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beta-Sitosterol, beta-sitosterol-beta-D-glucopyranoside and a butyrolactone lignan disaccharide, ramontoside, were isolated from the heartwood of Flacourtia ramontchi. The structure of ramontoside was determined as diphyllin-4-O-[beta-D-glucopyranosyl(1---4)]-beta- 2,3-di-O-methyl-D-xylopyranoside by hydrolysis and spectral data.
The activity of amino acid transport System A in avian fibroblasts was increased following incubation of the cells in a medium in which most of the NaCl normally present had been isoosmotically replaced by sucrose. This increase was detectable after 2 h of incubation, reached a maximum at about 4 h, and remained constant thereafter. Transfer of treated cells back to a normal medium resulted in decay of the induced transport activity, with a half-life of less than 2 h. Kinetic analysis revealed that the increase in transport activity arose from an increase in Vmax, with little change in Km. This induction of System A activity did not occur if an inhibitor of either RNA or protein synthesis was present in the modified medium. The use of various different solutes as replacements for NaCl in the incubation medium showed that, although each replacement caused a decrease in both cellular Na+ content and protein synthesis, only disaccharides produced the increase in amino acid transport activity. In addition, estimates of cell volume indicated that, even under iso-osmotic conditions, incubation in the sucrose-containing medium caused initial cell shrinkage, followed by swelling. It is concluded that this induction of System A activity is associated with a volume regulatory process and that this process probably accounts for the parallel responses previously observed when cells were incubated in hyperosmolar media. Induction of amino acid transport activity by this process is distinct from adaptive regulation, caused by amino acid starvation; but the two processes are not strictly additive, and so appear to converge at some step.
Genetically related diploid strains of Saccharomyces cerevisiae that accumulate varied amounts of trehalose during starvation for nitrogen have been constructed. Strains that produced greater than 5% trehalose (dry cell weight) were more tolerant of thermal, or freeze-thaw stresses than strains that produced less than 4% trehalose. Thus trehalose appears to play a role in stress tolerance of yeast. The significance of these results is that, for the first time, a series of related, unmutated strains have been used to test the effect of trehalose on thermotolerance. Previous studies employed either heat shock treatment, or mutated strains to provide trehalose variations, and as such the contribution of the disaccharide to stress tolerance could not necessarily be separated from other factors such as heat shock proteins.
Membranes for determination of maltose, lactose and sucrose with the use of an oxygen electrode are described. They were obtained by immobilization of glucose oxidase with suitable disaccharide hydrolase in gelatin or albumin. For the sucrose determination mutarotase was also used. The membranes contained one, two or three enzymes working in sequence. The enzyme composition of the membranes influenced the linear range slightly and the value of electrode response considerably. The electrode response of the maltose membranes was also affected by the immobilization material. The measurements with the use of enzymatic membranes were very sensitive to temperature and, to some degree, the pH of the sample. Stability of the membranes was differentiated. The albumin membranes for sucrose determination generated almost the same signal after 1 month of frequent use, whereas the gelatin membranes for lactose determination lost about 85% of the initial activity after 1 week of operation. The electrode response of both the gelatin and albumin maltose membranes decreased in the same time by about 50%.
Beta-rhamnosylation of methyl 2-C-hydroxymethyl-2,3-O-isopropylidene-beta-D-erythrofuranoside and methyl 2,3-O-isopropylidene-beta-D-ribofuranoside was achieved using 4-O-acetyl-2,3-O-carbonyl-alpha-L-rhamnopyranosyl bromide and Ag2O as a promoter. Deprotected disaccharides beta-L-Rhap-(1-->3')-beta-D-Apif-OMe and beta-L-Rhap-(1-->3')-beta-D-Ribf-OMe were compared to their alpha-rhamnosyl isomers which were prepared using conventional Helferich glycosylation.
A simple and reproducible method for the qualitative and quantitative analysis of free mono- and disaccharides (fructose, glucose, galactose, sucrose, lactulose and lactose) in milk-based formulae by high-performance liquid chromatography (HPLC) with refractive index (RI) detection was developed and validated. The method showed good linearity with determination coefficients exceeding 0.99. The limits of detection (DL) in these sugars were 0.17, 0.13, 0.06, 0.16, 0.05 and 0.25 mg/ml, respectively; and the limits of quantification (QL), 0.27, 0.24, 0.20, 0.26, 0.22 and 0.38 mg/ml. The relative standard deviations (R.S.D.s) for repeatability in fructose, sucrose, lactulose and lactose were 0.78, 0.99, 2.91 and 0.46 and the R.S.D.s for reproducibility were 4.8, 6.15, 7.04 and 2.49, respectively. Recoveries in all sugars were between 93 and 113%.
