Higher Uronic Acid Content Research Articles

Collagen and uronic acid distribution in the human sclera

In the normal adult eye the content of uronic acid, hydroxyproline, hydroxylysine and proline from different parts of sclera was examined. Scleral samples from the posterior eyeball showed a higher content of uronic acid than the scleral samples from papilla, equator and limbus. Apart from a lower concentration of hydroxyproline in sclera from equator, no major differences in concentration of hydroxyproline, hydroxylysine or proline was found in sclera samples.

Acacia gum exudates from somalia and tanzania: the Acacia senegal complex

Analytical data are presented for the polysaccharide and proteinaceous components of the gum exudates from three Somalian Acacia spp. viz. Acacia sp. nov. (Fagg & Styles 85) and A. cheilanthifolia Chiov. (members of the A. senegal complex) and A. leucospira Brenan. In addition, data are given for a Tanzanian specimen of gum arabic and, for comparative purposes, for a reference specimen of Sudanese gum arabic from A. senegal (L.) Willd. The gum from A, leucospira is dextrorotatory and has a low rhamnose, high uronic acid and high methoxyl content; it therefore has affinities to the sources of commercial gum talha ( A. seyal Del. and relatives). In contrast, the gums from A. cheilanthifolia and Acacia sp. nov. are laevorotatory and of special interest as they provide the first opportunity to study positively identified members of the A. senegal complex backed by properly documented herbarium voucher specimens. Although undoubtedly closely related species,their chemical and spectroscopic data indicate that their gum exudates, and that from the Tanzanian sample, are analytically and structurally distinct from that of A. senegal (L.) Willd.

Regional glycosaminoglycans composition of the human sclera

Human sclera from different parts of the normal adult eye was analyzed for content of uronic acid and the distribution of specific glycosaminoglycan types. Uronic acid is widely determined as representative of glycosaminoglycans in biological substances and variations of about 2-fold were found. Differences of up to 50% were detected in the relative abundance of hyaluronic acid and of dermatan sulphate, depending on the site on the globe from which the sample was taken. Sclera from around the papilla was found to be rich in content of dermatan sulphate. Sclera from the posterior eyeball showed a higher percentage of chondroitin sulphate as compared with sclera from equator and limbus. Equatorial sclera was richer in hyaluronic acid than posterior sclera. Sclera from the posterior eyeball showed a higher content of uronic acid as compared with sclera from equator and limbus. This work is an addition to the understanding of the scleral biochemistry and this finding may have some relevance in connection with ocular disease, as the proteoglycans and their content of glycosaminoglycans play a key role in the regulation of collagen fibril assembly and in the biomechanical strength of collagen fibrils.

Increase of Free Space Solutes in Tobacco Leaves in Relation to the Localized Cellular Response Following Injections of a Bacterial Protein‐Lipopolysaccharide Complex*

AbstractVariations in pH, cell ultrastructure, conductivity, calcium ion molarity, reducing sugars, uronic acids and in protein of the intercellular washing fluid were studied at 0, 12, 24 and 48 h in tobacco leaf halves intercellularly injected with a bacterial pr‐LPS complex (250 μg‐ml−1). These injections induced a localized cellular reaction (LCR) in points opposite to intercellular structured deposits on the plant cell walls. The intercellular fluid pH was higher at 24 h than in the control, but not at 12 and 48 h. The conductivity, the calcium ion molarity, the free and hydrolyzed sugar content were higher at 12, 24 and 48 h than in the control tissue; the uronic acid content was higher at 24 and 48 h, but not at 12 h. There was a peak for, all 5 parameters at around 24 h, when LCR showed its highest activity. The protein content was significantly higher at 24 and 48 h than in the control intercellular fluid.The increase in conductivity, calcium ions, sugar, uronic acids and proteins in the intercellular fluids of the pr‐LPS injected tissue were interpreted as direct or indirect effects of the LCR, i.e. as an exocytosis induced by pr‐LPS injections. The associated high sugar and uronic acid content of the intercellular fluid at 12 and 24 h was not correlated to its capacity to prevent the hypersensitive confluent necrosis when injected intercellularly into tobacco tissue.

Composition of the water-soluble polysaccharide isolated from the leaves of Cyclea burmanni

The water soluble polysaccharide isolated from the leaves of Cyclea burmanni sets to a firm jelly at room temperature. It contained a high proportion of uronic acids and a small amount of neutral sugars. Galactose and arabinose are the major neutral sugars present. The high uronic acid content and the distribution of neutral sugars in the polysaccharide and partial hydrolysates suggest that the water soluble polysaccharide is probably a rhamnogalacturonan.

