Laser-raman spectra of d-glucose and sucrose in aqueous solution

Laser-Raman spectra of d-glucose in water at various concentrations were recorded below 1700 cm^?1. Assignments of the frequencies of d-glucose were proposed, based on earlier work on the vibrational spectra of this sugar, and determination by other techniques of the anomeric composition of aqueous solutions of d-glucose. The proportions of the anomers found from the ratio of the Raman intensities for the same models of vibrations were similar to those found by other techniques. Assignments of the frequencies for sucrose were proposed, in the light of previous results on d-glucose and d-fructose, and the effect, on their Raman spectra, of the condensation of these two monosaccharides was pointed out.     

X-ray diffraction study of the molecular association in aqueous solutions of d-fructose, d-glucose,and sucrose

X-ray diffractograms of aqueous solutions of d-fructose, d-glucose, and sucrose, and of two amorphous “solid” forms of these carbohydrates are recorded in the angular range of O 2-16°. The formation, in these diffractograms, of one or two intensity maxima as the concentration is varied is interpreted in terms of modification of the molecular association. A model is proposed that takes account of the state of organization of the solutions of the three sugars as a function of the concentration. Sucrose shows an “anomaly”, as it is the only sugar to establish intramolecular bonds. The number of these intramolecular bonds also depends on the concentration.     

Laser-raman spectra of d-fructose in aqueous solution

Laser-Raman spectra of d-fructose in water at different concentrations were recorded, and assignments of the frequencies were proposed, based on earlier work on the Raman spectra of other sugars, and determination by other techniques of the composition of aqueous solutions of d-fructose as regards different isomers. It was found that the frequencies of vibration of the furanoid are higher than those of the pyranoid ring. The proportions of the furanoses and pyranoses, found from the ratio of the Raman intensities for the same modes of vibration, were similar to those found by other techniques. Shifts of intensities and frequencies were observed in the region of OH and CH bands, and were assigned to probable association between molecules of d-fructose and water.     

Effects of various conditions on the alkaline degradation of d-fructose and d-glucose

Dilute solutions of d-fructose and d-glucose undergo alkaline degradation, and, at temperatures in the range of 30–70°, almost two moles of alkali are consumed per mole of the carbohydrate. The degradation is partly guided by the dielectric constant of the medium; such additives as acetone and urea have specific effects where the reactions are not essentially guided by the medium dielectric. Acetone and urea presumably form complexes with the carbohydrates; this is revealed for the former by the formation of a dark red solution having a spectral band at 320 nm, like that observed earlier in the presence of ethylenediamine.     

The effect of areneboronic acids on the alkaline conversion of d-glucose into d-fructose

Benzeneboronic acid, 4-methoxybenzeneboronic acid, 3-nitrobenzeneboronic acid, and sulphonated benzeneboronic acid have been used to displace the pseudo-equilibria established in aqueous alkali between d-glucose, d-fructose, and d-mannose to give greatly increased yields of d-fructose. The effect of reaction temperature, pH, overall concentration, and molar ratio of acid:sugar on the yield of d-fructose has been investigated by using an automated assay for d-fructose.     

Rapid and sensitive,colorimetric determination of the anomers of d-glucose with d-glucose oxidase,peroxidase, and mutarotase

A modification, utilising mutarotase, of an enzymic, colorimetric system for determining d-glucose with d-glucose oxidase, peroxidase, and ABTS was satisfactory for the assay of the anomers of d-glucose in aqueous solution. The time required for a single assay is ≈ 10 min, and the lower limit is 0.4 μg of d-glucose. The method is applicable to the anomer analysis of d-glucose released by enzymic hydrolysis of d-glucosides.     

Nature of the uptake of d-galactose, d-glucose and α-methyl-d-glucoside by Saccharomyces cerevisiae

Both glucose-grown baker's yeast after induction and galactose-grown yeast appear to take up d-galactose by a system not requiring phosphorylation and only up to a diffusion equilibrium, as shown by pulse labelling, sampling at very short intervals and chromatographic analysis of extracts. Part of the sugar taken up is transformed into trehalose which is present in substantially greater amounts in cells than the transported sugar itself. The effect of 2,4-dinitrophenol and of iodoacetamide, as well as the nature of the efflux of sugars from preloaded cells, support the results. d-Glucose and α-methylglucoside are also taken up without phosphorylation.     

