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At least 937 records · Page 52Linked to original sources
PubMed2000

Structure of an atypical O-antigen polysaccharide of Helicobacter pylori containing a novel monosaccharide 3-C-methyl-D-mannose.

Lipopolysaccharides (LPS) were isolated by hot phenol-water extraction from Danish Helicobacter pylori strains D1, D3, and D6, which were nontypeable using a variety of anti-Lewis and anti-blood-group monoclonal antibodies. An atypical O-chain polysaccharide (PS) was liberated from the LPS of the three strains by acid under mild conditions and found to contain D-rhamnose (D-Rha), L-rhamnose (L-Rha), and a branched sugar, 3-C-methyl-D-mannose (D-Man3CMe). The last sugar, which has not hitherto been found in Nature, was identified using GLC-MS of the derived alditol acetate and the partially methylated alditol acetate, and (1)H and (13)C NMR spectroscopy, including NOESY and (1)H,(13)C HMBC experiments. The following structure of the trisaccharide repeating unit of the PS was established: -->2)-alpha-D-Manp3CMe-(1-->3)-alpha-L-Rhap-(1-->3)-alpha-D- Rhap-(1-- >. In contrast to the pathogenic importance of the Lewis antigen mimicry exhibited by the PS of H. pylori strains previously investigated, the biological relevance of the atypical PS for H. pylori pathogenesis is unclear. The production of a differing surface PS may represent a form of antigenic variation by these particular H. pylori strains and/or may reflect the adaptation of these strains to a particular human population.

Acids↗
PubMed2004

A comparative analysis of localized and propagating surface plasmon resonance sensors: the binding of concanavalin a to a monosaccharide functionalized self-assembled monolayer.

A comparative analysis of the properties of two optical biosensor platforms: (1) the propagating surface plasmon resonance (SPR) sensor based on a planar, thin film gold surface and (2) the localized surface plasmon resonance (LSPR) sensor based on surface confined Ag nanoparticles fabricated by nanosphere lithography (NSL) are presented. The binding of Concanavalin A (ConA) to mannose-functionalized self-assembled monolayers (SAMs) was chosen to highlight the similarities and differences between the responses of the real-time angle shift SPR and wavelength shift LSPR biosensors. During the association phase in the real-time binding studies, both SPR and LSPR sensors exhibited qualitatively similar signal vs time curves. However, in the dissociation phase, the SPR sensor showed an approximately 5 times greater loss of signal than the LSPR sensor. A comprehensive set of nonspecific binding studies demonstrated that this signal difference was not the consequence of greater nonspecific binding to the LSPR sensor but rather a systematic function of the Ag nanoparticle's nanoscale structure. Ag nanoparticles with larger aspect ratios showed larger dissociation phase responses than those with smaller aspect ratios. A theoretical analysis based on finite element electrodynamics demonstrates that this results from the characteristic decay length of the electromagnetic fields surrounding Ag nanoparticles being of comparable dimensions to the ConA molecules. Finally, an elementary (2 x 1) multiplexed version of an LSPR carbohydrate sensing chip to probe the simultaneous binding of ConA to mannose and galactose-functionalized SAMs has been demonstrated.

Binding Sites↗
PubMed2004

NMR analysis of enzyme-catalyzed and free-equilibrium mutarotation kinetics of monosaccharides.

We have exploited the saturation difference (SD) NMR technique to investigate the mutarotations of two sugars, l-fucose and d-ribose, at equilibrium. The KM and kcat values of Escherichia coli FucU-catalyzed mutarotation of l-fucose have been determined by this technique, and the values of KM for alpha- and beta-forms are shown to be the same. Similarly, the spontaneous mutarotation of d-ribose was investigated by using the same method, and it was found that d-ribose has an exceptionally high spontaneous alpha-to-beta conversion rate only between the furan forms.

