Polysaccharase metabolism in dormant and germinating Stylosanthes humilis seeds

The levels of certain polysaccharase and glycosidase enzymes were followed during the germination of Townsville stylo seeds. Significant levels of inve     

The structure of lannea coromandelica gum

Lannea coromandelica trees exude a water-soluble gum polysaccharide containing galactose (70%), arabinose (11%), rhamnose (2%), and uronic acids (17%). Three aldobiouronic acids are present (chromatographic analysis), namely 4-O-(α-d-galactopyranosyluronic acid)-d-galactose, 6-O-(β-d-glucopyranosyluronic acid)-d-galactose, and 6-O-(4-O-methyl-d-glucopyranosyluronic acid)-d-galactose. Linkage analysis of degraded gum A, obtained by controlled, acid hydrolysis, gave (chromatographic analysis) 3-O-β-l-arabinofuranosyl-l-arabinose, 3-O-β-l-arabinopyranosyl-l-arabinose, 3-O-α-d-galactopyranosyl-l-arabinose, 3-O-β-d-galactopyranosyl-d-galactose, and 6-O-β-D-galactopyranosyl-d-galactose. Degraded gum A was examined by methylation analysis, and was subjected to a Smith-degradation, giving degraded gum B, which was studied by linkage and methylation analysis. The O-methyl derivative of the whole gum was prepared by the Haworth and Purdie procedures and examined, after methanolysis, by g.l.c.: 2,3,4-tri-O-methyl-l-rhamnose, 2,3,5- and 2,3,4-tri- and 2,5-di-O-methyl-l-arabinose; 2,3,4,6-tetra-, 2,3,6-, 2,4,6-, and 2,3,4-tri-, and 2,6- and 2,4-di-O-methyl-d-galactose; 2,3,4-tri-O-methyl-d-glucuronic acid and 2,3,4-tri-O-methyl-d-galacturonic acid were identified. The whole gum was subjected to three successive Smith-degradations, giving Polysaccharides I–III which were examined by linkage and methylation analysis. The structural evidence obtained indicates that the gum molecules are very highly branched, based on a galactan framework consisting of short chains of β-(1→3)-linked d-galactose residues, branched and interspersed with β-(1→6) linkages. To positions 3 and 6 of this framework are attached either single d-galactose end-groups or short side-chains of d-galactose or of l-arabinose residues, and three aldobiouronic acids. The structure therefore appears to be very similar to that established recently for Lannea humilis gum.     

The structure of the neutral polysaccharide gum secreted by Rhizobium strain cb744

A previous investigation of the structure of the extracellular polysaccharide gum from the nitrogen-fixing Rhizobium strain cb744 (a member of the slow-growing Cowpea group) indicated that there were two β-(1→4)-linked d-glucopyranosyl residues for each α-(1→4)-linked d-mannopyranosyl residue, and that each mannose was substituted at O-6 by a β-d-galactopyranosyl residue having 71% of the galactose present as 4-O-methylgalactose. The present study shows that, although the gum appeared to have a simple tetrasaccharide repeating unit, it is composed of two closely associated components. One is a (1→4)-linked α-d-mannan substituted at each O-6 by a β-d-galactopyranosyl residue (71% 4-O-methylated). The second component is a (1→4)-linked β-d-glucan. The existence of the two polysaccharides was established by separation of the β-d-galactosidase-treated gum on a column of concanavalin A-Sepharose 4B. The d configurations were determined and the anomeric attribution of the linkages confirmed by the use of enzymes. The interaction between the two gum components is discussed.     

Structural investigation on degraded Spondias dulcis gum

Autohydrolysis of an aqueous solution of purified, exudate gum from Spondias dulcis trees yielded a degraded gum containing d-galactose, l-arabinose, and d-galacturonic acid in the mole ratios of 3:3:1. Methylation studies were conducted on the degraded gum and its carboxyl-reduced derivative. Three neutral and three acidic oligosaccharides were obtained on graded hydrolysis of the degraded gum, and these were characterized. Based on the results, a tentative structure was proposed for the repeating unit in the polysaccharide. The results of periodate oxidation supported the structure assigned. The anomeric configurations of the sugar residues were determined by studies of oxidation with chromium trioxide.     

