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PubMed1994

Thermodynamics of lectin-carbohydrate interactions. Titration microcalorimetry measurements of the binding of N-linked carbohydrates and ovalbumin to concanavalin A.

The thermodynamics of binding of concanavalin A (Con A) with a series of linear and branched chain oligosaccharides including certain N-linked complex type and oligomannose type carbohydrates and a fraction of quail ovalbumin containing Man7 and Man8 oligomannose chains have been determined using titration microcalorimetry. Methyl3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, a branch chain trisaccharide moiety found in all N-linked carbohydrates which possesses approximately 60-fold higher affinity than methyl alpha-D-mannopyranoside, exhibited a change in enthalpy of binding (delta H) of -14.4 kcal mol-1 as compared to -8.2 kcal mol-1 for the monosaccharide. This demonstrates that Con A possesses an extended binding site for the trimannoside. However, a biantennary complex type carbohydrate with terminal beta (1,2)-GlcNAc residues which binds with 3-fold higher affinity than the trimannoside possesses a delta H of only -10.6 kcal mol-1. A plot of -delta H versus -T delta S for the carbohydrates in the present study showed positive deviations in -T delta S for the complex type carbohydrate, as well as alpha (1,2)-di- and trimannosyl oligosaccharides which are part of the structures of oligomannose type carbohydrates. The relative favorable changes in binding entropies of these compounds are attributed to the presence of multiple internal and terminal residues in each molecule which can independently bind to the monosaccharide binding site of the lectin. The delta H values for the complex type carbohydrate and the alpha (1,2) mannose oligosaccharides were also approximately -2.5 kcal mol-1 greater than that of methyl alpha-D-mannopyranoside, indicating some extended binding site interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Complete structure of the cell surface polysaccharide of Streptococcus oralis ATCC 10557: a receptor for lectin-mediated interbacterial adherence.

Lectin-carbohydrate binding is known to play an important role in a number of different cell-cell interactions including those between certain species of oral streptococci and actinomyces that colonize teeth. The cell wall polysaccharides of Streptococcus oralis ATCC 10557, S. oralis 34, and Streptococcus mitis J22, although not identical antigenically, each function as a receptor molecule for the galactose and N-acetylgalactosamine reactive fimbrial lectins of Actinomyces viscosus and Actinomyces naeslundii. Carbohydrate analysis of the receptor polysaccharide isolated from S. oralis ATCC 10557 shows galactose (3 mol), glucose (1 mol), GalNAc (1 mol), and rhamnose (1 mol). 1H NMR spectra of the polysaccharide show that is is partially O-acetylated. Analysis of the 1H NMR spectrum of the de-O-acetylated polysaccharide shows that it is composed of repeating subunits containing six monosaccharides and that the subunits are joined by a phosphodiester linkage. The 1H and 13C NMR spectra were completely assigned by two-dimensional homonuclear correlation methods and by 1H-detected heteronuclear multiple-quantum correlation (1H[13C]HMQC). The linkage of the component monosaccharides in the polymer, deduced from two-dimensional 1H-detected heteronuclear multiple-bond correlation spectra (1H[13C]HMBC), shows that the repeating unit of the de-O-acetylated polymer is a linear hexasaccharide with no branch points. The complete 1H and 13C assignment of the native polysaccharide was carried out by the same techniques augmented by a 13C-coupled hybrid HMQC-COSY method, which is shown to be especially useful for carbohydrates in which strong coupling and overlapping peaks in the 1H spectrum pose difficulties. The fully assigned spectra of the native polymer show that each of two different positions is acetylated in one-third of the repeating subunits and that the acetylation is randomly distributed along the polymer. The exact positions of acetylation were assigned by a carbonyl-selective HMBC method that unambiguously defines the positions of O-acetylation. The complete structure of the native polysaccharide in S. oralis ATCC 10557 is [formula: see text] Comparison of this structure with those previously determined for the polysaccharides of strains 34 and J22 suggests that the similar lectin receptor activities of these molecules may depend on internal galactofuranose linked (beta 1----6)- to Gal(beta 1----3)GalNAc(alpha) or GalNAc(beta 1----3)Gal(alpha).

Acetylation↗
PubMed1988

Purification, composition, and structure of macrophage adhesion molecule.