Carbohydrate Conformation↗
PubMed2000

Aldol addition of lithium and boron enolates of 1,3-dioxan-5-ones to aldehydes. A new entry into monosaccharide derivatives

Methods allowing control of stereoselectivity in aldol reactions of enolates derived from 1,3-dioxan-5-ones (4) are described. Boron enolates, generated in situ, react with benzaldehyde to give the corresponding anti aldol selectively (the anti:syn ratio of up to 96:4) and in high yield. Lithium enolates give high anti selectivity only with aldehydes branched at the alpha-position. Enantioselective deprotonation of C(S) symmetrical dioxanones (e.g., 4b) can be accomplished efficiently, with enantiomeric excess of up to 90%, with chiral lithium amide bases of general structure PhCH(Me)N(Li)R (9, 10) if the R group is sufficiently bulky (e.g, R = adamantyl) or is fluorinated (e.g., R = CH2CF3). Dioxanone boron and lithium enolates react readily with glyceraldehyde derivatives (19), yielding protected ketohexoses (20 and 21).

Journal Article↗
PubMed1998

Development of glycosylated human interleukin-1alpha, neoglyco IL-1alpha, by coupling with D-galactose monosaccharide: biological activities in vitro.

In the previous study, galactose with C9 spacer was chemically coupled to human recombinant (rh) IL-1alpha in order to study the effect of glycosylation on its activities, and to develop IL-1 with less deleterious effects. In this study we examined a variety of IL-1 activities in vitro, including proliferative effect on T cells, antiproliferative effect on myeloid leukemic cells and melanoma cells, stimulatory effects on IL-6 synthesis by melanoma cells and PGE2 synthesis by fibroblast cells Galactose-introduced IL-1alpha (Gal-IL-1alpha) exhibited reduced activities from 10 to 10000 times compared with unmodified IL-1alpha in all the activities performed in vitro. The competitive binding of 125I-IL-1alpha to mouse T cells and pre-B cells with unlabeled IL-1alpha s suggests a decrease in binding affinities of Gal-IL-1alpha to both type I and type II IL-1 receptors. Therefore, reduced activities of Gal-IL-1alpha are due, at least partially, to the decrease in their receptor binding affinities.

Animals↗
PubMed2001

New artificial siderophores based on a monosaccharide scaffold.

New artificial catecholate siderophores with methyl alpha-D-glucopyranoside as scaffold were synthesized. The dihydroxy- or di(acetoxy)benzoyl moieties were attached either directly or via aminopropyl spacer groups, to the carbohydrate scaffold. The siderophore activity of the prepared siderophore analogs was examined by a growth promotion assay using various Gram-negative bacteria and mycobacteria and by the CAS-assay.

Gram-Negative Bacteria↗
PubMed2004

Ophthalmic glucose sensing: a novel monosaccharide sensing disposable and colorless contact lens.

We have developed a technology for continuous tear glucose monitoring, and therefore potentially blood glucose monitoring, using a daily use, disposable contact lens embedded with sugar-sensing boronic acid containing fluorophores. The novelty of our approach is two fold. Firstly, the notion of sensing extremely low glucose concentrations in tears by our approach, and secondly, the unique compatibility of our new probes with the internal environment of the disposable, off-the-shelf, contact lenses, chosen because the physiological compatibility of disposable plastic contact lenses has already been assessed and optimized with regard to vision correction, size and oxygen/analyte permeability. Our findings show that our approach is indeed suitable for the continuous monitoring of tear glucose levels in the concentration range (50-500 microM), which track blood glucose levels which are approximately 5-10 fold higher. We believe our approach offers unique opportunities for non-invasive continuous glucose monitoring for diabetics, especially since many have eye disorders and require vision correction by either contact lenses or glasses, which is thought to be due to glycation of protein in blood vessels.

Boronic Acids↗
PubMed1980

Permeability of lactating-rat mammary gland Golgi membranes to monosaccharides.

The Golgi-membrane vesicles present in particulate preparations of lactating rat mammary gland were biosynthetically loaded with [14C]lactose. This lactose was effectively retained by particles sedimented after exposure to 0.25 M-disaccharide, but was partly lost after exposure to 0.25 M-glucose or other solutes of similar size. Loss of lactose was time-, concentration- and temperature-dependent and varied with the solute structure. This behaviour is ascribed to the presence of protein in the Golgi membrane, forming a specific carrier or channel that serves to supply glucose for lactose synthesis.

Animals↗
PubMed1984

Monosaccharide transport in the mammary gland of the intact lactating rat.

