共查询到20条相似文献,搜索用时 31 毫秒
1.
Shekhar Kumar U. Kamachi Mudali R. Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):717-720
Conventionally composition of the actinide-extractant solvate is assumed to be the same in the unpartitioned organic phase
and the formed third phase. For example, if a m:n solvate has formed during extraction, the solvate is expected to be in the
same state even during the third phase condition. However contemporary analysis, based on the spectroscopy measurements and
empirical observations, has indicated the presence of an extended solvate. In this article, the proposed speciation in nitric
acid and U(VI) third phase formation in n–n dialkyl amide/dodecane-nitric acid systems has been modeled with empirical correlations. 相似文献
2.
Photosubstitution of the sulfo group for hydrogen (chlorine in chloranil) is observed under irradiation of sulfonated derivatives
of hydroquinone formed upon dissolving of p-benzoquinone and p-chloranil in aqueous solutions of sodium sulfite. The quantum yield of the photochemical reaction is 0.18 ± 0.02 for p-benzoquinone. The rate constant of the thermal reaction of substitution is 5.5 × 10−4 l mol−1 s−1. The substitution reaction is sensitized by eosin upon irradiation with visible light. During the course of irradiation of
sulfohydroquinones, the formation of a product with an absorption maximum at 235 nm was found. The product decays with a rate
constant of 0.005 s−1. 相似文献
3.
A nonlabeling electrochemical detection method for analyzing the polymerase-chain-reaction-amplified sequence-specific p16
INK4A
gene, in which the basis for the covalent immobilization of deoxyribonucleic acid (DNA) probe is described, has been developed.
The self-assembly process was based on the covalent coupling of glutaraldehyde (GA) as an arm molecule onto an amino-functional
surface. The p16
INK4A
gene was used as the model target for the methylation detection of early cancer diagnosis. An amino-modified DNA probe was
successfully assembled on the GA-coupling surface through the formation of Schiff base under potential control. The hybridization
of amino-modified DNA probes with the target was investigated by means of electrochemical measurements, including cyclic voltammetry
and square wave voltammetry. Furthermore, the functions of GA coupling for sequence-specific detection were compared with
those obtained based on mercaptopropionic acid. Hybridization experiments indicated that the covalent coupling of GA was suitable
for the immobilization of DNA probe and was sensitive to the electrochemical detection of single-base mismatches of label-free
DNA targets in hybridization. Moreover, reported probe-modified surfaces exhibited excellent stability, and the hybridization
reactions were found to be completely reversible and highly specific for recognition in subsequent hybridization processes.
The strategy provided the potential for taking full advantage of existing modified electrode technologies and was verified
in microarray technology, which could be applied as a useful and powerful tool in electrochemical biosensor and microarray
technology. 相似文献
4.
E. B. Tarabukina N. V. Zakharova M. S. Borisenko M. V. Solovskii 《Polymer Science Series A》2017,59(3):295-300
The random copolymers of N-vinylpyrrolidone and N-crotonoylaminocaproic acid attractive for the modification of drugs are studied by static and dynamic light scattering, viscometry, and sedimentation-diffusion analysis. The content of functional groups in the copolymers is 14.1–27.0 mol %. Analysis is performed in 0.1 N aqueous solutions of sodium acetate and dimethylformamide. The molecular characteristics of the copolymers with various composition are determined. It is shown that supramolecular structures are present in copolymer solutions and their amount depends on copolymer composition; the effect of solvent on the formation of these structures is ascertained. 相似文献
5.
For HF solutions in DMF, concentration-dependent fractions of DMF molecules (α(DMF)) that remain unassociated and that enter heteroassociates (HAs) of 1 : 1, 4 : 1, and 12 : 1 molecular stoichiometries were obtained by two independent methods, namely, from an analysis of IR spectra and by calculating the material balance. The experimental way was shown to be enough exact in determining the ratio between the solvent molecules in four different states up to ~83 mol % HF. The equilibrium compositions of HF–DMF solutions were estimated over the entire range of concentrations. Starting with [HF] of ~25 mol %, more than one-half HF molecules are associated, and at [HF] of ~50–92 mol %, at least 90% of the HF molecules are associated. The equilibrium composition of HF–organic solvent (Solv) solutions in which HAs of 1 : 1, 1 : 4, and 1 : 12 molecular stoichiometries are formed, can be described by a single set of α(HF–Solv) versus concentration plots. 相似文献
6.
