiation over the frequency range 0 cm−1 ≤ ω ≤ 1000 cm−1. It is ascertained that the absorption of water molecules by the (SiO2)50 cluster considerably alters the shape of Raman spectra of light, smoothing all the peaks after the first one, and that water
molecules are concentrated near the cluster surface formed by SiO2 structural units. 相似文献
20.
Bonzagni Neil J. Baker Gary A. Pandey Siddharth Niemeyer Emily D. Bright Frank V. 《Journal of Sol-Gel Science and Technology》2000,17(1):83-90
Steady-state and time-resolved fluorescence spectroscopy are used to determine the local microheterogeneity surrounding pyrene molecules sequestered within tetramethylorthosilicate-derived xerogels. After compensation for the intrinsic background emission from the xerogel, we find that the pyrene intensity decay kinetics are best described by a two-term rate law. This is consistent with the pyrene molecules distributing primarily into two microenvironments. Under ambient conditions, the individual pyrene microenvironments exhibit excited-state fluorescence lifetimes that differ by 100 ns. However, the pyrene I1 to I3 band ratios that are associated with each microenvironment are statistically equivalent to one another. These results show that the local dipolarity surrounding these pyrene microenvironments are similar, but the decay rates associated with each microenvironment are very different. The longer-lived pyrene species (Environment #1) constitutes 1/2 of the total fluorescence and it exhibits an O2 quenching sensitivity (Ksv1) of (5.19 ± 0.52 × 10–3 %O2
–1 and a bimolecular quenching constant (kq1) of (2.30 ± 0.23) × 104 %O2
–1 s–1. Environment #2, associated with the shorter-lived pyrene species, exhibits an O2 quenching sensitivity (Ksv2) of (2.31 ± 0.16) × 10–2 %O2
–1 and a bimolecular quenching constant (kq2) of (2.11 ± 0.23) × 105 %O2
–1 s–1. These results are interpreted as follows: Environment #1 consists of pyrene molecules sequestered within a relatively rigid siloxane network wherein non-radiative decay pathways are lessened, but these pyrene molecules are not quenched readily by O2. Environment #2 consists of pyrene molecules adsorbed onto surface silanols within the xerogel. These pyrene molecules are quenched by the silanols and they are simultaneously more accessible to O2 compared to Environment #1. 相似文献