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1.
Interaction of lithium cyclopentadienide with a suitable partially protected alpha-D-allofuranose triflate, 4, epimer at C3 of glucose, gives as a major product, besides the expected glucose-cyclopentadiene, 5, a glucose-disubstituted cyclopentadiene, 6. This unprecedented behaviour, which does not occur with alpha-D-glucofuranose and other sugars, is tentatively explained by a complexation of LiCp and the oxygen atoms of the isopropylidene function of one molecule of 4 and one of 5, giving a termolecular structure as the result of a template effect. The results of other experiments, such as the use of MgCp2 in place of LiCp or the complexation of oxygen atoms by lithium triflate, which changed the selectivity of the reaction largely in favour of the monosubstitution product 5, support this hypothesis. When lithium indenide is reacted with 4, glucose-monosubstituted and glucose-disubstituted indenes, 8 and 9, respectively, are formed, and 9 is obtained with almost total diastereoselectivity. This result can also be rationalised by a stereoselective complexation of lithium, as shown by separate experiments and by molecular mechanics calculations. Methyltricarbonyl molybdenum(II) complexes have been synthesised and characterised from glucose-monosubstituted 5 and glucose-disubstituted 6 cyclopentadienes. 相似文献
2.
Torvinen M Kalenius E Sansone F Casnati A Jänis J 《Journal of mass spectrometry : JMS》2011,46(8):787-793
The noncovalent complexation of three glucosylcalix[4]arenes (1-3) towards 23 mono- and dicarboxylic acid anions were studied by ESI-FTICR mass spectrometry. Competitive complexation, collision-induced dissociation and gas-phase H/D-exchange experiments were performed to obtain information on selectivity of calixarenes towards carboxylates and characteristics of their complexes. The flexibility and number of glucose units of the host and the spatial disposition of the hydrogen bonding groups on the carboxylate guests were found to affect the selectivity of complexation strongly. The glucosylcalixarenes exhibited particular selectivity for dicarboxylic acid anions incorporating π-systems, and clear isomeric selectivity was observed for isophthalic among phthalic acid anions and for fumaric acid over maleic acid anion. 相似文献
3.
环糊精聚合物与苯醌的分子包合作用及其在酶电极中的应用 总被引:1,自引:1,他引:0
研究了水溶性环糊精预聚合物的存在对苯醌/氢醌体系在铂电极上氧化还原行为的影响, 根据伏安曲线讨论了该预聚合物与苯醌的分子包合作用。环糊精预聚合物与戊二醛缩聚反应而形成的不溶性聚合物膜用于葡萄糖氧化酶的固定化, 以制得新型的第二代葡萄糖电极。由于分子包合作用, 作为电子受体的苯醌在含酶的环糊精聚合物膜中具有较高的浓度, 从而加速了固定化酶的电子传递。测定了酶电极上BQ反应的动力学参数。 相似文献
4.
Time-dependent complexation of glucose-reduced gold nanoparticles with octadecylamine Langmuir monolayers 总被引:3,自引:0,他引:3
Mayya KM Jain N Gole A Langevin D Sastry M 《Journal of colloid and interface science》2004,270(1):133-139
We report on the reduction of aqueous chloroaurate ions by glucose to form gold nanoparticles of uniform size. We further demonstrate the complexation of these particles with octadecylamine (ODA) monolayers at the air-water interface. Pressure-area (pi-A) isotherms as a function of time of complexation revealed a significant expansion of the monolayer. Surface pressure variation with time for constant areas after spreading of the monolayer was carried out to observe the kinetics of complexation of the colloidal particles at the interface. The kinetics of complexation of the particles at the interface was also monitored by Brewster angle microscopy (BAM) measurements. Langmuir-Blodgett films of the particles complexed with ODA were formed at a subphase pH of 9 onto different substrates. Quartz crystal microgravimetry (QCM) was used to quantify the amount of particles deposited per immersion cycle of the quartz crystal. The LB films were further characterized by UV-vis and transmission electron microscopy (TEM) measurements. TEM measurements indicate a close packed and equidistant arrangement of colloidal particles in the LB film, probably due to hydrogen-bonding interactions. 相似文献
5.
