Study of 1-deoxy-1-(indol-3-yl)-L-sorbose, 1-deoxy-1-(indol-3-yl)-L-tagatose,and their analogs

Alkaline degradation of the ascorbigen 2-C-[(indol-3-yl)methyl]-alpha-L-xylo-hex-3-ulofuranosono-1,4-lactone (1a) led to a mixture of 1-deoxy-1-(indol-3-yl)-L-sorbose (2a) and 1-deoxy-1-(indol-3-yl)-L-tagatose (3a). The mixture of diastereomeric ketoses underwent acetylation and pyranose ring opening under the action of acetic anhydride in pyridine in the presence of 4-dimethylaminopyridine (DMAP) with the formation of a mixture of (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-xylo-hex-1-enitol (4a) and (E)-2,3,4,5,6-penta-O-acetyl-1-deoxy-1-(indol-3-yl)-L-lyxo-hex-1-enitol (5a), which were separated chromatographically. Deacetylation of 4a or 5a afforded cyclised tetrols, tosylation of which in admixture resulted in 1-deoxy-1-(indol-3-yl)-3,5-di-O-tosyl-alpha-L-sorbopyranose (12a) and 1-deoxy-1-(indol-3-yl)-4,5-di-O-tosyl-alpha-L-tagatopyranose (13a). Under alkaline conditions 13a readily formed 2-hydroxy-4-hydroxymethyl-3-(indol-3-yl)cyclopenten-2-one (15a) in 90% yield. Similar transformations were performed for N-methyl- and N-methoxyindole derivatives.     

Effects of polyhydroxy compounds on the structure and activity of alpha-chymotrypsin

The effects of glycerol, polyethylene glycol, fructose, glucose, sorbitol, and saccharose on the conformation and catalytic activity of alpha-chymotrypsin were studied in 0.1 M sodium phosphate buffer and buffered aqueous 60% ethanol (pH 8.0). The enzyme activity was practically completely lost within 10 min in 60% ethanol, but in the presence of stabilizers the activity was retained. With the exception of polyethylene glycol, the stabilizing effect decreased with increase of the incubation time. The preservation of the catalytic activity was accompanied by changes in the secondary and tertiary structures of alpha-chymotrypsin.     

Water T2 relaxation in sugar solutions

1H spin-spin relaxation times of water were measured with the CPMG sequence in dilute aqueous solutions of glucitol, mannitol, glycerol, glycol, the methyl D-pyranosides of alpha-glucose, beta-glucose, alpha-galactose, beta-galactose, alpha-xylose, beta-xylose, beta-arabinose and sucrose, alpha,alpha-trehalose, beta-maltose, maltotriose and maltoheptaose. The relaxation-time dispersion was measured by varying the CPMG pulse spacing, tau. These data were interpreted by means of the Carver-Richards model in which exchange between water protons and labile solute hydroxyl protons provides a significant contribution to the relaxation. From the dependences on temperature and tau, parameters characteristic of the pool of hydroxyls belonging to a given solute were extracted by nonlinear regression, including: the fraction of exchangeable protons, P, the chemical-shift difference between water protons and hydroxyl protons, deltaomega, the intrinsic spin-spin relaxation time, T2, and the chemical exchange rate, k. These solute-specific parameters are related, respectively, to the concentration, identity, mobility and exchange life-time of the hydroxyl site. At 298 K, values of deltaomega, T2 and k were found to be of the order of 1 ppm, 100 ms and 1000 s(-1), respectively. Effects of molecular size, conformation and solute concentration were investigated. The exchange mechanism was characterised by Eyring activation enthalpies and entropies with values in the ranges 50-70 kJ mol(-1) and -10 to 60 J K(-1)mol(-1), respectively.     

Chronic exposure to soil salinity in terrestrial species: Does plasticity and underlying physiology differ among specialized ground-dwelling spiders?