The disaccharide trehalose is well known for its bioprotective properties. Produced in large amounts during stress periods in the life of organisms able to survive potentially damaging conditions, trehalose plays its protective role by stabilizing biostructures such as proteins and lipid membranes. In this study, molecular dynamics simulations are used to investigate the interaction of trehalose with a phospholipid bilayer at atomistic resolution. Simulations of the bilayer in the absence and in the presence of trehalose at two different concentrations (1 or 2 molal) are carried out at 325 K and 475 K. The results show that trehalose is able to minimize the disruptive effect of the elevated temperature and stabilize the bilayer structure. At both temperature, trehalose is found to interact directly with the bilayer through hydrogen bonds. However, the water molecules at the bilayer surface are not completely replaced. At high temperature, the protective effect of trehalose is correlated with a significant increase in the number of trehalose-bilayer hydrogen bonds, predominantly through an increase in the number of trehalose molecules bridging three or more lipid molecules.
A degradation protocol using de-O-acylation and subsequent alkaline de-N-acylation was applied to the lipopolysaccharide of Ochrobactrum anthropi rough strain LMG 3301. Three main oligosaccharide bisphosphates containing core-lipid A backbone structures were obtained after fractionation by anion-exchange HPLC. Using 1H and 13C NMR spectroscopy, including two-dimensional COSY, TOCSY, and NOE spectroscopy (ROESY and NOESY), the following structures were established: [formula: see text] where Kdo is 3-deoxy-D-manno-octulosonic acid, D-GlcN3N is 2,3-diamino-2,3-dideoxy-D- glucose and R is H or alpha-D-GalpA or 4-deoxy-beta-L-threo-hex-4-enopyranuronic acid, the latter sugar being derived from alpha-D-GalpA by beta-elimination of a substituent attached to 0-4. This is the first report on the isolation from a lipopolysaccharide of an oligosaccharide containing GlcN3N in the lipid A backbone [beta-D-GlcpN3N4P-(1-->6)-alpha-D-GlcpN3N1 P]. Sugar and methylation analysis confirmed the presence of the GalA-->Kdo disaccharide and non-stoichiometric substitution of GalA. It is suggested that Glc is the substituent at 0-4 in GalA and that in the non-degraded lipopolysaccharide the amino group of GlcN is not acylated.
The monosaccharide (D-fructose, D-glucose, anhydrosugars), disaccharide (glucobioses) and pseudodisaccharide (di-D-fructose dianhydrides) content of D-fructose, D-glucose and sucrose caramels has been determined by gas-liquid chromatography-mass spectrometry (GLC-MS) of their trimethylsilyl (TMS) or TMS-oxime derivatives. The chromatographic profiles revealed significant differences in the disaccharide/pseudodisaccharide distribution depending on the caramel source: a D-fructose caramel contains prominent proportions of di-D-fructose dianhydrides, a D-glucose caramel mainly D-glucobioses, and a sucrose caramel similar proportions of both disaccharide/pseudodisaccharide series. It is noteworthy that di-D-fructose dianhydrides are found in all three types of caramels and might then be used as specific tracers of the authenticity of caramel, i.e., a product resulting from the controlled heat treatment of food-grade carbohydrates for use as food additives.
Acid hydrolysis of cell wall-rich material from thalli of the hornwort Anthoceros caucasicus yielded substantial amounts of an unusual disaccharide (1). Hydrolysis of 1 yielded only GlcA, Gal and unhydrolysed 1. Compound 1 was identified as alpha-D-GlcpA-(1-->3)-L-Gal by 1H and 13C NMR spectroscopic analysis and by the susceptibility of its monosaccharide units to phosphorylation by enantiomer-specific kinases. Compound 1 was not detected in acid hydrolysates of other land plants including mosses, leafy and thalloid liverworts, lycopodiophytes and euphyllophytes; it was also absent from charophytes. The Anthoceros polysaccharide that yields 1 was partially extractable in cold aqueous buffer (pH 4.7) and Na(2)CO(3), but not in EDTA or NaOH, suggesting that it was not a typical pectin or hemicellulose. The yield of 1 from various polysaccharide fractions correlated with the yields of Xyl, suggesting a previously unreported polymer containing D-GlcA, L-Gal and Xyl. The existence of a unique polysaccharide in an evolutionarily isolated plant (Anthoceros) supports the view that major steps in plant phylogeny were accompanied by significant changes in cell wall composition.
