Disaccharides In Aqueous Solution Research Articles

Binuclear copper(II) complexes discriminating epimeric glycosides and α- and β-glycosidic bonds in aqueous solution

Two chiral binuclear copper(II) complexes were synthesized and characterized for the first time as efficient chemoselective catalysts for the hydrolysis of aryl glycosides and disaccharides in aqueous solution at near neutral pH. Under these conditions, discrimination of epimeric aryl α-glycopyranosides was observed by both 29-fold different reaction rates and 3-fold different proficiency of the catalyst. Additionally, large differentiation of the nature of α- and β-glycosidic bond in aryl glycosides as model compounds is apparent, but also noted in selected disaccharides. The influence of the chirality of the complexes and the role of the configuration of the carbohydrate upon interaction with the catalyst is discussed in detail. Lastly, a putative mechanism for the metal complex-catalyzed hydrolysis is derived from the experimental evidence pointing at deprotonation of the hydroxyl group at C-2 as a pre-requisite for glycoside hydrolysis.

Novel Boronlectins Based on Bispyridium Salt with a Flexible Linker: Discriminative Sensing of Lactose and Other Monosaccharides and Disaccharides in Aqueous Solution.

N,N-Di-2-picolylamine (DPA)-derived diboronic acid receptors (NHBAs) with a flexible linker were designed and synthesized in this study, and two-component sensing ensembles based on cationic NHBAs and an anionic fluorescent indicator 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) were successfully developed for both monosaccharides and disaccharides sensing. The dibranched ortho-substituted receptor NHoBA exhibited unexpected selectivity towards lactose among five disaccharides used. The discrimination of five disaccharides and six monosaccharides was finally achieved by the integrated sensor array through linear discriminant analysis (LDA).

Volumetric Properties of Disaccharides in Aqueous Solutions of Benzyldimethylammonium Acetate as a Function of Temperature

Densities, ρ, and speeds of sound, u, of two disaccharides (D-(+)-maltose and D-(+)-cellobiose) in water and in the presence of protic ionic liquid (PIL) (i.e., benzyldimethylammonium acetate, BDMAAc) were measured at different temperatures (288.15–318.15) K at atmospheric pressure. These data were used to calculate the apparent molar volume, apparent molar isentropic compressibility, infinite dilution partial molar volume, infinite dilution partial molar isentropic compressibility, and corresponding transfer parameters (ΔtV°2 and ΔtK°s,2) for disaccharides from water to aqueous PIL solutions. The effect of BDMAAc on the basic taste quality of disaccharides was evaluated from apparent specific volume and apparent specific isentropic compressibility, as these parameters are grouped in various taste qualities.

Peptide‐Based Carbohydrate Receptors

A broad spectrum of physiological processes is mediated by highly specific noncovalent interactions of carbohydrates and proteins. In a recent communication we identified several cyclic hexapeptides in a dynamic combinatorial library that interact selectively with carbohydrates with high binding constants in water. Herein, we report a detailed investigation of the noncovalent interaction of two cyclic hexapeptides (Cys-His-Cys (which we call HisHis) and Cys-Tyr-Cys (which we call TyrTyr)) with a selection of monosaccharides and disaccharides in aqueous solution. The parallel and antiparallel isomers of HisHis or TyrTyr were synthesized separately, and their interaction with monosaccharides and disaccharides in aqueous solution was studied by isothermal titration calorimetry, NMR spectroscopic titrations, and circular dichroism spectroscopy. From these measurements, we identified particularly stable complexes (Ka> 1000 M(-1)) of the parallel isomer of HisHis with N-acetylneuraminic acid and with methyl-a-d-galactopyranoside as well as of both isomers of TyrTyr with trehalose. To gain further insight into the structure of the peptide–carbohydrate complexes, structure prediction was performed using quantum chemical methods. The calculations confirm the selectivity observed in the experiments and indicate the formation of multiple intermolecular hydrogen bonds in the most stable complexes.

