Postcolumn HPLC detection of mono- and oligosaccharides with a chemosensor

Novel chromophoric compound 1 promotes the HPLC postcolumn detection of mono- and oligosaccharides. The detection of chromatographic peaks in the visible region for glucose, fructose, maltodextrins, sialic acid, and a ganglioside can be accomplished with a standard UV-vis detector. The use of selective, reversible binding agents in automated HPLC assays should allow for improved monitoring of specific analytes as well as material recovery. [structure: see text]     

Selective formation of heterodimeric resorcinarene capsules

C_2V-symmetrical resorcinarene tetraesters 1 form in CDCl₃ dimeric capsules encapsulating one Me₄N⁺ cation. The homodimeric capsules of the tetra(3,4,5-trimethoxybenzoate) 1d and tetrabenzoate 1b or tetrafuroylate 1c disproportionate in solution to give quantitatively the heterodimers. The higher stability of the heterodimer is, most probably, caused by π-π attractions between the π-basic trimethoxyphenyl rings of 1d and relatively more π-accepting phenyl or furyl fragments of 1b or 1c.     

Selective oxidative debenzylation of mono- and oligosaccharides in the presence of azides

When using benzyl ethers as permanent protecting groups in oligosaccharide synthesis selective oxidative debenzylation with NaBrO(3) + Na(2)S(2)O(4) under biphasic conditions is efficient and compatible with anomeric azides and many other functions.     

Optimization of the capillary gas chromatographic analysis of mono- and oligosaccharides in honeys

Summary A capillary gas chromatographic method has been developed for simultaneous determination of at least 18 sugars (2 monosaccharides, 11 disaccharides and 5 trisaccharides) in honey, as their oxime-trimethylsilyl ethers. The chromatographic conditions have been systematically and thoroughly optimized, to eliminate the peak overlap commonly reported for this and other methods, especially for disaccharides. Complete analytical details are reported.     

Study of the nmr spectra of mono- and oligosaccharides in the region of a strong magnetic field

Conclusions An investigation of the NMR spectra of mono- and oligosaccharides in the region of a strong magnetic field permits a judgment of the conformational and configurational changes in the structure of monosaccharides, as well as the order and conformation of the bonds between monosaceharide residues in oligosaccharides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1854–1856, August, 1969.     

Oligosaccharide profiling: the facile detection of mono-, di- and oligosaccharides by electrospray orthogonal time-of-flight mass spectrometry using 3-aminophenylboronic acid derivatization

Monosaccharides, disaccharides and larger carbohydrates can be derivatized using 3-aminophenylboronic acid (3-APBA). This procedure is carried out at low pH (2.7-3.0) and allows the use of positive ion mode electrospray orthogonal time-of-flight mass spectrometry (ES-OTOFMS) to analyze the resulting boronate complexes. A carbohydrate profile map of a complex carbohydrate mixture, honey, was prepared which displayed superior sensitivity when compared with lithium ion cationization. Complexes formed using simple mono- and disaccharides show that facile in situ derivatization leads to an equilibrium mixture; which is reproducible for a specific set of electrospray conditions. D-Glucose could be detected at 5 microM concentration using the standard instrument spray interface. Lower detection levels of approximately 500 nM could be achieved using a nanospray device. The 3-APBA complexes are observed on instruments employing a low temperature interface (140-150 degrees C) which allows formation of the boronate species while still promoting efficient desolvation of the ions. The spectral identification of 3-APBA complexed carbohydrates in complex mixtures is facilitated by the easily observed 1 mass unit separated peak pair bearing the 1:4 ratio resulting from the natural isotopic abundance of (10)B and (11)B.     

Depolarization thermocurrents in frozen aqueous solutions of mono- and di-saccharides

The dielectric behaviour of frozen aqueous solutions of the monosaccharides glucose, galactose, mannose, ribose and arabinose and the disaccharides cellobiose, lactose and maltose was studied by the depolarization thermocurrent (DTC) method in the temperature range 80–270 K and over a wide range of concentrations (0.0003–1.5 mol/l), to obtain information on the state of water in the solutions. The results show that the saccharides studied can be subdivided into two classes regarding their hydration behaviour. The solutions of glucose, galactose and mannose are characterized by a continuous transition from hydration (i.e. affected by the solute molecule) to free (i.e. non-affected) H₂O molecules. The solutions of ribose, arabinose, cellobiose, lactose and maltose are characterized by the presence of two dicrete kinds of H₂O molecules, namely free and hydration molecules. These results are discussed in terms of a hydration model.     

Pre-organized oligomodified resorcinarene ligands. Preparation,structure, and complex formation

Interaction of various conformations of resorcinarenes with carbamoyl chloride, thiocarbamoyl chloride, and trifluoromethanesulfonic acid anhydride has resulted in a series of derivatives with certain pre-organization of the macrocyclic scaffold and the immobilized electron-donating groups. Complex formation of the selected prepared compounds towards Pd(II) derivatives has been studied.     

The formation of mono- and bimetallic silver-containing seed nanoparticles

The regularities of the formation of mono- and bimetallic seed particles used for subsequent synthesis of anisotropic silver nanoparticles in micellar media has been studied. It has been found that the formation of nanosized silver seed particles is influenced by the synthesis parameters, such as the presence of oxygen and gold in the reaction system. Based on characteristics of the surface plasmon resonance band of nanoparticles, a simple and efficient method has been proposed for controlling the degree of monodispersity of the seed particles.     