Markuszewski MJ Britz-McKibbin P Terabe S Matsuda K Nishioka T 《Journal of chromatography. A》2003,989(2):293-301
With a growing interest in new areas of bioanalytical research such as metabolome analysis, the development of sensitive capillary electrophoresis (CE) methods to analyze sub-microM concentrations of analytes in biological samples is required. In this report, the application of CE with sweeping by borate complexation is used to analyze a group of seven pyridine and adenine nucleotide metabolites derived from bacteria Bacillus subtilis cell extracts. Nanomolar (nM) detectability of analytes by CE with UV photometric detection is achieved through effective focusing of large sample plug (approximately 10% of capillary length) using sweeping by borate complexation method, reflected by a limit of detections (S/N = 3) of about 2 x 10(-8) M. Changes in metabolites concentrations were observed in cell extracts when using either glucose or malate as the carbon source in the culture medium. Concentration of pyridine and adenine nucleotides in cell extracts varied widely from 78.6 (+/-7.6) microM for nicotinamide-adenine dinucleotide in malate to 0.66 (+/-0.12) microM for nicotinamide-adenine dinucleotide phosphate in glucose culture medium. Concentrations of metabolites in a single cell were also estimated at millimolar (mM) level. The method was validated in terms of linearity, sensitivity and reproducibility. The application of CE by sweeping borate complexation allows for sensitive and reproducible analyses of nucleotide metabolites in complex biological samples such as bacteria cell extracts. 相似文献
6.
Cai W Wang GT Du P Wang RX Jiang XK Li ZT 《Journal of the American Chemical Society》2008,130(40):13450-13459
This paper reports a systematic study of the dynamic process for the self-assembly of chiral organogels from achiral hydrogen bonded hydrazide foldamers by induction of chiral glucose. Six foldamers incorporated with six decyl chains and two benzene, naphthalene, anthracene, or pyrene units at the ends are revealed to strongly gelate apolar and polar solvents, including alkanes, arenes, esters, alcohols, and 1,4-dioxane. The gels are characterized by UV-vis, fluorescent, XRD, SEM, and AFM methods, based on which a dislocated "tail-to-tail" stacking pattern is proposed. Addition of octylated glucose considerably enhances the capacity of the foldamers to gelate apolar solvents due to strong complexation. The complexation also causes unique dynamic helicity induction in the gels, which is studied systematically by circular dichroism. The results are treated with the Avrami theory according to a reported method (J. Am. Chem. Soc. 2005, 127, 4336), which suggests that the gelation involves a nucleation-elongation mechanism. In addition, the "Sergeants and Soldiers" effect in the gel phase is also revealed. 相似文献
7.
Gopikishore Valluru Hisham F. Sleem Florent Perret Imed Montasser Antoine Grandvoinnet 《Supramolecular chemistry》2014,26(7-8):561-568
The plasmon resonances of sulphonato-calixnaphthalene-capped silver nanoparticles have been used to study the complexation of the nanoparticles with nucleobases and amino acids. Only in the case of the nanoparticles capped with oxacalix[4]naphthalenesultone, does complexation of both nucleobases and certain amino acids occur. The complexation of the aromatic amino acids, phenylalanine and tryptophan, has previously not been observed for calixarene-capped silver nanoparticles. 相似文献
8.
环糊精聚合物的分子包合作用及在酶电极中的应用 总被引:10,自引:0,他引:10
伏安法用于研究环糊精预聚合物的分子包合作用.红外光谱实验表明环糊精预聚合物与戊二醛缩聚生成的聚合物带有悬挂的羰基,后者能使葡萄糖氧化酶共价固定化.由于分子包合作用,电子受体可存储在含酶的环糊精聚合物膜中,从而提高了酶膜中电子受体的浓度又减少了电子受体的用量.用TTF等作电子受体,可实现酶和电子受体在环糊精聚合物中的同时固定化.环糊精聚合物膜中的组成和膜厚度可以控制,为酶电极的基础研究工作提供了方便. 相似文献
9.
Dr. Sophie R. Beeren Dr. Sebastian Meier Prof. Ole Hindsgaul 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16314-16320
Branched starch polysaccharides are capable of binding multiple hydrophobic guests, but their exploitation as multivalent hosts and in functional materials is limited by their structural complexity and diversity. Linear α(1–4)‐linked glucose oligosaccharides are known to bind hydrophobic guests inside left‐handed single helices in solution and the solid state. Here, we describe the development of an amphiphilic probe that binds to linear α(1–4)‐linked glucose oligosaccharides and undergoes a conformational switch upon complexation, which gives rise to dramatic changes in the 1H NMR spectrum of the probe. We use this probe to explore hydrophobic binding sites in the branched starch polysaccharides amylopectin and β‐limit dextrin. Diffusion‐ordered (DOSY), nuclear Overhauser effect (NOESY) and chemical shift perturbation (HSQC) NMR experiments are utilised to provide evidence that, in aqueous solution, branched polysaccharides bind hydrophobic guests in well‐defined helical binding sites, similar to those reported for complexation by linear oligosaccharides. By examining the binding affinity of the probe to systematically enzymatically degraded polysaccharides, we deduce that the binding sites for hydrophobic guests can be located on internal as well as external branches and that proximal α(1–6)‐linked branch points weaken but do not prevent complexation. 相似文献
10.