Effect of Sodium Sulphate on the Volumetric, Rheological and Refractometric Properties of some Disaccharides in Aqueous Solutions at Different Temperatures

Density,ρ, viscosity,η, and refractive index,n, of some disaccharides [D(+)-cellobiose, D(+)-lactose monohydrate, D(+)-maltose monohydrate and sucrose] in water and in 0.49850 and 0.99705mol kg-1aqueous solutions of sodium sulphate [Na2SO4] have been measured at four temperatures [288.15, 298.15, 308.15 and 318.15K]. From these data, the apparent molar volumes,VΦ, and viscosity-B-coefficients using Jones–Dole equation have been determined at different temperatures. The partial molar volumes of transfer,ΔtV20at infinite dilution and B-coefficients of transfer,ΔtB, have been estimated for transfer of disaccharides from water to aqueous sodium sulphate solutions. Partial molar expansion coefficients, (∂V20/∂T)Pand dB/dTcoefficients have also been calculated. Gibbs free energy of activation of viscous flow has been calculated by using Feakin´s transition-state theory for the studied systems. D(+)-Cellobiose has shown characteristically different hydration behaviour among the studied disaccharides. The signs and magnitude ofΔtV20, andΔtB parameters have been discussed in terms of various interactions occurring in these solutions.

Measurement Analysis of Glass Transition Temperature for Sucrose and Trehalose Aqueous Solutions

Glass transition temperatures (Tg) for sucrose, trehalose, and water have been determined by numerous studies in the past. Literature values appear to be fairly scattered and compromise the applicability of the Gordon–Taylor equation for aqueous solutions. This work deals with the effect of the sample history and heating process on the Tg values. Consistent estimates for the glass transition temperature of both disaccharides in aqueous solution can be made from these observations.

Water–disaccharides interactions in saturated solution and the crystallisation conditions

This paper reports solubility data and measurements of viscosity of the saturated aqueous solutions of sucrose, maltitol, and trehalose. Likewise, the metastable zone width and velocity of nucleation of the three disaccharides are compared. The narrowest metastable zone is observed for maltitol and the largest for trehalose. Such behaviour is due to a higher affinity of trehalose for water. Moreover, the crystallisation of anhydrous disaccharides in aqueous solution necessitates that hydration water be removed and evacuated from crystal integration surface to the bulk of solution to allow the growth of crystals. This step of disassociation and diffusion of hydration water proves to be the controlling step of the crystallisation process. Structural features at the origin of the differences between the three sugars are studied by FTIR spectroscopy. Modifications of frequencies and intensities of the vibrations around the glycosidic bond are interpreted in terms of conformational flexibility. Arguments like H-bond strength or conformational flexibility of the two monomers around the glycosidic oxygen were evoked as possible explanations of the behaviour of disaccharides. Likewise stability of hydration of the disaccharides is derived from the interpretation of FTIR spectra. These structural features help in interpreting the differences in crystallisation conditions and to hypothesize about the cryoprotective ability of the studied molecules.

Effect of the Type of Glycosidic Linkage on the Selective Interactions of Maltose and Cellobiose with Some Crown Ethers in Dilute Aqueous Solutions

Titration calorimetric and densimetric measurements have been applied to study the selective interactions of two disaccharides composed of two glucose units, maltose and cellobiose, with 15-crown-5 and 18-crown-6 in dilute aqueous solutions. Maltose and cellobiose form thermodynamically stable complexes with different stoichiometries with 18-crown-6 but not with 15-crown-5. The obtained results are explained by the different states of the disaccharides in aqueous solution due to effect of the type of linkage between glucose units

Influences of Monosaccharides and its Glycosidic Linkage on Infrared Spectral Characteristics of Disaccharides in Aqueous Solutions