Structural and immunochemical studies on Pterospermum suberifolium gum

The water-soluble polysaccharide from Pterospermum suberifolium gum is composed of l-rhamnose (24.0%), d-glucose (5.6%), d-galacturonic acid (32.4%), and d-glucuronic acid (19.7%), and it precipitated 77% of the antibody nitrogen from anti-Pneumococcal Type XXIII serum. From the results of methylation, periodate oxidation, and partial hydrolysis studies on the gum and its carboxyl-reduced product, a structure was assigned to its repeating unit. Inhibition of the cross-precipitation using the monosaccharides and the oligosaccharides obtained from the polysaccharide indicated that l-rhamnose and d-glucose were immunospecific, the former to the greater extent.     

Structural features of the gum exudates from some Acacia species of the series Phyllodineae and Botryocephalae

Smith degradation of each of the polydisperse, gum polysaccharides from Acacia pycnantha, A. difformis, A. filicifolia, and A. podalyriaefolia, for which molecular-weight distributions have been measured by gel-permeation chromatography, gives, in good yield, a methanol-insoluble polysaccharide that shows a single peak on examination by this technique. The molecular weights of the Smith-degraded polysaccharides are close to the values expected if the respective gum polysaccharides, on losing periodate-vulnerable, peripheral sugar residues were to be split also at regular intervals between the otherwise (1→3)-linked d-galactose chains. The structures of these gums, which are similar in many respects, conform to the pattern shown recently to occur in the gum of A. baileyana.     

Structural studies of sapote (Sapota achras) gum

Sapote gum contains residues of L-arabinose (pyranose and furanose), D-xylose, D-glucuronic acid, and 4-O-methyl-D-glucuronic acid in the ratio 1.0:2.8:0.48:0.52. The two uronic acids were conveniently determined by reducing the carboxyl functions with lithium borohydride and measuring the ratio of D-glucose to 4-O-methyl-D-glucose. Periodate oxidation of the carboxyl-reduced gum gave inter alia 2-O-methyl-D-erythritol and 4-O-methyl-D-glucose in amounts suggesting that 37% of the 4-O-methyl-D-glucuronic acid residues are unsubstituted in the polysaccharide. Acetolysis of the carboxyl-reduced gum gave O-α-D-glucopyranosyl-(1→2)-(4-O-β-D-xylopyranosyl)_0,1,2,-D-xylose, a hitherto undescribed series of oligosaccharides, together with 2-O-(4-O-methyl-α-D-glucopyranosyl)-D-xylose. Methylation confirmed that sapote gum has a highly branched structure, and commercial xylanases did not depolymerize the gum. An α-L-arabinofuranosidase liberated a substantial part of the arabinose residues. Sapote gum is a member of the uncommon class of plant gums having a D-xylose backbone and structurally resembles brea gum.     

Graded-hydrolysis studies on bael (aegle marmelos) gum

Graded hydrolysis of purified bael gum afforded three neutral and two acidic oligosaccharides, together with monosaccharides. These sugars were identified through periodate oxidation, methylation, reduction with lithium aluminum hydride, co-chromatography, and preparation of crystalline derivatives. The neutral oligosaccharides were characterized as 3-O-β-D-galactopyranosyl-L-arabinose, 5-O-β-D-galactopyranosyl-L-arabinose, and 3-O-β-D-galactopyranosyl-D-galactose, and the acidic oligosaccharides as 3-O-(β-D-galactopyranosyluronic acid)-D-galactose and 3-O-(β-D-galactopyranosyluronic acid)-3-O-β-D-galactopyranosyl-D-galactose.     

Composition and structure of whey protein/gum arabic coacervates

Complex coacervation in whey protein/gum arabic (WP/GA) mixtures was studied as a function of three main key parameters: pH, initial protein to polysaccharide mixing ratio (Pr:Ps)(ini), and ionic strength. Previous studies had already revealed under which conditions a coacervate phase was obtained. This study is aimed at understanding how these parameters influence the phase separation kinetics, the coacervate composition, and the internal coacervate structure. At a defined (Pr:Ps)(ini), an optimum pH of complex coacervation was found (pH(opt)), at which the strength of electrostatic interaction was maximum. For (Pr:Ps)(ini) = 2:1, the phase separation occurred the fastest and the final coacervate volume was the largest at pH(opt) = 4.0. The composition of the coacervate phase was determined after 48 h of phase separation and revealed that, at pH(opt), the coacervate phase was the most concentrated. Varying the (Pr:Ps)(ini) shifted the pH(opt) to higher values when (Pr:Ps)(ini) was increased and to lower values when (Pr:Ps)(ini) was decreased. This phenomenon was due to the level of charge compensation of the WP/GA complexes. Finally, the structure of the coacervate phase was studied with small-angle X-ray scattering (SAXS). SAXS data confirmed that at pH(opt) the coacervate phase was dense and structured. Model calculations revealed that the structure factor of WP induced a peak at Q = 0.7 nm(-1), illustrating that the coacervate phase was more structured, inducing the stronger correlation length of WP molecules. When the pH was changed to more acidic values, the correlation peak faded away, due to a more open structure of the coacervate. A shoulder in the scattering pattern of the coacervates was visible at small Q. This peak was attributed to the presence of residual charges on the GA. The peak intensity was reduced when the strength of interaction was increased, highlighting a greater charge compensation of the polyelectrolyte. Finally, increasing the ionic strength led to a less concentrated, a more heterogeneous, and a less structured coacervate phase, induced by the screening of the electrostatic interactions.     