The digestion of monosaccharide residues of the cell walls of oat and vetch hays by rumen contents in vitro

AbstractThe extent and pattern of digestion of oat hay (Avena sativa L.) and vetch hay (Vicia sativa L.) monosaccharides by rumen contents was studied in vitro. The ratios of matrix polysaccharides to lignin were 1.25:1 and 3.82:1 in the vetch and oat hays, respectively. Glucose, xylose and uronic acids were the main sugars in both plants, comprising about 90% of the total monosaccharides. Glucose, xylose and arabinose were mainly confined to the cell walls (CW), whereas galactose and uronic acids were found in high proportions in the soluble fraction. Vetch had a particularly high uronic acid content (14.4 g 100 g−1 DM), of which 71% was pectic material. The ratios of CW‐glucose to CW‐xylose were 2.23:1 and 3.74:1 in the oat CW and vetch CW, respectively. Based on monosaccharide analyses of the CW material, it is suggested that the degree of branching of the matrix polysaccharides is about twice as high in vetch as in oat hay. Total glucose and xylose were more digestible in oat than in vetch hay, whereas most of the minor sugars and the total uronic acids were more digestible in the vetch. Irrespective of species, CW glucose was more digestible than CW xylose. The digestibilities of CW glucose, CW xylose and CW uronic acid were: 61.0, 55.3, 51.5, 34.3 and 62.7, 42.6 for the oat hay and vetch hay, respectively. Following the pattern of digestion, CW arabinose and CW glucose were digested faster than CW xylose and CW uronic acid, irrespective of plant species. The extent of digestion at 12 h of incubation of these sugars was higher in vetch than in oat hay. It is suggeted that the concentration ratio of rapidly to slowly degradable CW sugars, in a given plant, is a major determinant of the rate of CW digestion by rumen microorganisms.

Effect of ozone and sodium hydroxide treatments on some chemical characteristics of cotton straw

AbstractCotton straw (CS) was treated with ozone or sodium hydroxide, and the effect of treatments on the organic acid and monosaccharide composition and on the chromat‐ographic characteristics of alkali lignin was studied. The concentrations of formic and acetic acids in the ozonised CS were 3.98 and 1.36 g 100 g−1 organic matter (OM) respectively. Oxalic acid was not detected. A high content of uronic acids (9.78 g 100 g−1 OM) was found in CS. The overall decrease in total monosaccharides in the ozonated CS was very small (5%) with the matrix constituents being principally affected. The 8% sodium hydroxide treatment exerted a very limited effect on the composition of CS cell walls. Ozonation increased the content of soluble carbohydrates from 9.2 to 21.8%; this was contributed mainly by the hemicellulose fraction. Alkali lignin was extracted from CS and was fractionated by gel chromatography. The elution pattern of alkali lignin was very similar for the treated and untreated materials. The three peaks coincided at an average mol. wt of 40 000, as judged from the use of dextran standards.

Some observations on the calcium ion binding to the eggshell matrix.

The calcified matrix of the hen eggshell has been demineralized with the EDTA. Aliquots of this material are soluble in water and have been characterized by column chromatography and by chemical analyses. Of particular interest is the high hexosamine and uronic acid content, which confirms the protein-polysaccharide nature of this water-soluble material. The calcium ion binding to the eggshell matrix has been studied by the equilibrium dialysis technique at different pH values, with both free and blocked carboxylic groups. The material with the free carboxylic side chain groups binds more calcium ions with increasing pH value. When the carboxylic groups have been previously blocked with a water-soluble carbodiimide, the calcium ion binding rapidly decreases. The residual capacity to bind calcium ions in the material with the carboxylic functions modified is probably due to the sulfate ions. In agreement with previous observations on other calcified substrates, the calcium ion binding seems to depend on the presence of ionized carboxylic functions of the matrix.

Cartilage proteoglycans and calcification

Calcifiable matrices of scapula cartilage and nasal septum, a non-mineralizing tissue, have been analyzed in parallel to compare their composition and some biochemical properties. The results obtained have shown that the two tissues present the following differences: 1. (i) the guanidinium extract from nasal septum has a higher content of uronic acid than the extract from scapula cartilage; 2. (ii) the distribution of nasal proteoglycans in the fractions obtained by spinning the extract in CsCl density gradients is different from that of scapula proteoglycans; 3. (iii) a glycoprotein endowed with Ca 2+ affinity is present in the two tissues. However, the glycoprotein extracted from nasal septum lacks the high-affinity binding sites of the scapula cartilage glycoprotein; 4. (iv) proteoglycans from nasal septum show higher inhibition of the rate of formation of crystalline calcium phosphate in vitro than those from scapula cartilage.