A. V. Lezov G. E. Polushina A. A. Lezov P. S. Vlasov N. S. Domnina 《Polymer Science Series A》2011,53(2):93-101
The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH
values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied.
For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the
chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes.
In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid
units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer
and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the
copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm.
The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to
steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of
the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along
the chain contour. 相似文献
7.
T. F. Ibragimov M. G. Levkovich V. A. Saprykina Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2010,46(5):767-770
N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The
point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated. 相似文献
8.
R. A. Cherkasov A. R. Garifzyanov O. B. Bazanova S. V. Leont’eva 《Russian Journal of General Chemistry》2011,81(10):2080-2087
The processes were studied of the solvent extraction of the ions of triply-charged trace elements including scandium, indium,
gallium, and yttrium, as well as iron, with N-octyl-N,N-bis(dihexylphosphinylmethyl) amine solution in toluene, chloroform or methylene chloride from hydrochloric, nitric or perchloric
acids aqueous solutions. The metals extraction dependence on the acid concentration showed that the best results were reached
using perchloric acid. The calculation of partition coefficients of metals allowed us to reveal a high selectivity of the
scandium extraction. The prospects of using the investigated bisphosphinylamine in the technology of extraction, concentration
and separation of the trace metals ions was concluded. 相似文献
9.
Corncob is an economic feedstock and more than 20 million tons of corncobs are produced annually in China. Abundant xylose
can be potentially converted from the large amount of hemicellulosic materials in corncobs, which makes the crop residue an
attractive alternative substrate for a value-added production of a variety of bioproducts. Lactic acid can be used as a precursor
for poly-lactic acid production. Although current industrial lactic acid is produced by lactic acid bacteria using enriched
medium, production by Rhizopus oryzae is preferred due to its exclusive formation of the l-isomer and a simple nutrition requirement by the fungus. Production of l-(+)-lactic acid by R. oryzae using xylose has been reported; however, its yield and conversion rate are poor compared with that of using glucose. In this
study, we report an adapted R. oryzae strain HZS6 that significantly improved efficiency of substrate utilization and enhanced production of l-(+)-lactic acid from corncob hydrolysate. It increased l-(+)-lactic acid final concentration, yield, and volumetric productivity more than twofold compared with its parental strain.
The optimized growth and fermentation conditions for Strain HZS6 were defined. 相似文献
10.
Decomposition of a series of N-cyclopropyl-N-nitrosoureas (CNU) in CD3OD was studied. These decompose much more rapidly than N-methyl-N-nitrosourea, one of the decomposition pathways being denitrosation, which is atypical of alkylnitrosoureas under the reaction conditions used. The nature of substituents in the cyclopropane ring has a great effect on the stability of CNU and the product ratio. In the presence of H2 SO4, decomposition occurs much more rapidly. Possible pathways of the formation of the major decomposition products of CNU are proposed based on the experimental data.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 359–370, February, 2005. 相似文献
11.
The photochemical reaction of o-iodo- and o-bromophenol in an aqueous sodium sulfite solution proceeds via both nonchain and chain mechanisms. The formation of the intermediate
product, aromatic radical anion, was observed. The quantum yield of the photochemical reaction of o-iodophenol increases, when the electron donor diphenylamine is irradiated. In the photolysis of o-halophenols in organic solvents, free iodine is evolved in addition to aromatic products. The products of the photolysis
of o-iodophenol in ethanol and carbon tetrachloride were identified by gas chromatography-mass spectrometry. These are phenol
in the case of ethanol and a mixture of o-chlorophenol and hydroxychloro-substituted biphenyls in the case of carbon tetrachloride. The quantum yields were determined
for all photochemical reactions studied. 相似文献
12.