Macrophage adhesion molecule (MAM) is a surface heterodimer consisting of the trypsin- and plasmin-sensitive glycopeptide gp160 (MAM-alpha) and the glycopeptide gp93 (MAM-beta). MAM, which is the guinea pig analogue of Mo1 and Mac-1, was purified from detergent lysates of peritoneal neutrophils by lentil lectin chromatography and M2-antibody chromatography. The pure heterodimer molecule was dissociated by acidic conditions (pH 3.5), and MAM-alpha and MAM-beta were separated by M7-antibody chromatography. MAM-beta is an approximately 640 amino acid residue polypeptide with exceptionally high cysteine content. At 7.2 residues per 100 amino acids, Cys/2 of MAM-beta is more than 3 times the mean for 200 purified proteins. Reactivity with six beta-subunit-specific monoclonal antibodies recognizing at least four epitopes demonstrated that intrapeptide disulfide bonds are required to maintain the structure of MAM-beta. All six antibodies failed to react when MAM-beta was treated with reducing agents. MAM-beta is 18% carbohydrate; the major monosaccharides are mannose, N-acetylglucosamine, galactose, and sialic acid. MAM-beta is estimated to contain five to six N-linked carbohydrate units. MAM-alpha is an approximately 1100-residue polypeptide with lower Cys/2 content (2.0 residues per 100 amino acid residues). MAM-alpha is 21% carbohydrate. The major monosaccharides are mannose, N-acetylglucosamine, galactose, and sialic acid; the mannose content is higher in MAM-alpha than MAM-beta. MAM-alpha is estimated to contain 12 N-linked carbohydrate units.

Amino Acids↗
PubMed1989

Binding characteristics of N-acetylglucosamine-specific lectin of the isolated chicken hepatocytes: similarities to mammalian hepatic galactose/N-acetylgalactosamine-specific lectin.

Binding characteristics of N-acetylglucosamine- (GlcNAc) specific lectin on the chicken hepatocyte surface were probed by an inhibition assay using various sugars and glycosides as inhibitors. Results indicated that the binding area of the lectin is small, interacting only with GlcNAc residues whose 3- and 4-OH's are open. The combining site is probably of trough-type, since substitution with as large a group as monosaccharide is permitted on the C-6 side of GlcNAc, and on the C-1 side, the aglycon of GlcNAc can be very large (e.g., a glycoprotein). These binding characteristics are shared with the homologous mammalian lectin specific for galactose/N-acetylgalactosamine, suggesting that tertiary structure of the combining area of these two lectins is similar. This is understandable, since there is approximately 40% amino acid sequence identity in the carbohydrate recognition domain of these two lectins [Drickamer, K., Mannon, J. F., Binns, G., & Leung, J. O. (1984) J. Biol. Chem. 259, 770-778]. A series of glycosides, each containing two GlcNAc residues separated by different distances (from 0.8 to 4.7 nm), were synthesized. Inhibition assay with these and other cluster glycosides indicated that clustering of two or more GlcNAc residues increased the affinity toward the chicken lectin tremendously. Among the ligands containing two GlcNAc residues, the structure which allows a maximal inter-GlcNAc distance of 3.3 nm had the strongest affinity, its affinity increase over GlcNAc (monosaccharide) amounting to 100-fold. Longer distances slightly diminished the affinity, while shortening the distance caused substantial decrease in the affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylgalactosamine↗
PubMed1982

Binding site of the rabbit liver lectin specific for galactose/N-acetylgalactosamine.

Neoglycoproteins containing various monosaccharides and disaccharides were prepared by modifying bovine serum albumin (BSA) with thioglycosides using amidination or reductive alkylation [Lee, Y. C., Stowell, C. P., & Krantz, M. J. (1976) Biochemistry 15, 3956-3963; Lee, R. T., & Lee, Y. C. (1980) Biochemistry 19, 156-163]. The binding specificity of the rabbit liver galactose/N-acetylgalactosamine specific lectin was studied with these neoglycoproteins by assaying their ability to inhibit 125I-labeled asialoorosomucoid binding to the isolated lectin or to the crude plasma membrane. The following observations were made: (1) All the galactose-containing neoglycoproteins (except two) had a similar inhibitory effect. (2) BSA derivatives containing glucose, with the sole exception of [Glc--S--CH2C(= NH)--NH]n-BSA, were poorer inhibitors than the galactose-containing BSA's, and the axial 4-OH of galactose appears to participate in the binding. (3) The binding site of the lectin for the C-6 region of galactose is apparently spacious, since a galactose substituted at the 6-OH with another monosaccharide can still be bound. (4) A negatively charged group at C-6 of galactose interfered with the binding of the lectin. (5) A bulky aglycon in an alpha-D-galactopyranoside considerably decreased the inhibitory power. For explanation of these results, it is proposed that the lectin possesses at least one negatively charged group at the binding site and the presence of this group is directly responsible for inability of the sialylated (negatively charged), native glycoproteins to bind to the mammalian hepatic lectin.