The infrared spectral characteristics of ten different types of disaccharides (trehalose, kojibiose, nigerose, maltose, isomaltose, trehalulose, sucrose, turanose, maltulose, and palatinose) and five different types of monosaccharides (glucose, mannose, galactose, talose, and fructose) in aqueous solutions (H2O and D2O) were determined. The infrared spectra were collected using the Fourier transform infrared attenuated total reflectance (FT-IR/ATR) method and comparisons between the degrees of absorption band-shift of the saccharide spectra in the H2O solution with those in the D2O solution with respect to the saccharide concentrations were done. The study revealed that the wavenumber shifts in the bands of mono- and disaccharides in the H2O and D2O solutions could be used as an indicator of the level of interaction between the saccharides and water. The study also focused on the glycosidic linkage position and the constituent monosaccharides and found that they have a significant influence on the infrared spectroscopic characterization of disaccharides in an aqueous solution.

Molecular Dynamics and Conformational Kinetics of Mono‐ and Disaccharides in Aqueous Solution

Acoustical attenuation spectra between 10 kHz and 2 GHz, complex dielectric spectra between 300 kHz and 40 GHz, and time-resolved non-equilibrium measurements are reported for aqueous solutions of various mono- and disaccharides with and without 2:1 valent salts. The spectra reveal a variety of relaxation regimes with relaxation times between 1 micros and 10 ps. In addition, the time-resolved observations enable the study of the mutarotation with relaxation times on the order of 10(3) s. Variation of the concentration and temperature as well as a careful choice of the saccharides allow a discussion of the relaxation processes in terms of a chair-chair ring inversion, two modes of pseudorotation, an exocyclic hydroxymethyl group rotation, a carbohydrate-carbohydrate association, and, in the disaccharide solutions, a rotation of the rings relative to another. Salt-containing solutions show also relaxation phenomena reflecting different steps cation-carbohydrate association and variations in the carbohydrate conformational isomerizations and associations due to interactions with cations.

Studies of Disaccharide Solvation—Molecular Dynamics versus HPLC Retention

Molecular dynamics simulations have been used to assess the conformational behaviour of seven disaccharides in aqueous solution. Solvation decreased the overall conformational fluctuations of the sugars, compared to in vacuo simulations using a high dielectric constant. The most significant finding was a linear correlation between the experimental chromatographic retention parameter K´ and a molecular modelling parameter based on the next-nearest oxygen–oxygen distances in the disaccharides. The results support previous proposals for a stereospecific hydration model for carbohydrates and demonstrate the utility of a combined experimental/molecular modelling approach to its study.

Conformational kinetics of disaccharides in aqueous solutions.

Between 100 kHz and 2 GHz ultrasonic attenuation spectra of disaccharides in water have been measured at 25 degrees C. Some additional measurements have been performed at different temperatures between 10 and 35 degrees C and as a function of saccharide concentration c (0.5 mol/l</=c</=1.8 mol/l). The analytical description of the spectra in terms of relaxation spectral functions revealed four relaxation regimes. Three relaxation regions correspond to such revealed by monosaccharides in solution. These relaxations reflect a pseudorotation, an exocyclic hydroxymethyl group rotation, and probably a saccharide-saccharide association. The relaxation term with relaxation time between 3.6 and 19 ns (25 degrees C) is characteristic for the disaccharide solutions. It has been assigned to a rotation of the disaccharide rings relative to one another.

Ab initio conformational maps in the gas phase and aqueous solution for a prototype of the glycosidic linkage

Ab initio conformational maps for methoxyethoxymethane (MEM) in both the gas phase and aqueous solution have been constructed using two different approaches. The results obtained allow us to conclude that a rigid conformational map is able to predict the regions of the minima, in the potential energy surface of MEM, in full agreement with those found in the relaxed conformational map, in both phases studied. This is a good indication that ab initio rigid conformational maps may be reliably used to sort the stablest conformers of disaccharides in aqueous solution. Besides that, in the MEM case, the solvation effects do not give rise to any new local minimum in its potential energy surface, but just change the relative energies of the stablest conformers found in the gas phase. This may be an indication that even in aqueous solution the anomeric effect is still the determinant effect defining the conformation of the molecule.