Mechanisms of ion formation in field desorption of oligosaccharides

Energy deficits have been measured for ions in the field desorption mass spectra of saccharides. Evidence is presented to show that monosaccharides, disaccharides and trisaccharides are volatile compounds, under the conditions of field desorption. It is proposed that the electric field plays an essential role in the desorption of [M+H]⁺ ions.     

Laser flash photolysis detection of mono- and biradical mesitylene

Time-resolved transient absorption spectra have been obtained first for mesitylene by 355 nm laser flash photolysis at ambient temperature. Mono- and biradicals were observed in the experiment, in which the transient absorption peak at about 370 nm was assigned to the biradical and the peak at about 580 nm to the monoradical; the biradical has a longer lifetime than the monoradical. According to the representative value of the C-H bond dissociation energy for aromatic compounds monoradical formation might be a single-photon process. For comparison with the absorption spectra the time-resolved fluorescence spectra were obtained and also the biradical was assigned to about 393 nm.     

Adduct formation of methyltrioxorhenium with mono- and bidentate nitrogen donors: formation constants

The coordination of N-donor ligands to MTO (methyltrioxorhenium) is governed by both electronic and steric effects. For example, the binding constant of pyridine to MTO is 196.6 L mol(-)(1), whereas that of the better donor 4-picoline is 732 L mol(-)(1) and that of the sterically encumbered 2,6-di-tert-butyl-4-methylpyridine is <1 L mol(-)(1). Equilibrium constants have been evaluated for this reaction, MTO + L = MTO.L, where L comprises mono- and bidentate N-donor ligands. The values of log K for monodentate ligands range from <0 for 2-substituted pyridines to 3.3 for 1-butylimidazole and for bidentate ligands from 2.2 for 2,2'-bipyridine to 5.27 for 4,7-dimethyl-1,10-phenanthroline at 25 degrees C in chloroform. A successful correlation of log K with pK(a) of L was realized except in the case of 2-substituted ligands, where steric effects make K smaller than expected from the proton basicity of L.     

A simple visual method for DNA detection based on the formation of gold nanoparticles

A simple visual method for DNA detection during the formation of gold nanoparticles (AuNPs) was developed based on different electrostatic properties of single strand DNA (ssDNA) and double strand DNA (dsDNA). It could identify target DNA in 10 min.     

A simple visual method for DNA detection based on the formation of gold nanoparticles

A simple visual method for DNA detection during the formation of gold nanoparticles (AuNPs) was developed based on different electrostatic properties of single strand DNA (ssDNA) and double strand DNA (dsDNA). Since the ssDNA is easy to bind to AuNPs due to its exposed bases which could prevent salt-induced aggregation of AuNPs. The dsDNA always present negative charge because its negatively charged phosphate backbone is exposed. In this case, the dsDNA could disturb the adsorption between dsDNA and AuNPs and result in non-aggregation of AuNPs. After hybridization, chloroauric acid and ascorbic acid were added to the mixture solution, and the solution changed to red immediately and turned to purple in 10 min in the present of target DNA. TEM results confirmed that the change of color stemed from aggregation of AuNPs. In order to obtain accurate results by naked eye, the DNA detection assay should be conducted under pH 7.0.     

Laser flash photolysis detection of mono- and biradical mesitylene

Time-resolved transient absorption spectra have been obtained first for mesitylene by 355 nm laser flash photolysis at ambient temperature. Mono- and biradicals were observed in the experiment, in which the transient absorption peak at about 370 nm was assigned to the biradical and the peak at about 580 nm to the monoradical; the biradical has a longer lifetime than the monoradical. According to the representative value of the C—H bond dissociation energy for aromatic compounds monoradical formation might be a single-photon process. For comparison with the absorption spectra the time-resolved fluorescence spectra were obtained and also the biradical was assigned to about 393 nm.     

Spontaneous formation of hexameric resorcinarene capsule in chloroform solution as detected by diffusion NMR

NMR diffusion measurements provide unequivocal proof that the resorcinarene 1b self-assembles spontaneously into a stable hexamer capsule in chloroform solution by encapsulating several chloroform molecules, which occupy different chemical positions. Although the affinity of tetrahexylammonium bromide (2a) toward the cavity of the hexamer is much higher than that of the chloroform molecules, it was found that the same amount of DMSO is needed to disrupt the two hexamers, thus suggesting similar stabilities for these two supramolecular capsules.     

Simulation of equilibria of formation of mono- and polynuclear heteroligand cobalt(II) and nickel(II) complexonates in aqueous solutions

We report the results of our studies of the protolytic and coordination equilibria of formation of mono- and polynuclear heteroligand complexonates containing cobalt(II) and nickel(II) salts and EDTA, as well as monoamine complexons, such as iminodiacetic acid and hydroxyethyliminodiacetic acid. The experimental data obtained by absorption spectrophotometry were processed using the mathematical models that allowed us to assess the probability of existence of a broad range of complex species in the solution and to select the species sufficient for the experimental data to be reconstituted from them. The compositions of the polynuclear heteroligand cobalt(II) and nickel(II) complexonates were determined. The pH ranges of their existence were found; the equilibrium constants of the reactions and the stability constants of the resulting complexes were calculated. An assumption is made about their structure.