Acetylgalactosamine↗
PubMed2002

Mannopeptimycins, novel antibacterial glycopeptides from Streptomyces hygroscopicus, LL-AC98.

A series of novel antibiotics with activity against methicillin-resistant staphylococci and vancomycin-resistant enterococci has been purified, and their structures have been characterized using spectroscopic analyses and chemical conversions. These antibiotics, designated mannopeptimycins alpha-epsilon (1-5), are glycosylated cyclic hexapeptides containing two stereoisomers of an unprecedented amino acid, alpha-amino-beta-[4'-(2'-iminoimidazolidinyl)]-beta-hydroxypropionic acid (Aiha), as a distinguishing feature. The cyclic peptide core of these antibiotics is attached to a mannosyl monosaccharide moiety in 2 and to mannosyl monosaccharide and disaccharide moieties in 1, 3, 4, and 5. The presence and position of an isovaleryl group in the terminal mannose (Man-B) in 3-5 are critical for retaining antibacterial potency.

Anti-Bacterial Agents↗
PubMed2002

Soybean (Glycine max) cell wall composition and availability to feed enzymes.

Defatted untoasted soybean cotyledons and hulls were fractionated as water solutes (WSc and WSh) and water unextractable (WUc and WUh). Further fractionation of WUc through deproteinization yielded the isolation of a water unextractable solid (WUS) fraction that was mainly composed (molar percent) of galactose (28.1%), glucose (27.8%), arabinose (13.3%), and uronic acids (17.6%), which accounted for 76% of the water insoluble polysaccharides in soybean cotyledons (WUc). The cell wall (WUS) was sequentially fractionated with chelating agents (chelating agent soluble solids, ChSS) and a gradient of agents (dilute alkali, DASS; 1 M alkali, 1MASS; and 4M alkali, 4MASS), which gave a final cellulosic residue. The ChSS and DASS extracts were characterized as pectin-rich fractions, whereas 1MASS and 4MASS were hemicellulose- and cellulose-rich fractions. Incubation in vitro of the WUc fraction with pectinase, cellulase, and xylanase resulted in the release of low amounts (not more than 5% bound basis) of monosaccharides, mostly uronic acids, xylose, and arabinose. Protein extraction hardly increased this release after enzymatic incubation (<7%). However, progressive fractionation of the cell wall matrix markedly increased the release of monosaccharides from pectin- (ChSS and DASS) and hemicellulose-rich fractions (1MASS and 4MASS). Significant degradation of cellulose (up to 20%) was achieved only after complete protein, pectin, and hemicellulose extraction.

Arabinose↗
PubMed2002

Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill wastewaters.

A dark and complex metal polymeric organic mixture, named polymerin, was recovered from olive oil mill wastewaters (OMWW) and characterized by chemical analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and atomic absorption spectrometry (AAS). Polymerin proved to be composed of carbohydrates (52.40 mg 100(-1), w/w), melanin (26.14 mg 100(-1)), and proteins (10.40 mg 100(-1)), and the respective composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (11.06 mg 100(-1)), mainly K(+) and, to a lesser extent, Na(+), Ca(2+), Mg(2+), Zn(2+), Fe(3+), and Cu(2+), which were naturally bound and chelated through carboxylate anions and other characteristic nucleophilic functional groups naturally occurring in polymerin. The distribution of polymerin relative molecular size was assessed to be approximately between 500.0 and 2.0 kDa by calibrated molecular weight gel filtration chromatography, indicating also that a fraction consisted of protein, melanin, and polysaccharide, strongly aggregated to each other in a supramolecular status by a combination of covalent and hydrogen bonds and CH/Pi interactions, and another fraction of only free polysaccharide. Polymerin was transformed into a potassium salt deglycosylated derivative, named KSDpolymerin, which was also characterized by chemical analysis, DRIFTS, and AAS. KSDpolymerin consisted of carbohydrates (6.00 mg 100(-1)), melanin (52.49 mg 100(-1)), and proteins (35.40 mg 100(-1)), and the composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (6.11 mg 100(-1)), mainly K(+) and to a lesser extent Na(+), Ca(2+), Mg(2+), Zn(2+) and Fe(3+), bound as in polymerin. All the organic components were strongly linked in a supramolecular aggregate status and the relative average molecular size proved to be 6.3 kDa. Finally, we briefly discuss the possible use of such polymerins in agriculture as bioamendments and macro- and microelement biointegrators and as a biofilter for toxic metal removal, in light of their similarity with humic acids.