In salt marshes, the alternation of low and high tides entails rapid shifts of submersion and aerial exposure for terrestrial communities. In these intertidal environments, terrestrial species have to deal with an osmotic loss in body water content and an increase in sodium chloride concentration when salt load increases. In salt marshes, spiders represent an abundant arthropod group, whose physiological ecology in response to variations of soil salinity must be further investigated. In this study, we compared the effect of salinity on the survival and physiology of three species of Lycosidae; two salt marsh species (Arctosa fulvolineata and Pardosa purbeckensis) and one forest species (P. saltans). Spiders were individually exposed at three salinity conditions (0‰, 35‰ and 70‰) and survival, changes in body water content, hemolymph ions (Na⁺, Ca²⁺, Mg²⁺, K⁺; ICP-MS technique) and metabolites (mainly amino acids, polyols, sugars; LC and GC techniques) were assessed. The survival of the forest species P. saltans was very quickly hampered at moderate and high salinities. In this spider, variations of hemolymph ions and metabolites revealed a quick loss of physiological homeostasis and a rapid salt-induced dehydration of the specimens. Conversely, high survival durations were measured in the two salt-marsh spiders, and more particularly in A. fulvolineata. In both P. purbeckensis and A. fulvolineata, the proportion of Na⁺, Ca²⁺, Mg²⁺, K⁺ remained constant at the three experimental conditions. Accumulation of hemolymph Na⁺ and amino acids (mainly glutamine and proline) demonstrated stronger osmoregulatory capacities in these salt-marsh resident spiders. To conclude, even if phylogenetically close (belonging to the same, monophyletic, family), we found different physiological capacities to cope with salt load among the three tested spider species. Nevertheless, physiological responses to salinity were highly consistent with the realized ecological niches of the spiders.     

Accumulation of Compatible Solutes in Penicillium frequentans Grown at Reduced Water Activity and Biocontrol of Monilinia laxa

The biocontrol fungus Penicillium frequentans was grown on potato dextrose broth of either - 0.4 MPa water potential (unstressed) or reduced water potential (stressed) media modified with glycerol to - 7.0 MPa. The endogenous compatible solutes and sugars were quantified after 5, 10 and 15 days growth. Glycerol was the main compatible solute accumulated at reduced water potential, with a concomitant decrease in erythritol and mannitol, and the sugar, glucose. Maximum accumulation of glycerol occurred in 5-day-old cultures, with the content in P. frequentans biomass produced at reduced water potential being about 180 times higher than that produced in unmodified medium (- 0.4 MPa). There was no enhanced accumulation of the desiccation protectant trehalose. Homogenisation of cultures, for spray applications of the fungus, resulted in a partial loss of the solutes accumulated in the fungal biomass. P. frequentans controlled peach brown rot ( Monilinia laxa ) on peach twigs, with the disease index being significantly smaller when treated with the antagonist produced at reduced water potential. However, both inoculum types were able to reduce the length of lesions to a similar extent. This suggests that the inoculum of the antagonist produced in medium with freely available water (- 0.4 MPa) becomes rapidly adapted to the dry environment in the phyllosphere, counteracting the possible initial advantage of the inoculum produced at reduced water potential (- 7.0 MPa).     

The joint action in the bioactivity studies of Antarctic lichen Umbilicaria antarctica: Synergic-biodirected isolation in a preliminary holistic ecological study

Antarctica is one of the world’s most inaccessible regions. This area is also unique in that it has a terrestrial biota dominated by non-vascular plants, of which lichens and mosses are typically the dominant life-forms. A phytochemical study of Antarctic lichen (Umbilicaria antarctica) collected from maritime Antarctica has been carried out. The hexane, acetone and butanol extracts have been subjected to a preliminary general bioactivity test using wheat etiolated coleoptiles. A chromatographic study of the acetone extract was performed and seven known compounds were isolated. The general bioactivity of the compounds on etiolated wheat coleoptile has been assessed and joint action studies on mixtures of the compounds were carried out − a methodology that may be the way to a holistic approach in the ecological studies of lichens. The results corroborated the activity exhibited by the original fractions, which in turn support the use of this bioassay to determine joint interactions responsible for the bioactivity shown by U. antarctica.     