The alpha-glucosidase specific for the hydroxylysine-linked disaccharide units of collagens (or 2-0-alpha-D-glucopyranosyl-5-0-beta-D-galactopyranosylhydroxy-L-lysine glucohydrolase) has been measured in kidney cortex and brain cortical tissue of streptozotocin diabetic rats after 19, 23 or 28 weeks of diabetes and of aged rats 22 months old. Increased specific activities of the enzyme have been found repeatedly in the dialyzed homogenates and the 7.2 X 10(6) g.min supernatants of kidney and brain at the various stages of diabetes when compared with age-matched controls; the specific activities returned to a normal level after insulin treatment. Similar increased specific activities were observed in kidney and brain of the aged normoglycemic rats when compared with young adult rats. In diabetic kidney cortex, beta-galactosidase and p-nitrophenyl-alpha-D-glucoside glucosidase specific activities were decreased in contrast to the increase of glucosyl-galactosyl-hydroxy-lysine glucohydrolase. In kidney cortex of the aged rats, beta-galactosidase activity was also decreased, but p-nitrophenyl-alpha-D-glucoside glucosidase was increased. In both diabetic and aged rats, thickening of the kidney glomerular basement membranes was confirmed; thickening of the brain cortical capillary basement membranes was also observed. Thus in the diabetic and aged animals, the increased glucosyl-galactosyl-hydroxylysine glucohydrolase specific activity was associated with basement membrane thickening in the kidney and the brain.
We report the discovery of Eryloside F, a novel disaccharide of the steroidal carboxylic acid penasterol, isolated from an extract of the marine sponge Erylus formosus. The compound is a potent thrombin receptor antagonist, and furthermore inhibits human platelet aggregation in vitro.
Trehalose is a disaccharide present in a variety of anhydrobiotic organisms which have the ability to promptly resume their metabolism after addition of water. It has been successfully used as a nontoxic cryoprotectant of enzymes, membranes, vaccines, animal and plant cells and organs for surgical transplants. It has been predicted that trehalose can also be used as an ingredient for dried and processed food. Therefore, the recent biotechnological applications of trehalose have imposed the standardization of methods for its production, as well as for its specific quantification.
A gemini surfactant is an amphiphile possessing (in sequence) the following: hydrocarbon tail/polar group/spacer/polar group/hydrocarbon tail. Widespread interest in geminis has emerged recently from both industrial and academic laboratories. In the present contribution, two related families of geminis have been synthesized, both with trehalose, a disaccharide, as a polar spacer. One family, Series-A, is nonionic and has amide groups separating the long chains from the trehalose spacer. The other family, Series-B, has quaternary ammonium ions connecting the long chains to the trehalose spacer. It was found that Series-A geminis are water insoluble despite the two amides and multiple hydroxyls. When hydrated or extruded, these geminis form microscopically visible vesicular and tubular structures above their transition temperatures (which were determined calorimetrically). Insoluble monomolecular films, constructed from these geminis, have interfacial areas that are dominated by the sugar spacer although intermolecular chain/chain interactions seem to stabilize the films. Thus, the behavior of Series-A geminis in many ways parallels that of phospholipids and simple double-chain surfactants. It is as if the trehalose is less of a spacer than a large but conventional headgroup. In contrast, cationic Series-B geminis are water soluble and form micelles with critical micelle concentrations an order of magnitude lower than that of corresponding conventional surfactants. Molecular modeling using the Amber force field explains the difference in properties between the two families of geminis. Series-A are tubular in shape and thus prefer bilayer packing as do other amphiphiles in which the headgroups are similar in width to the sum of the tail diameters. Series-B geminis are conical-shaped and pack more readily into spherical micelles. This work entails synthesis, tensiometry, conductance, microscopy, surface balance studies, calorimetry, light scattering, and molecular modeling. In colloid chemistry, a balanced perspective cannot be achieved by one methodology alone but only through the pursuit of consilience among multiple approaches.