Chemical Phenomena↗
PubMed2004

Glycoalkaloids and metabolites inhibit the growth of human colon (HT29) and liver (HepG2) cancer cells.

As part of an effort to improve plant-derived foods such as potatoes, eggplants, and tomatoes, the antiproliferative activities against human colon (HT29) and liver (HepG2) cancer cells of a series of structurally related individual compounds were examined using a microculture tetrazolium (MTT) assay. The objective was to assess the roles of the carbohydrate side chain and aglycon part of Solanum glycosides in influencing inhibitory activities of these compounds. Evaluations were carried out with four concentrations each (0.1, 1, 10, and 100 microg/mL) of the the potato trisaccharide glycoalkaloids alpha-chaconine and alpha-solanine; the disaccharides beta(1)-chaconine, beta(2)-chaconine, and beta(2)-solanine; the monosaccharide gamma-chaconine and their common aglycon solanidine; the tetrasaccharide potato glycoalkaloid dehydrocommersonine; the potato aglycon demissidine; the tetrasaccharide tomato glycoalkaloid alpha-tomatine, the trisaccharide beta(1)-tomatine, the disaccharide gamma-tomatine, the monosaccharide delta-tomatine, and their common aglycon tomatidine; the eggplant glycoalkaloids solamargine and solasonine and their common aglycon solasodine; and the nonsteroidal alkaloid jervine. All compounds were active in the assay, with the glycoalkaloids being the most active and the hydrolysis products less so. The effectiveness against the liver cells was greater than against the colon cells. Potencies of alpha-tomatine and alpha-chaconine at a concentration of 1 microg/mL against the liver carcinoma cells were higher than those observed with the anticancer drugs doxorubicin and camptothecin. Because alpha-chaconine, alpha-solanine, and alpha-tomatine also inhibited normal human liver HeLa (Chang) cells, safety considerations should guide the use of these compounds as preventative or therapeutic treatments against carcinomas.

Alkaloids↗
PubMed2006

Membrane-assisted processing of xylooligosaccharide-containing liquors.

Liquors from rice husk autohydrolyis, containing xylooligosaccharides, other saccharides, and nonsaccharide compounds, were subjected to two selected processing schemes to increase the proportion of substituted xylooligosaccharides in refined liquors. Nanofiltration through a ceramic membrane with a molecular mass cutoff of 1000 Da allowed simultaneous concentration and purification; this latter derived from the preferential removal of monosaccharides and nonsaccharide compounds. When liquors were nanofiltered to achieve a volume reduction factor of 5 operating at a transmembrane pressure of 14 bar, 58.6% of the nonsaccharide components and 20.9-46.9% of monosaccharides were kept in retentate, in comparison with 92% of xylooligosaccharides and glucooligosaccharides. When nanofiltered liquors were subjected to double ion-exchange processing, a final product with a nonsaccharide content near 9 kg/100 kg of nonvolatile components was obtained at a yield of 10.90 kg/100 kg oven dry rice husks. Alternatively, when nanofiltered liquors were subjected to ethyl acetate extraction and further double ion-exchange processing, a purified product with a nonsaccharide content of 5.66 kg/100 kg of nonvolatile components was obtained at a yield of 9.94 kg/100 kg oven dry rice husks. The nonsaccharide components remaining in the final concentrate were mainly made up of phenolic and nitrogen-containing compounds.

Filtration↗
PubMed1999

Comparison of volatile generation in serine/threonine/glutamine-ribose/glucose/fructose model systems.