D. G. Cherkasov M. P. Smotrov K. K. Il’in 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(6):922-927
Phase equilibria and critical phenomena in the potassium nitrate-water-n-butoxyethanol ternary system were studied by the visual polythermal method over the temperature range 10–150°C. In this system,
the boundary binary liquid system is characterized by the presence of a closed stratification region. The temperature of the
formation of a critical tie line of monotectic equilibrium (18.3°C) and solution compositions corresponding to the critical
solubility points at various temperatures were determined. The n-butoxyethanol distribution coefficients between the aqueous and organic phases of the monotectic state were calculated at
eight temperatures. n-Butoxyethanol salting out from aqueous solutions by potassium nitrate increased as the temperature grew. The generalized
scheme of topological transformations of salt-binary solvent ternary system phase diagrams with salting out was substantiated
and augmented. 相似文献
13.
I. E. Efremova M. I. Vakulenko K. A. Lysenko I. S. Bushmarinov L. V. Lapshina G. A. Berkova V. M. Berestovitskaya 《Russian Journal of General Chemistry》2010,80(11):2298-2305
A modification of 1-nitrocyclohexene synthesis is proposed; its reaction with phenylhydrazine and benzoic acid hydrazide is
shown to afford monoadducts, and with hydrazine hydrate, bisaduct. With diphenylguanidine occurs heterocyclization to 1-phenyl-2-N-phenylamino-4,5,6,7-tetrahydrobenzimidazole, whose structure is confirmed by the X-ray diffraction data. The analysis performed
for this compound of the electron density distribution function in the crystal made it possible to estimate the charge distribution,
π-electrons delocalization nature, and the role of N-H…N, C-H…H-C and C-H…C interactions in the formation of the crystal packing. 相似文献
14.
Analysis of cellulose biosynthesis using molecular approaches has been successful in identifying genes in many cellulose-producing
organisms, yet the mechanism of cellulose biosynthesis still remains to be understood. We are interested in developing the
moss Physcomitrella patens as a useful system for the study of cellulose biosynthesis. This moss affords a number of advantages including a haploid
dominated gametophyte and a very high efficiency of homologous recombination in its nuclear DNA for constructing gene knockouts.
In addition, P. patens has only a primary cell wall unlike Arabidopsis thaliana, which has both a primary and a secondary cell wall. We identified two full-length cellulose synthase (CesA) genes of P. patens, PpCesA6 and PpCesA7 from an EST database and have analyzed the genomic sequences. PpCesA6 and PpCesA7 show high similarity to each other, both at the cDNA and genomic DNA levels. Single and double knockouts of PpCesA6 and PpCesA7 were generated and screened for phenotypic changes. While the PpCesA6 and PpCesA7 single knockouts did not show any obvious phenotypic differences from the wild-type, the double knockout had significantly
reduced stem length. These results suggest that PpCesA6 and PpCesA7 probably have a very similar role in cellulose biosynthesis and their functions may be redundant. Additionally, their roles
may overlap with the other P. patens CesAs as observed for CesAs involved in primary cell wall biosynthesis in A. thaliana. 相似文献
15.
Different from organic solvent, self-assemblies are environment friendly media, and moreover, if they are used as micro-reactor,
many meaningful and exciting results may be obtained. In this paper, we investigated the photoisomerization of trans-stilbene in Triton X-100/n-C5H11OH/H2O microemulsions (a kind of self-assemblies) with different compositions and structures to establish the relationship between
the reaction yields and the compositions and structures of microemulsions. The results show that the yield of cis-stilbene is increased with the increase of water content or with the decrease of Triton X-100 content, and oil in water (O/W)
structure is the best structure for this reaction, which makes it possible to decrease the pollution of environment by organic
solvent always used in organic reactions. 相似文献
16.