A series of 33 N-(2-chloroethyl)-N-nitrosocarbamoyl derivatives of N-substituted glycosylamines has been prepared and tested for antitumor activities. The compounds were obtained by reaction of glycosylamines with isocyanate, followed by nitrosation with N2O4. Structure-activity relationships of these trisubstituted nitrosoureas were investigated by varying the N-substituents and disaccharide groups and by comparing them with the corresponding disubstituted analogues. A large number of the nitrosoureas bearing a maltosyl group exhibited strong antitumor activities against leukemia L1210 and Ehrlich ascites carcinoma, and 60-day survivors against leukemia L1210 were found at the optimal dose for these derivatives. In contrast, the lactosyl and the melibiosyl derivatives were almost inactive. The most interesting compound in this series, the 3-isobutyl-3-maltosyl derivative (37), was tested against leukemia L1210 by single and multiple treatment. Its therapeutic ratio (96.3) obtained by multiple treatment is 3 times larger than that (31.5) obtained by single treatment, suggesting a possible clinical utility of 37 by multiple treatment. The favorable effect of a maltosyl moiety in this class of compounds is discussed.
Whether carbohydrate malabsorption causes diarrhea probably depends on the balance between the osmotic force of the carbohydrate and the compensatory capacity of the colon to dispose of the carbohydrate by bacterial fermentation. The present study evaluated the specific role of the osmolarity by comparing the severity of diarrhea after ingestion of two nonabsorbable carbohydrates, the fructooligosaccharide Idolax and the disaccharide lactulose. Both carbohydrates are readily fermented by the colonic flora but differ in osmolarity, the osmotic force being twice as high for lactulose as for Idolax. Twelve subjects were given increasing doses (0, 20, 40, 80, 160 g/d) of Idolax and lactulose in a crossover design. Every dose level was administered for three days with intervals of one week. Stools were collected on the third day to determine 24-hr volume, concentrations of short-chain fatty acids, L- and D-lactate, residues of Idolax or lactulose, sodium, potassium, pH, osmolarity, and in vitro productions of organic acids. Measured by short-chain fatty acid and lactate formation in a fecal incubation system, the fermentation of Idolax and lactulose was identical and very rapid compared with a range of reference carbohydrates. A laxative effect of both Idolax and lactulose was demonstrated. The increment in fecal volume as a function of the dose administered was twice as high for lactulose (slope of the regression line = 7.3, r = 0.64, P< 10(-5)) as for Idolax (slope = 3.7, r = 0.51, P<10(-3)), i.e., isosmolar doses of lactulose and Idolax had the same effect on fecal volume. The variation in fecal volume was substantial (lactulose 80 g/day: 110-1360 g/day; Idolax 160 g/day: 130-1440 g/day). High responders had earlier and larger fecal excretions of the saccharide compared with low-responders. Fecal volume in carbohydrate-induced diarrhea is proportional to the osmotic force of the malabsorbed saccharide, even though all or the majority of the saccharide is degraded by colonic bacteria. The capacity to modify the diarrhea varies considerably from person to person and is associated with colonic saccharide disposal, whereas the variation in response to isosmolar amounts of different saccharides is small within the same individual.
Aniline azopigments B4, B5 and B6, derived from conjugates of bilirubin-IX alpha in human bile, and previously characterized as disaccharidic esters [Kuenzle (1970) Biochem. J. 119, 387-394 and 411-435], were analysed by using t.l.c. and mass spectrometry. The compounds were identified as partially separated mixtures of 2-, 3- and 4-O-acylglucuronide positional isomers. The 1-O-acylglucuronide was not detected in the mixtures and was the only compound hydrolysed with beta-glucuronidase. Further scrutiny of structural assignments made by Kuenzle [(1970) Biochem. J. 119, 411-435] led to identification of the lactone and hexuronic acid derivatives that were obtained from azopigment B5 along with glucuronolactone and glucuronic acid. A branched-chain structure, i.e. 3-C-hydroxy-methyl-D-riburonic acid, was assigned previously, but the derivatives have now been identified as various incompletely silylated forms of glucuronolactone and glucuronic acid. Several trimethylsilyl derivatives glucuronolactone were isolated and characterized by n.m.r. and mass spectrometry.
The present work aims at evidencing the "kosmotrope" nature of trehalose through the analysis of inelastic neutron scattering measurements on trehalose and sucrose water solutions at different temperatures. Neutron spectra were collected by using the spectrometer MARI at the ISIS pulsed neutron source of the Rutherford Appleton Laboratory (Chilton, UK). To study the structural modifications induced on the tetrahedral hydrogen-bond network of water by homologous disaccharides, as a first step, the vibrational properties of pure water at different temperatures have been investigated. In particular, the temperature behavior of the intramolecular OH stretching mode has been analyzed. Successively, the vibrational properties for pure water have been compared with those of the sugar water solutions focusing the attention on the tetrahedral network-forming tendency. Finally, the obtained findings have been compared with previous Raman scattering evidences, and the results interpreted in the frame of recent molecular dynamics simulation works.