Thermal generation of volatiles in nine model reactions was studied and compared. Each of the model systems contained one amino acid and one monosaccharide. The amino acid was serine, threonine, or glutamine, and the monosaccharide was ribose, glucose, or fructose. More unsubstituted pyrazine was generated in serine-sugar systems than threonine-sugar systems. The formation of several furfuryl-substituted pyrazines and pyrroles was observed in some of the studied systems. Total pyrazines were generated more in glutamine-containing systems than in serine- and threonine-containing systems, and the reverse was true for generation of furfuryl-substituted compounds. Acetylpyrazine was generated in serine/threonine/glutamine-glucose and serine/glutamine-fructose systems.

Fructose↗
PubMed2005

Synthesis and conformational analysis of 6-C-methyl-substituted 2-acetamido-2-deoxy-beta-D-glucopyranosyl mono- and disaccharides.

Several 6-C-substituted 2-acetamido-2-deoxy-beta-D-glucopyranosides (beta-D-GlcNAc monosaccharides 1a-3a and 1,4-linked disaccharides 1b-3b) were studied by solution NMR spectroscopy. Conformational analysis of the (6S)- and (6R)-C-methyl-substituted beta-d-GlcNAc monosaccharides indicates that the stereodefined methyl groups impose predictable conformational biases on the exocyclic C-5-C-6 bond, as determined by (1)H-(1)H and (13)C-(1)H coupling constants. Variable-temperature NMR experiments in methanol-d(4) were performed to determine DeltaDeltaH and DeltaDeltaS values derived from the two lowest energy conformers. These indicate that while the influence of 6-C-methyl substitution on conformational enthalpy is in accord with the classic principles of steric interactions, conformational preference in solution can also be strongly affected by other factors such as solvent-solute interactions and solvent reorganization.

Algorithms↗
PubMed2004

Molecular recognition of carbohydrates with acyclic pyridine-based receptors.

The recognition capabilities of acyclic pyridine-based receptors toward monosaccharides were evaluated. Aminopyridine receptors based on the 2,4,6-trimethyl- or 2,4,6-triethylbenzene frame show high beta vs alpha binding selectivity in the recognition of glucopyranosides. Amidopyridine receptors, which are sterically less hindered at nitrogen, display high efficiency and an inverse selectivity. The 2-aminopyridine group has been established as a highly effective recognition group in the binding of monosaccharides. The factors influencing the binding properties of receptors 1-15, which differ in the nature and number of binding and spacer subunits used as the buildings blocks, are discussed.

Binding Sites↗
PubMed2006

Traceless Staudinger ligation of glycosyl azides with triaryl phosphines: stereoselective synthesis of glycosyl amides.

Alpha-glycosyl amides can be synthesized from the corresponding O-benzyl-alpha-glycosyl azides using a traceless Staudinger ligation with diphenylphosphanyl-phenyl esters 4. All the phosphines employed and their phenol precursors are stable to air at 4 degrees C for months. Fast intramolecular trapping of the reduction intermediates results in the direct formation of the amide link, which, in turn, prevents epimerisation and allows retention of configuration at the anomeric carbon. Yields and alpha-selectivity are high when the reaction is performed in polar aprotic solvents. Removal of the benzyl ether protecting groups is achieved by catalytic hydrogenation. Alpha-glycosyl amides represent a class of virtually unexplored nonhydrolyzable monosaccharide derivatives that may find a useful application as sugar mimics. Conformational studies by NMR spectroscopy confirm that deprotected alpha-glycosyl amides in the gluco, galacto, and fuco series retain the normal pyranose conformation of the monosaccharide. The reaction of phosphines 4 with tetra-O-acetyl-glycosyl azides is nonstereoconservative, and beta-glycosyl amides are obtained in good yields and with complete stereoselectivity starting from both alpha and beta azides.

Amides↗
PubMed2006

Torsional anharmonicity in the conformational analysis of beta-D-galactose.

Schemes to include a treatment of torsional anharmonicity in the conformational analysis of biological molecules are introduced. The approaches combine ab initio electronic energies and harmonic frequencies with anharmonic torsional partition functions calculated using the torsional path integral Monte Carlo method on affordable potential energy surfaces. The schemes are applied to the conformational study of the monosaccharide beta-d-galactose in the gas phase. The global minimum structure is almost exclusively populated at 100 K, but a large number of conformers are present at ambient and higher temperatures. Both quantum mechanical and anharmonic effects in the torsional modes have little effect on the populations at all temperatures considered, and it is, therefore, expected that standard harmonic treatments are satisfactory for the conformational study of monosaccharides.