Ermakova S Sokolova R Kim SM Um BH Isakov V Zvyagintseva T 《Applied biochemistry and biotechnology》2011,164(6):841-850
Fucoidans were isolated by water extraction and ion-exchange chromatography from brown algae Eclonia cava, Sargassum hornery, and Costaria costata collected near of Korean coasts. The structures of fucoidans were investigated. Fucoidan from E. cava was mixture of sulfated rhamnogalactofucan and galactofucan. Fucoidan from C. costata was a sulfated galactofucan. Fucoidan isolated from S. hornery was separated into three fractions: a homofucan sulfate, a homofucan but without sulfate groups, and a sulfated rhamnofucan.
The results clearly showed that fucoidans play an inhibitory role in colony formation in human melanoma and colon cancer cells
and may be effective antitumor agents. 相似文献
17.
Jungang Gao X. Zhang L. Huo H. Zhao 《Journal of Thermal Analysis and Calorimetry》2010,100(1):225-232
The curing kinetics of a bi-component system about o-cresol-formaldehyde epoxy resin (o-CFER) modified by liquid crystalline p-phenylene di[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as a curing agent, were studied by non-isothermal differential
scanning calorimetry (DSC) method. The relationship between apparent activation energy E
a and the conversion α was obtained by the isoconversional method of Ozawa. The reaction molecular mechanism was proposed. The results show that
the values of E
a in the initial stage are higher than other time, and E
a tend to decrease slightly with the reaction processing. There is a phase separation in the cure process with LC phase formation.
These curing reactions can be described by the Šesták–Berggren (S–B) equation, the kinetic equation of cure reaction as follows:
\frac\textda\textdt = Aexp( - \fracE\texta RT )am ( 1 - a )n {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = A\exp \left( { - {\frac{{E_{\text{a}} }}{RT}}} \right)\alpha^{m} \left( {1 - a} \right)^{n} . 相似文献
18.
P. N. Pathak Neelam Kumari D. R. Prabhu V. K. Manchanda 《Journal of solution chemistry》2012,41(3):410-421
Spectrophotometric investigations have been carried out on the disproportionation of Np(V) to form Np(IV) and Np(VI) in 1.1
mol⋅L−1 solutions of tributyl phosphate (TBP) and in N,N-dihexyl octanamide (DHOA) in n-dodecane medium. The Np(V) was found to coordinate with Np(IV) in 1.1 mol⋅L−1 TBP solution in n-dodecane to form a mixed valence “cation–cation” complex by bonding through an axial oxo group on Np(V). By contrast, this
interaction was less prominent in the case of 1.1 mol⋅L−1 DHOA solutions. The effect of 1-octanol, added as phase modifier, on the disproportionation behavior of Np(V) was also investigated.
An attempt was made to calculate the disproportionation/reduction rate constants for Np(V) under the conditions of these studies.
Absorbance measurements on the Np stripped from organic phases revealed the occurrence of Np(V) in the aqueous phase. 相似文献
19.
U. S. Makhmudov Sh. B. Rakhimov B. Tashkhodzhaev M. G. Levkovich V. I. Vinogradova 《Chemistry of Natural Compounds》2008,44(2):208-212
The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found
that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008. 相似文献
20.
Ramos CI Santana Marques MG Correia AJ Serra VV Tomé JP Tomé AC Neves MG Cavaleiro JA 《Journal of the American Society for Mass Spectrometry》2007,18(4):762-768
Reductions involving more than one electron with formation of the M+ and [M+2H]+ ions were observed for electrosprayed meso-tris(N-methylpyridinium-4-yl)porphyrin iodides, MI3. These reductions were studied by using different solvents and flow rates. Formation of the [M+2H]+ ions occurred only for protic solvents and to a larger extent at lower flow rates. The type of the fourth substituent does
not seem to affect the reduction processes. Formation of the two reduced species, M+ and [M+2H]+ ions, may occur through the participation of counter ion/solvent clusters. Reduction of multiply charged, non-metallated
species with formation of [M+nH]+ ions (n>1) was not observed before in positive mode electrospray mass spectrometry. 相似文献