Isomerization of d-fructose by base: Liquid-chromatographic evaluation and the isolation of d-psicose

Several bases have been evaluated as catalysts for the production of d-psicose (d-ribo-2-hexulose) from d-fructose. The hexose levels in the isomerized mixtures were quantified by l.c. on a μBondapak/Carbohydrate column. The most effective and convenient base was found to be pyridine, and mixtures produced by boiling concentrated solutions (1 g/mL) of d-fructose in pyridine under reflux contained 12.4% of psicose, lesser proportions of glucose and mannose, and 25.8% of the starting material. Following removal of solvent, fermentation with bakers' yeast removed most hexoses other than d-psicose, which was isolated by chromatography on cellulose. The entire procedure required three days, and d-psicose was obtained in gram quantities in 6.8% of the theoretical yield.     

Specific d-glucose transport in sarcolemma vesicles

The sarcolemmal fraction prepared from rat skeletal muscle consists of osmotically active vesicles that accumulate d-glucose in preference to l-glucose, apparently by facilitated diffusion into intravesicular space. Stereospecific d-glucose uptake by these vesicles is a saturable process, inhibited by phloridzin, by cytochalasin B, and by certain sugars, and enhanced by counterflow. An additional leak pathway permits entry of both d- and l-glucose into the vesicles.Stereospecific d-glucose transport by sarcolemmal vesicles is enhanced to a small extent by insulin, provided the hormone is administered prior to cell disruption. In membranes prepared from insulin-pretreated muscle, Ca²⁺ produces a small further enhancement. Local anesthetics preferentially inhibit stereospecific d-glucose transport. Apparent uptake of both d- and l-glucose is greater when vesicles are suspended in salt solutions rather than sucrose, an effect attributed to increased functional vesicular volume.     

Synthesis and growth regulator activity of fatty acyl derivatives of d-glucose and d-galactose

In an attempt to gain information about one or more components of the brassin complex, fatty acid esters of d-glucose and d-galactose were prepared and tested for growth regulator activity in a bean hypocotyl bioassay. 4-O-Acyl-d-glucoses and, perhaps, 1-O-acyl- d-galactoses had a similar qualitative activity to that of the brassin complex. 3-O-Acyl- d-galactoses inhibited elongation of bean hypocotyls and stimulated rooting. 3- And 6-O- acyl-d-glucoses both stimulated and inhibited elongation, depending on the source of fatty acids; in both cases, stimulation was observed when safflower oil was used as the source of fatty acids and inhibition was observed when peanut oil was used as the source of fatty acids. Fatty alkyl β-d-galactopyranosides were inactive.     

Photolysis of d-fructose in aqueous solution

In the 254-nm photolysis of aqueous solutions of d-fructose, only the openchain form, which is present to an extent of 0.8% in equilibrium with the cyclic forms, absorbs the light. A study of the products and their quantum yields reveals that the main, primary process is C--- bond cleavage α to the carbonyl group. In the absence of oxygen, the subsequent reactions of the resulting radicals are (a) loss of CO from the hydroxyalkylacyl radicals (estimated rate constant a 3 × 10⁶ s⁻¹); (b) consecutive elimination of two molecules of water from the tetritol radicals; and (c) disproportionation and combination reactions. A peculiar products is trans-4-hydroxy-2-butenal, whose precursor is formed from the tetritol radical through elimination of two molecules of water. This compound is a good radical-scavenger and during photolysis quickly attains a low steady-state concentration. One of the products derived from it is a 2,3-dideoxy-2,3-di-C-hydroxymethyltetrose. In the presence of oxygen, the CO elimination process is partly, and the water elimination reactions are fully, suppressed by the fast addition of oxygen to the acylalkyl and hydroxyalkyl radicals. The peroxyl radicals react through unimolecular elimination of HO₂ from α-hydroxyalkylperoxyl radicals and bimolecular dismutation with loss of O₂, accompanied by loss of CO₂ when hydroxyalkylacylperoxyl radicals are involved.     

Electrokinetic studies of the testosterone-aqueous d-glucose interface

Electro-osmosis and streaming-potential measurements were made across a testosterone-plug membrane, using water and aqueous solutions of d-glucose as permeants. The electrophoretic velocity of testosterone particles dispersed in these solutions was also measured, experiments being confined to the range where linear flux-force relationships hold. Phenomenological coefficients were evaluated by using these linear relations, and the results analyzed inthe light of the thermodynamics of irreversible processes. Saxen's relationship holds between electro-osmosis and streaming potential. Concentration dependence of the various phenomenological coefficients was also examined. Cross-phenomenological coefficients were found to decrease with increase in the concentration of d-glucose solutions. The results are explained on the basis of strong hydrogen-bonding between d-glucose and the surrounding water molecules. Such membrane parameters as pore size, average number of pores, and the membrane constant were evaluated. Electro-osmotic and electrophoretic data were used to estimate the zeta potential, in order to characterize the membrane-permeant interface. The dependence of the zeta potential on the concentration was also examined.     