The genetic structure of the A mating-type locus of Lentinula edodes

The Shiitake mushroom, Lentinula edodes (Berk.) Pegler is a tetrapolar basidiomycete with two unlinked mating-type loci, commonly called the A and B loci. Identifying the mating-types in shiitake is important for enhancing the breeding and cultivation of this economically-important edible mushroom. Here, we identified the A mating-type locus from the first draft genome sequence of L. edodes and characterized multiple alleles from different monokaryotic strains. Two intron-length polymorphism markers were developed to facilitate rapid molecular determination of A mating-type. L. edodes sequences were compared with those of known tetrapolar and bipolar basidiomycete species. The A mating-type genes are conserved at the homeodomain region across the order Agaricales. However, we observed unique genomic organization of the locus in L. edodes which exhibits atypical gene order and multiple repetitive elements around its A locus. To our knowledge, this is the first known exception among Homobasidiomycetes, in which the mitochondrial intermediate peptidase (mip) gene is not closely linked to A locus.     

The structure of elasterol from Ecballium elaterium

The structure of elasterol, the major sterol of Ecballium elaterium, is revised to (24S)-24-ethyl-5α-cholesta- 7,22,25-trien-3β-ol from 24-ethyl-5α-cholesta-7,16,25-trien-3β-ol.     

The structure of Klebsiella serotype 11 capsular polysaccharide

Using periodate oxidation, methylation analysis, the characterization of oligosaccharides obtained by partial acid hydrolysis, p.m.r. spectroscopy, and analytical ultracentrifugation, the structure of the (mildly alkali-treated) Klebsiella serotype 11 capsular polysaccharide has been elucidated. The tetrasaccharide repeating-unit comprises the sequence ?3)-β-D-Glcp-(1?3)-β-D-GlcUAp-(1?3)-α-D-Galp-(1→ with a 4,6-O-(1-car?yethylidene)-α-D-galactosyl residue linked to O-4 of the glucuronic acid residue. The structural basis for some serological cross-reactions of the Klebsiella K11 antigen is discussed, and it is shown that rabbit antisera against the Klebsiella K11 test-strain predominantly contain K agglutinins specific for branch-terminal 4,6-O-(1-car?yethylidene)-D-galactose.     

The structure of a mannitol teichoic acid from Bifidobacterium bifidum ssp. Pennsylvanicum

The isolation and analysis of the cell wall and cell wall fractions of Bifidobacterium bifidum ssp. pennsylvanicum are presented. With lysozyme a solubilized cell wall fraction is obtained which contains muramic acid, glucosamine, rhamnose, glucose, mannitol, phosphate and all peptidoglycan amino acids. Its composition did not change with culture age. A glycogen-like glucose polymer which is of cytoplasmic origin is identified in the insoluble cell wall fraction. The solubilized cell wall fraction contains a glucosylated rhamnose polymer which is linked by glycosidic bonds to the peptidoglycan fragments. This polymer is a 1,2-linked or an alternating, 1,2/1,3-linked α-rhamnose chain substituted on average at every second rhamnose residue with an α-linked glucose molecule. Various experiments gave evidence that mannitol and phosphate are present in 4,6-linked mannitol phosphate oligomers which are linked by phosphodiester bonds to the glucosylated rhamnose polymer. These oligomers may fulfill the functions of the more common wall teichoic acids.     

Alkaloids of Lycopodium paniculatum: The structure of paniculine

Three new alkaloids isolated from Lycopodium paniculatum were identified as paniculine (7α-hydroxy-acetyldihydrolycopodine), deacetylpaniculine and anhydrodeacetylpaniculine. Other known alkaloids isolated include flabellidine, lycoclavine, together with deacetyllycoclavine previously obtained as a degradation product of lycoclavine.     