Oshovsky GV Verboom W Fokkens RH Reinhoudt DN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(11):2739-2748
A series of saccharide-thiourea functionalized cavitands was prepared in good yields (72-86 %) by reaction of a tetrakis(aminomethyl) cavitand with the thiocyanate derivatives of acetylated glucose, galactose, and cellobiose. The anion complexation behavior of the acetylated and deacetylated glycocluster thioureamethyl cavitands was studied with electrospray ionization mass spectrometry (ESI-MS) in acetonitrile and in a 1:1 acetonitrile/water mixture, respectively. All compounds show a preference for Cl(-). A linear relationship was found between the square root of the intensity and the concentration of the formed host-guest complex. Based on this relationship, novel methods have been developed to determine K(a) values, by means of direct titration and competition experiments. 相似文献
11.
Philip W. Howard G. Richard Stephenson
Stephen C. Taylor
《Journal of organometallic chemistry》1989,370(1-3):97-109Homochiral 6-methoxy-substituted dienyltricarbonyliron complexes have been obtained from 1-methylcyclohexa-1,3-diene-5,6-diol (available via microbial oxidation of toluene) by complexation and removal of an allylic substituent with acids or with triphenylcarbenium tetrafluoroborate. A variety of optically active tricarbonyliron complexes have been produced from these compounds. The optical purity of the product and the stereochemistry of the complexation reaction have been determined. The high efficiency of chirality transfer during complexation of 5,6-dimethoxy-substituted dienes makes this method suitable as a general route to resolved organoiron complexes. 相似文献
12.
The cation complexation force of 18-crown-6 has been measured in ethanol by means of atomic force microscopy using probe tips and mica substrates modified chemically with 18-crown-6 and ammonium ion, respectively. The specific complexation force was suppressed by free potassium ion in the measurement solution, indicating a blocking effect based on the competitive complexation of the 18-crown-6 moiety between the free ion and the ammonium ion bound to the substrate. The single complexation force of 18-crown-6 with ammonium ion was evaluated to be about 60 pN in ethanol by autocorrelation analyses of the histograms for observed forces. 相似文献
13.
《Analytical letters》2012,45(10):1915-1927
Abstract An improved ASV-titration technique has been developed for estimating the complexation capacity of natural waters. In order to accomodate the slow kinetics of formation of certain complexes in water, an equilibration period of at least 24 hours is recommended. The use of copper as reference metal is recommended to obtain novel conservative estimates of complexation capacities. The method has been successfully applied to quantify complexation capacities of laboratory tap water and river waters. 相似文献
14.
The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been
examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out
in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation
reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature
on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation
reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration
graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated.
The text was submitted by the authors in English. 相似文献
15.
A spectrophotometric determination of ketoprofen based upon oxime formation followed by charge transfer complexation with o-chloranil has been developed. Different variables affecting the complexation process have been studied. Beer's law is obeyed in the concentration range 10-80 microg/ml. The method has been successfully applied to the determination of ketoprofen in pure form and in pharmaceutical dosage forms in the presence of its impurities. 相似文献
16.
17.
Heterocomplexation of a chiral host to a racemic guest has been discovered. A cyclic dipeptide generated from (S)-proline alkyl ester undergoes an achiroselective complexation to both the enantiomers of racemic BINOL in benzene to yield a crystalline heterocomplex bearing the solvent molecules. However, complexation crystallization does not occur between the diptide and either enantiomer of BINOL under similar conditions. The difference in complexation behavior has been successfully applied in the enantiomeric enrichment of nonracemic BINOLs, and almost quantitative separation of the excess enantiomer from racemic BINOL was achieved. 相似文献
18.
19.
Gas-liquid chromatography was applied in thermodynamic investigations of processes of complexation and enantioseparation by alpha- and [-cyclodextrins of chiral monoterpenoids. The distribution constants, stability constants and thermodynamic parameters enthalpy, entropy and free energy of the complexation processes were determined. It has been found that enantioseparation of monoterpenes by alpha- and beta-cyclodextrins is the result of formation of 1:2 stoichiometric complexes. When 1:1 stoichiometric complexes are formed, enantioselectivity is not observed. All investigated processes of complexation are enthalpy-driven regardless of the stoichiometry of the formed complexes. -deltaH, -TdeltaS and -deltaG of complexation process have higher values for bicyclic than for monocyclic monoterpenoids as well as for alpha-CD than for beta-CD. The first or second step of complexation may be responsible for enantioselectivity. 相似文献
20.
Four novel cyclotriveratrylene (CTV) derivatives with three benzoate pendants bearing different aliphatic chains have been prepared in good yields, starting from CTV. The complexation behavior of these CTV derivatives towards C60 in arene solvents has been measured by UV‐visible spectroscopy and high complexation constants are obtained. It is observed that the complexation is promoted pronouncedly by introducing methyl ester groups to the aromatic pendants, while this promoting effect is reduced when the methyl groups are replaced by longer alkyl groups. 相似文献