Polysaccharide and oligosaccharide changes in germinating lupin cotyledons

In germinating lupin cotyledons, there was a rapid depletion of raffinose series oligosaccharides, a temporary increase in sucrose and constant low levels of reducing monosaccharides. The major polysaccharide fraction was extracted with hot NH4 oxalate—EDTA solution and had the constitution of intercellular/cell wall polysaccharide. GLC examination of component sugars showed that as cotyledons expanded this fraction was depleted and that there was selective hydrolysis of arabinose and galactose, so that the uronic acid proportion increased. Gel and DEAE-cellulose chromatography showed that this fraction became more heterogeneous. The neutral and acidic fractions were separated and the component sugars, viscosities, gel chromatographic behaviour and sedimentation constants of these determined. The results indicated that in the later phase of plant cell wall expansion in germinating lupin cotyledons the arabinogalactan side chains of the pectic polysaccharide fraction are selectively hydrolysed leaving a primary wall with a high uronic acid content.

Carbohydrates of the brown seaweeds himanthalia lorea and bifurcaria bifurcata: Part II. structural studies of the “fucans”

Methylation, periodate oxidation, and partial hydrolysis studies have revealed the essential similarity of the different fucose-containing polysaccharides separated from the title algae. The high-fucose, high sulphate-containing material more closely resembles the fucan reported in the literature and has (1→2)- and (1→3)-linked fucose residues with sulphation at C-4. The glucuronic acid and xylose residues are not sulphated and are on the periphery of highly branched molecules. In the polysaccharide having a high content of uronic acid, the fucose residues are similarly linked, and again the xylose and a large proportion of the glucuronic acid residues are present as end-group and (1→4)-linked units on the outside of the highly branched molecules. Partial hydrolysis studies proved the mutual linkage of the fucose (at C-3) and glucuronic acid, and the presence of an unidentified 6-deoxy sugar derivative which was also linked to glucuronic acid. Selective cleavage of the glucosiduronic acid linkages by Hofmann degradation of the amide derivative was unsuccessful.

Fractionation and characterisation ofj water‐soluble polysaccharide‐protein complexes containing hydroxyproline from the leaves of Vida faba

AbstractThe water‐soluble polysaccharide‐protein complexes obtained previously by extraction with aqueous trichloroacetic acid and by phenol‐aqueous (pH 8) partitioning from the leaves of Vicia faba were fractionated into a number of components by continuous high voltage electrophoresis at pH 8.3 and 3.97 and by Sepharose 4B chromatography. The results indicated that these materials contained a spectrum of molecules with rather similar properties. All fractions obtained contained about 4–7% (wlw)lightly bound protein, two‐thirds of which was made up of four amino acids: hydroxyproline, alanine, serine and threonine. Similarly, all materials contained uronic acid (10–70%; w/w)and neutral sugars (10–90%; w/w), mainly arabinose and galactose. High uronic acid content was found to be associated with appreciable rhamnose content and an arabinose‐galactose ratio close to 2. This ratio became about 0.3 when the amount of uronic acids decreased to about 10% (w/w).

Brightness reversion of birch sulfate pulp

AbstractThree methods of improving brightness stability have been examined: (1) Avoidance of chlorination of extractive components and the residual resin. (2) Modification of the hemicellulose by high‐temperature treatment of the pulp to remove xylan components of poor brightness stability. (3) Maximum reduction of the residual lignin in the pulp. The results of the three methods have been compared and an examination of their combined effect has thrown light on the main cause of brightness reversion in each case. The chlorinated extractives adversely affect the brightness stability during aging in a dry atmosphere, and the reversion in this case is due to degradation mainly of carbohydrates by the hydrogen chloride liberated from the chlorinated extractives. Different fractions of the extractives have been tested with respect to their ability to promote this effect. It would seem that the brightness stability of the pulp is dependent on its carbohydrate composition. An aqueous treatment of the pulp at a high temperature removes some hemicellulose components sensitive to reversion (particularly xylan, which has a high content of uronic acid). Under moist conditions, the hydrochloric acid released from the extractives is diluted and thus has much less influence on the degradation of the carbohydrates. The extractives then contribute to the reversion mainly through their own discoloration. The transformation of the carboxyl groups in the pulp to the hydrogen form by a sulfur dioxide treatment usually increases the brightness stability in a moist atmosphere and decreases it under dry conditions. Our results also strongly indicate that the brightness reversion is highly dependent on the degree of chlorination of residual lignin.