The Michaelis-Menten equation for the utilization of competing substrates was applied to the uptake of 2-deoxy[3H]glucose into the mammary gland of anaesthetized lactating rats. Intracellular water was calculated from total tissue water and sucrose space. Fed rats had a mean transport capacity of 2.2 mumol/min per g of tissue, giving an actual glucose transport in vivo of 1.1 mumol/min per g. Transport decreased by 90% on overnight starvation and returned to normal by 2 h of re-feeding. Similar changes were observed in the 1 min or 5 min transport of circulating 3-O-methylglucose. Transport of 3-O-methylglucose in starved rats was restored towards normal by insulin. In fed rats it increased between parturition and day 12 of lactation. The findings support the proposal that transport is a rate-limiting factor in the mammary utilization of carbohydrate.

3-O-Methylglucose↗
PubMed1990

1H-n.m.r. investigation of naturally occurring and chemically oversulphated dermatan sulphates. Identification of minor monosaccharide residues.

The 1H-n.m.r. spectra of various dermatan sulphate preparations present, besides the major signals of the basic disaccharide unit, several other minor signals. We have assigned most of them by n.m.r., using two-dimensional proton-proton double-quantum-correlation and nuclear-Overhauser-effect spectroscopy experiments. This allowed us to identify 2-O-sulphated L-iduronic acid and D-glucuronic acid residues as well as 6-sulphated N-acetylgalactosamine (presumably 4-O-sulphated as well). 2-O-Sulphated iduronic acid was present to similar extents (6-10% of total uronic acids) in pig skin dermatan sulphate and pig intestine dermatan sulphate, whereas glucuronic acid represented 17% of the uronic acid of pig skin dermatan sulphate and was virtually absent (1%) from the other preparation. 6-O-Sulphated N-acetylgalactosamine was present in minor amounts in pig intestine dermatan sulphate only. The influence of sulphation of iduronic acid units on their conformation was assessed by using chemically oversulphated pig intestine dermatan sulphate. Introduction of sulphate groups in this unit in dermatan sulphate tends to shift the conformational equilibrium towards the 1C4 conformer.

Animals↗
PubMed2002

Glycemic, hormone, and appetite responses to monosaccharide ingestion in patients with type 2 diabetes.

To investigate the relative effects of fructose and glucose on blood glucose, plasma insulin and incretin (glucagon-like peptide-1 [GLP-1] and gastric inhibitory peptide [GIP]) concentrations, and acute food intake, 10 (6 men, 4 women) patients with diet-controlled type 2 diabetes (diabetic) (44 to 71 years) and 10 age and body mass index (BMI)-matched (6 men, 4 women) nondiabetic, control subjects with varying degrees of glucose tolerance (nondiabetic), were studied on 3 days. In random order, they drank equienergetic preloads of glucose (75 g) (GLUC), fructose (75 g) (FRUCT) or vehicle (300 mL water with noncaloric flavoring [VEH]) 3 hours before an ad libitum buffet lunch. Mean glucose concentrations were lower after FRUCT than GLUC in both type 2 diabetics (FRUCT v GLUC: 7.5 +/- 0.3 v 10.8 +/- 0.4 mmol/L, P <.001) and nondiabetics (FRUCT v GLUC: 5.9 +/- 0.2 v 7.2 +/- 0.3 mmol/L, P <.05). Mean insulin concentrations were approximately 50% higher after FRUCT in type 2 diabetics than in nondiabetics (diabetics v nondiabetics: 23.1 +/- 0.7 v 15.1 +/- 1.3 microU/mL; P <.0001). Plasma GLP-1 concentrations after fructose were not different between type 2 diabetics and nondiabetics (P >.05). Glucose, but not FRUC, increased GIP concentrations, which were not different between type 2 diabetics and nondiabetics (P >.05). Food intake was suppressed 14% by GLUC (P <.05 v CONT) and 14% by FRUC (P <.05 v CONT), with no difference between the amount of food consumed after GLUC and FRUC treatment in either type 2 diabetics or nondiabetics (P >.05). We have confirmed that oral fructose ingestion produces a lower postprandial blood glucose response than equienergetic glucose and demonstrated that (1) fructose produces greater increases in plasma insulin concentration in type 2 diabetics than nondiabetics, not apparently due to greater plasma incretin concentrations and (2) fructose and glucose have equivalent short-term satiating efficiency in both type 2 diabetics and nondiabetics. We conclude that on the basis of improved glycemic control, but not satiating efficiency, fructose may be useful as a replacement for glucose in the diet of obese patients with type 2 diabetes.

Adult↗