Fernand Barnoud

Chemical and 13C N.M.R. studies on two arabinans from the inner bark of young stems of Rosa glauca

Abstract Two water-soluble arabinan fractions have been isolated from the inner bark of Rosa glauca stems. Methylation analysis and periodate oxidation revealed that the two polysaccharides have similar, highly branched structures consisting of α- L -arabinofuranose residues substituted (1→2), (1→3), and (1→5). The two arabinans differ in their degree of polymerization: 100 and 34, respectively. 13 C-N.M.R. spectroscopy has been used to distinguish between glycosidically substituted and free C-5 groups in the polymer, as well as to assign the methoxyl groups at positions 2, 3 and 5 of the methylated arabinans. The different types of linkages could also be identified. The results obtained by chemical N.M.R.-spectroscopic methods were in good agreement.

Characterization of structurally similar neutral and acidic tetrasaccharides obtained from the enzymic hydrolyzate of a 4-O-methyl-D-glucurono-D-xylan.

Abstract Two similar tetrasaccharides, one neutral and one acidic, were isolated from the products released by the attack of a xylanase on the in situ reduced 4- O -methyl- D -glucurono- D -xylan from aspen ( Populus tremuloides ). Paper chromatography, gel filtration behavior, methylation followed by reduction, and mass spectrometry showed that the oligosaccharides were O -(4- O -methyl-α- D -glucopyranosyluronic acid)-(1→2)- D -xylotriose and- O -(4- O -methyl-α- D -glucopyranosyluronic acid)-(1→2)- D -xylotriose. Independent of the acidic or neutral substituent on the present xylan chain, the enzymic cleavage led preferentially to oligosaccharides substituted at the nonreducing end. The existence, in wood, of a few uronic acid substituents of the D -xylan in the esterified form was confirmed, and their linkage to lignin postulated.

Hemicelluloses of Arundo donax at different stages of maturity

Abstract The hemicellulosic composition of the internodes of Arundo donax depends on the maturity of the tissue. The percentage of xylose in the total hemicellulose increases with increasing plant maturity. The main hemicellulose is an arabino-4-O-methyl glucurono xylan which is already present in the youngest tissues and has the same structural features regardless of the age of the tissues. The average D.P. of this polysaccharide increases from about 60 to 150 with maturation of the plant tissue.

The carbohydrate constituents of the cell wall of suspension cultures of Rosa glauca

Abstract Sequential extractions of 14-day-old Rosa glauca cell walls cultured in vitro showed that two different types of acidic polysaccharide were present. One was extracted with EDTA or ammonium oxalate solutions, and the other remained in close association with cellulose even after 4.3 N NaOH extractions or 2 N H 2 SO 4 hydrolysis. The cell wall has a low content in structural protein. The behaviour of each constituent sugar was followed during the course of the various extraction steps, and a complete quantitative account of the protein, uronic acid and neutral sugar components is given at each stage.

Callus formation and induction of a cell suspension culture from Acacia senegal

Cell proliferation has been induced from the cambial zone of a branch of Acacia senegal, kept on the basal Knop and Ball medium in the presence of auxin. Transferred on the more complete nutrient medium of Schenk and Hildebrandt, the colonies gave rise to several cell lines. One of the friable lines, consisting of aggregates of parenchymatous cells, gave a cell suspension culture in an agitated liquid medium which is maintained as a strain of illimited growth. The heterogeneous suspension did not undergo noticeable changes after eight transfers. Aggregates collected on a 1000-μm nylon seive were able to grow on a solid medium and gave back a friable callus similar to the initial colonies.

La D-xylane du roseau Arundo donax

Abstract An L -arabino- D -glucurono- D -xylan isolated from the mature stalk of the reed Arundo donax contained the neutral sugars D -xylose, L -arabinose, and D -glucose in molar proportions 8.9:1:traces. 2- O -(4- O -Methyl-α- D -glucopyranosiduronic acid)- D -xylose was also present. The results of methylation analysis showing the presence of 2,3,4-tri-, 2,3-di-, 2-, and 3- O -methyl- D -xylose together with 2,3,5-tri- O -methyl- L -arabinose were determined by the gas-liquid chromatography-mass spectrometry technique and were in good agreement with those of the periodate oxidation. The D -xylan has an average degree of polymerization of about 80 and is essentially linear. The polysaccharide has structural features similar to those of polysaccharides isolated from other Gramineae.

Hemicelluloses of young internodes of Arundo donax

Abstract An arabino 4- O -methyl glucurono xylan has been isolated as the dominant form of the hemicellulosic material of the youngest internodes of Arundo donax . The polysaccharide contained d -glucose, d -xylose and l -arabinose in the molar ratios of 0·1:9·2:0·66, respectively, with a uronic acid content of 4·5%. Methylation and periodate-oxidation showed that the xylan has a β-1 → 4-linked xylose backbone and a degree of polymerization ca. 63. The xylan is very similar to that found in the mature tissues.

Purification of cell-wall β-d-xylanases from Acacia cultured cells

Abstract An improved technique for the purification of β- d -xylanases from Acacia in vitro cultured cells is described, involving 4 M LiCl extraction anion-exchange chromatography, gel filtration chromatography and flat-bed electro-focusing steps. The procedure had been efficient since it resulted in preparations each containing a cell-wall xylanase with slight α-amylase and 1.4-β- d -glucanase contaminant activities. It also yielded a highly active homogeneous xylanase with a molecular weight of 55-kilodalton and an isoelectric point, pI of 5.70.

Wall-bound 1,3-β-d-glucan: Orthophosphate glucosyltransferase activity from acacia cultured cells

Abstract A wall-bound enzyme has been identified from Acacia verek suspended cells. It exhibited a 1,3-β- d -glucan: orthophosphate glucosyltransferase activity (EC 2.4.1.97), the characteristics of which are reported. In 50 mM citrate-phosphate buffer (pH 6.5), the phosphorolytic cleavage of laminarin and laminaribiose can be observed. In 0.2 M imidazole buffer (pH 6.5), the phosphorylase equilibrium lies in the direction of the synthesis reaction, α- d -glucose-1-phosphate as glucosyl donor being incorporated into a dimer laminaribiose. Glucose released from exo laminarinase activity (EC 3.2.1.58), similarly bound to cell walls, can compete phosphorylase action, suggesting that this has an in vivo regulatory role.

Changes of the cell wall carbohydrates in the internode of arundo donax (gramineae) at different stages of growth

Abstract The changes in the total hemicellulose and cellulose carbohydrate composition of the cell walls from the eight internodes constituting a 1-month-old culm of the reed Arundo donax have been examined. Similar changes were also studied at the level of one elongating internode. They are interpreted in terms of polysaccharide deposition in the cell wall of the fibres with maturation. A comparison of the polysaccharide distribution between parenchym and vascular bundles has been established. There is a relationship between the increase in xylose and glucose content, the decrease in arabinose and galactose content, together with the elongation of the fibres. Each internode appears as a physiological unit where the progressive fibrous character of the tissues corresponds to a characteristics cell wall polysaccharide composition.