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At least 829 records · Page 46Linked to original sources
PubMed1987

High-performance liquid chromatographic separation of some mono- and disaccharides with detection by a post-column enzyme reactor and a chemically modified electrode.

The effluent from a chromatographic column was mixed with nicotinamide adenine dinucleotide coenzyme (NAD+) buffer and passed through a packed-bed reactor containing immobilized glucose dehydrogenase. Oxidation of the carbohydrates emerging from the column produced an equivalent amount of reduced coenzyme (NADH), which was detected electrochemically using an electrode modified with 7-dimethylamino-1,2-benzophenoxazine (Meldola Blue). Separation was effected in three different chromatographic systems containing a protonated ion exchanger, a calcium(II)-saturated or a lead(II)-saturated ligand exchange column. Separation, detection and k' values are reported for glucose, 2-deoxyglucose, xylose, mannose, cellobiose, lactose, ribose and glucosamine. The detection limit was 2 ng for a 20-microliter injection of glucose and the response was linear up to 6300 ng. Samples from fermentation of penicillin were analysed for lactose and glucose with the described detector. A comparison with the recordings from a refractive index detector showed that the selectivity of the enzymes and the modified electrodes are necessary for the determination of glucose and lactose.

Chromatography, High Pressure Liquid↗
PubMed2002

Hydroxyester disaccharides from fruits of cape gooseberry (Physalis peruviana).

The 3-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside of ethyl 3-hydroxyoctanoate and the diastereomeric 3-O-alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranosides of (3R) and (3S)-butyl 3-hydroxybutanoate, respectively, were isolated by chromatographic methods from fruits of cape gooseberry (Physalis peruviana) harvested in Colombia. Their structures were identified by ESI-MS/MS and NMR spectroscopy. The three glycoconjugates can be considered as immediate precursors of ethyl 3-hydroxyoctanoate and butyl 3-hydroxybutanoate, which are important aroma volatiles found in the fruit.

Disaccharides↗
PubMed1993

Conformations of disaccharides by empirical force field calculations. Part V: Conformational maps of beta-gentiobiose in an optimized consistent force field.

A recently optimized set of potential energy functions is used to investigate the conformational flexibility of the beta-(1-->6) glycosidic linkage in beta-gentiobiose. Relaxed Ramachandran maps in vacuo are presented in the torsional angles phi and omega, with torsional angle psi allowed to relax freely, as are all other internal degrees of freedom. The study reveals two almost iso-energetic low energy domains in (phi, psi, omega) space, and cross-sections in the low-energy domains at omega = -60 degrees and omega = 60 degrees show that more than 60% and 70% respectively of the area of the conformational maps are accessible within 40 kJ mol-1. The molecular structure in the crystal, including the exoanomeric effect, is well reproduced. The structure belongs to the potential energy well which includes the global potential energy minimum in vacuo. The most profound structural difference between the crystal structure and the calculated global minimum in vacuo is the 20 degrees deviation of the psi torsional angle (24 degrees from perfect trans). It occurs in the most flexible glucosidic degree of freedom, psi, and is caused by optimization of the hydrogen bonding network and not by the exoanomeric effect.

Carbohydrate Conformation↗
PubMed1980

Glucose oxidase bienzyme electrodes for ATP, NAD+, starch and disaccharides.

Based on a glucose oxidase sensor for determination of glucose several glucoseoxidase bioenzyme electrodes have been developed. Enzymes producing glucose by hydrolysis of saccharides (glucamylase, invertase, cellulase) as well as glucose consuming systems (hexo-kinase, glucose dehydrogenase) have been coupled to glucose oxidase. The function of the bienzyme systems was demonstrated by concentration measurements (blood glucose, maltose, ATP, NAD+, starch) and enzyme activity measurements (alpha-amylase, ATPase, lactate dehydrogenase).

Adenosine Triphosphate↗
PubMed1998

Disaccharides permeases: constituents of xylanolytic and mannanolytic systems of Aureobasidium pullulans.

Aureobasidium pullulans, a yeast-like microorganism was found to produce mannobiose permease and xylobiose permease, transporting beta-1,4-mannobiose or beta-1,4-xylobiose into the cells from extracellular media. Both permeases are induced by the same inducers as the corresponding hemicellulolytic enzyme systems. Mannobiose permease is induced by beta-1,4-mannobiose or is formed in the cells growing on mannan (inducers of beta-mannanolytic enzymes) and xylobiose permease is induced by d-xylose, beta-1,4-xylobiose or during the growth on xylan (inducers of xylanolytic enzymes). The permeases are energy dependent, synthesized de novo and their activities are inhibited by d-glucose. Since mannobiose permease transports beta-1,4-mannobiose, xylobiose permease appears to be less specific and transports beta-1,4-mannobiose, beta-1,4-xylobiose and methyl beta-d-xylopyranoside. Methyl beta-d-mannopyranoside or methyl beta-d-xylopyranoside serve as less efficient inducers of the corresponding permeases than beta-1,4-mannobiose or beta-1, 4-xylobiose.

Disaccharides↗