Temperature dependence of d-glucose transport in reconstituted liposomes

Sodium-dependent d-glucose uptake into proteoliposomes reconstituted from dimyristoylphosphatidylcholine (DMPC) and hog kidney brush border membrane extract is strongly affected by temperature and the physical state of the membranes. This dependence is defined by a nonlinear Arrhenius plot with a break point at 23°C, a temperature not significantly different from the phase transition temperature of the pure lipid (24°C). The transport process is characterized by different activation energies: 35.1 kcal/mol below and 5.5 kcal/mol above the transition temperature. The shift in the break point for the d-glucose transport activity from 15°C, in the brush border membranes, to 23°C in the reconstituted system leads us to conclude that the lipids surrounding the sodium/d-glucose cotransport system can exchange readily with the bulk lipid used for reconstitution. The results thus provide no evidence for the presence of an annulus of specific lipids surrounding the transport system.     

The hydrothermolysis of cellobiose and its reaction-product d-glucose

The hydrothermolysis of cellobiose in the range 180–249° has been studied. Kinetic analysis of the reaction showed that 60% of the cellobiose is converted into d-glucose, and 40% into other products. The rate (k₁) of cellobiose disintegration is approximately eight times that (k₂) of d-glucose. Thus, hydrothermolysis differs from acidic hydrolysis. Hydrothermolysis is not dependent on pH, at least in the range 3–7.     

Metabolism of 14C-labelled D-glucose, D-fructose and allitol by Itea plants

The metabolism of D-[1-¹⁴C]glucose, D-[6-¹⁴C]glucose, D-[1-¹⁴C]fructose and D-[6-¹⁴C]fructose by leafy spurs of Itea plants results in rapid incorporation of label into allitol and D-allulose. The patterns of labelling found in the allitol and D-allulose are discussed, a direct interconversion from D-glucose and D-fructose being indicated. Allitol has been found to be an active metabolite in Itea plants.     

Enzymic determination of d-galactose, d-arabinose,and their homologs

The enzymes d-galactose dehydrogenase and d-arabinose dehydrogenase were demonstrated to be applicable to the quantitative determination of d-galactose (and homologs) and d-arabinose (and homologs), respectively. The enzymic reactions were quite specific. When coupled with β-galactosidase, d-galactose dehydrogenase could be used in the quantitative determination of β-galactosides.     

A microplate assay for d-xylose/ d-glucose isomerase

A modification of the resorcinol method of Kulka¹ for the determination of ketoses is described. Though being a stopped enzyme test, it is much more sensitive than the carbazol method and by applying microtiter plates and measuring with an ELISA reader, a large number of tests can be performed within a short time, thereby facilitating initial velocity studies.

The test is linear up to a concentration of 2.5 m -xylulose even in the presence of 10 m -xylose and 2 m -fructose in the presence of 10 m -glucose. The sensitivity is 25 μ for xylulose and 38 μ for fructose. The test method is insensitive to perturbations of substances frequently used in isolation procedures such as ammonium sulfate, Triton X-100, PEG 6000, sodium dodecyl sulfate, and ethanol in moderate concentrations.     

Phenylalanine ammonia-lyase: Mirror-image packing of d- and l-phenylalanine and d- and l-transition state analogs into the active site

The binding of substrate and product analogs to phenylalanine ammonia-lyase (EC 4.3.1.5) from maize has been studied by a protection method. The ligand dissociation constants, K_L, were estimated from the variation with [L] of the pseudo-first-order rate constants for enzyme inactivation by nitromethane. The phenylalanine analogs d- and l-2-aminooxy-3-phenylpropionic acid showed K_L, values over 20,000-fold lower than the K_m for l-phenylalanine. From these and other K_L values it is deduced that when the enzyme binds l-phenylalanine the structural free energy stored in the protein is higher than when it binds the superinhibitors. Models for binding d- and l-phenylalanine and the superinhibitors are described. The enantiomeric pairs are considered to have similar K_L values because they pack into the active site in a mirror-image relationship. If the elimination reaction approximates to the least-motion course deduced on stereoelectronic grounds, the mirror-image packing of the superinhibitors into the active site mimics the conformation inferred for a transition state in the elimination. It appears, therefore, that structural changes take place in the enzyme as the transition state conformation is approached causing stored free energy to be released. This lowers the activation free energy for the elimination reaction and accounts for the strong binding by the above analogs.