NMR and modelling studies of disaccharide conformation

Long-range heteronuclear coupling constants were measured across the glycosidic linkages for a series of eight α- or β-linked disaccharides in aqueous solution. Multiple 13C site-selective excitation experiments using 1H decoupling in conjunction with pulsed field gradient-enhanced spectroscopy were used to determine 3 J C,H values. These were subsequently compared with the respective couplings calculated, using a Karplus relationship, from molecular dynamics simulations with the explicit inclusion of water.

Enzyme-Based Sensor Arrays for Rapid Characterization of Complex Disaccharide Solutions

An enzyme-based sensor array has been developed to detect multiple disaccharides in aqueous solutions. Porous agarose beads, derivatized with enzymes for assaying disaccharides, are localized within wells etched into a silicon chip in a regular 5 × 7 array. Each well is individually addressable and acts as a microanalysis chamber where sample solution passes through the agarose matrix and is exposed to the enzymes. Detection is achieved by observing the increase in absorbance of a quinoneimine dye produced during the reaction. This technique is used to quantify the disaccharides lactose, sucrose, and maltose and the monosaccharide glucose. Preexisting glucose in the sample complicates multicomponent sensing but can be accounted for by including a glucose sensor in the array. This detection strategy is applied to the simultaneous analysis of these sugars in several beverages.

1H NMR chemical shifts of hydroxy protons in conformational analysis of disaccharides in aqueous solution

In a continuing study on the use of hydroxy protons in conformational analysis of saccharides in aqueous solution by NMR spectroscopy, a number of disaccharides with 1,3-, 1,4- and 1,6-linkages have been investigated. The 1H-NMR chemical shifts, vicinal coupling constants (3JCH,OH), temperature coefficients and rates of exchange with the solvent have been measured for the hydroxy protons. Most of the hydroxy proton signals in the disaccharides have chemical shifts similar (|Δδ| ≤ 0.3 ppm) to those in the corresponding methyl monosaccharides. Three hydroxy protons, however, O(2)H in β-L-Fucp-(1→3)-α-D-Glcp-OMe, O(3)H in β-L-Fucp-(1→4)-α-D-Galp-OMe and O(6)H in β-L-Fucp-(1→4)-α-D-Glcp-OMe show a large upfield shift (Δδ ≤ −0.3 ppm) attributed to the proximity of the hydroxy proton to the ring oxygen of the neighbouring sugar. In β-L-Fucp-(1→4)-α-D-Galp-OMe, the chemical shift, 3JCH,OH and temperature coefficient of the O(3)H signal indicate that a weak hydrogen bond interaction exists between O(3)H and O(5′). In β-L-Fucp-(1→4)-α-D-Glcp-OMe, the chemical shift and the NOEs involving the O(6)H signal suggest a preference for the trans-gauche conformation around the C5–C6 bond.

The structure and (local) stability constants of borate esters of mono- and di-saccharides as studied by 11B and 13C NMR spectroscopy

The formation of borate esters of various mono- and di-saccharides in aqueous solution was studied by 11B and 13C NMR spectroscopy. Association constants K(B −L) at a carbohydrate-borate molar ratio of 1:1, pH 7, and 25°C were determined and compared with literature values obtained from potentiometry. The association constants K(B −L) were converted into local association constants K loc(B −L) by using the distribution of the various anomeric forms in D 2O. In this way, values of K loc(B −L) were obtained, which appear to be characteristic of the configuration concerned. They explain the favourable effect of borate in the alkaline isomerisation of lactose into lactulose. At a low molar ratio (1:3) of carbohydrate-borate, predominantly diborate esters (B −) 2L were formed.

Concerning the tumbling motion of disaccharides in aqueous solution

Concerning the tumbling motion of disaccharides in aqueous solution