Chitosan and gelatin based edible films: state diagrams, mechanical and permeation properties

Films of chitosan and gelatin were prepared by casting their aqueous solutions (pH≈4.0) at 60°C and evaporating at 22 or 60°C (low- and high-temperature methods, respectively). The physical (thermal, mechanical and gas/water permeation) properties of these composite films, plasticized with water or polyols, were studied. An increase in the total plasticizer content resulted in a considerable decrease of elasticity modulus and tensile strength (up to 50% of the original values when 30% plasticizer was added), whereas the percentage elongation increased (up to 150% compared to the original values). The low-temperature preparation method led to the development of a higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two orders of magnitude, of CO₂ and O₂ permeability in the chitosan/gelatin blends. An increase in the total plasticizer content (water, polyols) of these blends was found to be proportional to an increase in their gas permeability.     

Stress metabolites and their role in coastal plants

The stress metabolites proline, glycine betaine and sorbitol were accumulated in the leaves of some angiosperms from sand dunes and shingle. Chloride, where it was measured, was not accumulated to high concentrations in leaves suggesting that these soils are not saline. Sand dunes and shingle soils have low water-holding capacity, so it is possible that solute accumulation was a response to drought which could be of adaptive significance. In sand dunes low water availability could be associated with increased leaf temperatures because of reduced transpiration rates and high soil temperatures. The role of stress metabolites in heat tolerance was considered. Proline, betaine, sorbitol and mannitol increased the heat stability of glutamine synthetase (GS) and glutamate: oxaloacetate aminotransferase from Ammophila arenaria. For GS the effect increased with solute concentration. The polyols were more effective at high temperatures. The heat stability of GS from the moss Tortula ruraliformis and the brown alga Fucus vesiculosus was increased by mannitol. The effect of the solutes was independent of plant species and type of enzyme. It is suggested that the accumulation of solutes may have ecological importance in protecting sand-dune plants from heat damage during periods of drought.     

Changes in the fungus-specific,soluble-carbohydrate pool during rapid and synchronous ectomycorrhiza formation of Picea abies with Pisolithus tinctorius

A simple and convenient culture system has been developed for the analysis of ectomycorrhiza formation under controlled conditions. Rapid and synchronous mycorrhiza synthesis was observed when thin and even layers of Pisolithus tinctorius (Pers.) hyphae were brought at once into contact with the entire root system of 3-month-old Picea abies (L. Karst) plants. Suitable fungal layers were grown on cardboard with limiting glucose supply in the medium to maximize radial growth. The glucose was almost consumed by the time the fungus had spread over the whole cardboard and was ready for inoculation of the roots. At this stage, the fungus contained trehalose and arabitol as the main soluble carbohydrates. A few hours after the assembly of the culture system, contacts between roots and aerial hyphae were observed and a sheath was formed 3 days later, suggesting very rapid ectomycorrhiza formation under these conditions. The pool of soluble carbohydrates of the inoculum, i.e. the extramatrical mycelium, declined after inoculation of the roots and was almost zero after 2 weeks. The supply of carbon by the plant was then sufficient for the fungus to expand the soluble pool efficiently in both the mycorrhizas and the extramatrical mycelium. The kinetics of the carbohydrate pool and the observed differentiation of the short roots to mycorrhizas imply that in our culture system fully functional symbiosis was established no later than 14 days after the plants were inoculated with the fungus.     

Modeling and measurements of solid-liquid and vapor-liquid equilibria of polyols and carbohydrates in aqueous solution

The solubilities of five saccharides in water have been measured at various temperatures. This includes the monosaccharides xylose and galactose, and the disaccharides maltose monohydrate, cellobiose and trehalose dihydrate. A method that uses interaction energies and interaction parameters calculated with molecular mechanics methods has shown to give good predictions of the phase behavior of a variety of mixtures, including glycols and small saccharides in aqueous solution. The method is completely predictive, as the strength of the molecular interactions is determined with a theoretical method in the absence of any phase equilibrium data. For calculating solubilities, experimental values for the melting points and the heats of fusion of the compounds under study are, however, necessary. The solubilities of the five saccharides listed above, raffinose and meso-erythritol in water were calculated with this method. The calculated solubilities are in reasonably good agreement with experiment, and in the case of meso-erythritol, which is a polyalcohol (polyol), and galactose, the agreement between prediction and experiment is excellent. Also the vapor pressures of water over several polyols and saccharides in aqueous solution have been predicted with this method, giving results in excellent agreement with the experimental values.