The crystal structure of Echinococcus granulosus fatty-acid-binding protein 1

We describe the 1.6 Å crystal structure of the fatty-acid-binding protein EgFABP1 from the parasitic platyhelminth Echinococcus granulosus. E. granulosus causes hydatid disease, which is a major zoonosis. EgFABP1 has been implicated in the acquisition, storage, and transport of lipids, and may be important to the organism since it is incapable of synthesising most of its lipids de novo. Moreover, EgFABP1 is a promising candidate for a vaccine against hydatid disease.The crystal structure reveals that EgFABP1 has the expected 10-stranded β-barrel fold typical of the family of intracellular lipid-binding proteins, and that it is structurally most similar to P2 myelin protein. We describe the comparison of the crystal structure of EgFABP1 with these proteins and with an older homology model for EgFABP1.The electron density reveals the presence of a bound ligand inside the cavity, which we have interpreted as palmitic acid. The carboxylate group of the fatty acid interacts with the protein's P2 motif, consisting of a conserved triad R…R-x-Y. The hydrophobic tail of the ligand assumes a fairly flat, U-shaped conformation and has relatively few interactions with the protein.We discuss some of the structural implications of the crystal structure of EgFABP1 for related platyhelminthic FABPs.     

The crystal structure of arginyl-tRNA synthetase from Homo sapiens

Arginyl-tRNA synthetase (ArgRS) is a tRNA-binding protein that catalyzes the esterification of l-arginine to its cognate tRNA. l-Canavanine, a structural analog of l-arginine, has recently been studied as an anticancer agent. Here, we determined the crystal structures of the apo, l-arginine-complexed, and l-canavanine-complexed forms of the cytoplasmic free isoform of human ArgRS (hArgRS). Similar interactions were formed upon binding to l-canavanine or l-arginine, but the interaction between Tyr312 and the oxygen of the oxyguanidino group was a little bit different. Detailed conformational changes that occur upon substrate binding were explained. The hArgRS structure was also compared with previously reported homologue structures. The results presented here may provide a basis for the design of new anticancer drugs, such as l-canavanine analogs.     

Ultrastructural study of Arcellites humilis Villar de Seoane and Archangelsky, 2008, from the Cretaceous of Patagonia,Argentina

A scanning and transmission electron microscopy-based ultrastructural study of Arcellites humilis Villar de Seoane and Archangelsky, 2008, from the Kachaike Formation and Piedra Clavada Formation (Albian-Cenomanian) from several localities in Patagonia (Argentina), is presented in this paper. TEM-photographs of thin-sectioned specimens show a thick spore body wall composed of three layers: a thin and dense exine, an inner granular perine sublayer with irregularly disposed small channels and lacunae, and an outer alveolate perine sublayer with channels perpendicular to the external surface. Transverse sections of the A. humilis wall are compared with fossil and extant species of Marsileaceae. We show that the wall ultrastructure is similar in A. humilis, A. santacrucensis, A. disciformis, A. stellatus and Regnellidium upatoiensis. However, the body wall and acrolamella of A. humilis are more similar to those of R. diphyllum Lindman than to those of the Marsilea L. or Pilularia L. species. Water ferns such as members of the Marsileaceae played an important role in aquatic or semi-aquatic niches in Patagonian Cretaceous floras, suggesting that high humidity and temperature prevailed during the Albian-Cenomanian in this region of Argentina.     

Chemical investigations on the gum exudate from sajna (Moringa oleifera)

The purified, whole-gum exudate from the drum-stick plant (Moringa oleifera) was found to contain l-arabinose, d-galactose, d-glucuronic acid, l-rhamnose, d-mannose, and d-xylose in the molar ratios of ～ 14.5:11.3:3:2:1:1. A homogeneous, degraded-gum polysaccharide consisting of d-galactose, d-glucuronic acid, and d-mannose in the molar ratios of ～ 11.7:3.9:1, was obtained on mild hydrolysis of the whole gum with acid. Permethylation studies were conducted on the whole gum, the degraded gum, and their carboxyl-reduced products, and the results were in good agreement with those obtained from periodate oxidation followed by Smith degradation. Also, isolation and characterization of the oligosaccharides obtained from the mother liquor during preparation of the degraded gum, and by graded hydrolysis of the degraded gum, were achieved. On the basis of the results obtained from these studies, a tentative structure was assigned to the average repeating-unit of the gum.