Galactose↗
PubMed1996

Optimizing the lyophilization cycle and the consequences of collapse on the pharmaceutical acceptability of Erwinia L-asparaginase.

The antileukemia enzyme, Erwinia L-asparaginase, occurs as a tetramer which can be dissociated by the stresses of lyophilization into four subunits (subunit M(r) 34 000 Da). Dissociation can be reduced by adding protectants to the formulation to stabilize the biopolymer, while the product should dry to form a pharmaceutically elegant, shelf-stable cake which is readily soluble. Using analytical ultracentrifugation, HPLC, and circular dichroism we have related structural dissociation of the enzyme during lyophilization to biological activity. Additives such as mannitol prevent ablation loss of vial contents and dry to form cosmetically elegant cakes but provide little biological protection, since during freezing they crystallize and are removed from the preparation. Excipients persisting throughout the cycle in the amorphous state provide improved biological protection, although high molecular weight compounds such as Dextran (M(r) 70000 Da) are most effective only during product freezing or storage. Low molecular weight sugars are protective throughout the cycle although formulations containing monosaccharides often exhibit low collapse temperatures (Tc) measured using a freeze-drying microscope or glass transition temperatures (Tg') measured by thermal analysis, but these formulations distort as drying progresses to form a collapsed, cosmetically unacceptable cake, with reduced activity, poor stability, a high moisture content, and reduced solubility. Collapse can be avoided by formulating with disaccharides, which display higher Tc temperatures than monosaccharides, or drying below Tc. Dried samples which persist in the amorphous state can also collapse when stored above their solid-state collapse temperatures when they decay at a faster rate than predicted by Arrhenius kinetics. The solid-state collapse temperature can be significantly decreased by the diffusion of moisture from the stopper into the dry product resulting in an increase in sample water content. Lyophilization cycle times can be reduced by analyzing collapse characteristics so that the relationship between product temperature and chamber pressure can be controlled so that drying rates can be optimized while ensuring that the product does not melt or collapse during sublimation.

Antineoplastic Agents↗
PubMed1997

Contrasting nutrient effects on the plasma levels of an amino acid-like antiepileptic agent from jejunal administration in dogs.

The absorption of gabapentin was investigated by monitoring drug plasma levels as a function of time following midjejunal administration in mongrel dogs. From previous work, dose-dependent absorption had been postulated to be a consequence of carrier-mediated transport and a paracellular pathway had been postulated to contribute to the passive absorption component in mammalian small intestine. The potential for amino acid inhibition of the carrier-mediated absorption component was investigated by drug coinfusion with leucine and phenylalanine. The potential for monosaccharide-enhanced increases in drug absorption was studied by drug coinfusion with D-glucose and 3-O-methylglucose. While lower drug plasma levels were observed with amino acid coinfusion versus controls in each of the dogs studied, mean area under the plasma level time curves (AUC) were not statistically significantly different (p < or = 0.07). Monosaccharide coinfusion significantly increased gabapentin AUC over control studies (p < or = 0.014) and over coinfusion with L-system amino acids (p < or = 0.0025). Implications for the mechanisms of intestinal absorption of this amino acid-like antiepileptic drug in this canine model are discussed.

Acetates↗
PubMed2005

The interaction of boronic acid-substituted viologens with pyranine: the effects of quencher charge on fluorescence quenching and glucose response.

The fluorescence sensing of several monosaccharides using boronic acid-substituted viologen quenchers in combination with the fluorescent dye pyranine (HPTS) is reported. In this two-component sensing system, fluorescence quenching by the viologen is modulated by monosaccharides to provide a fluorescence signal. A series of viologen quenchers with different charges were prepared and tested for their ability both to quench the fluorescence of HPTS and to sense changes in glucose concentration in aqueous solution at pH 7.4. Both quenching efficiency and sugar sensing were found to be strongly dependent upon viologen charge. The molar ratio between HPTS and each of the viologen quenchers was varied in order to obtain an optimal ratio that provided a fairly linear fluorescence signal across a physiological glucose concentration range. Both the quenching and sugar sensing results are explained by electrostatic interaction between dye and quencher.

Arylsulfonates↗