No description available.

No description available.

No description available.

No description available.

Glycosaminoglycan-peptide complexes (GAG-P) and some proteoglycans from long bones, breast muscle, comb, crop, gizzard, heart, infundibulum, intestines, isthmus, kidney, leg muscle, liver, lung, magnum, oesophagus, ovary, pancreas, proventriculus, skin, shell gland, spleen, trachea, vagina, wattle, cecum, egg yolk and adipose tissue of the white leghorn hen were isolated and analysed for constituent units. Techniques of identification included infrared spectroscopy, cellulose acetate electrophoresis, colorimetric reactions, ion-exchange chromatography and scanning electron microscopy. The in vivo incorporation of {('14)C}-glucosamine (GlcN) and {('14)C}-galactosamine (GalN) for 1-, 2-, 120-, and 240-hour periods, and {('14)C}-glucose (Glc) and {('14)C}-galactose (Gal) for a 48-hour period into whole tissues, acetone-extracted tissues and GAG-P were investigated. Radioactivity in excreta was measured. ('14)CO(,2) from the {('14)C}-hexose treated birds was determined. In vitro incorporation of ('14)C from {('14)C}-Glc, {('14)C}-Gal, {('14)C}-GlcN, {('14)C}-GalN, {('14)C}-fructose and {('14)C}N-acetylneuraminic acid were studied.

Frc, a major gene on chromosome 8, conditions fructan levels in onions (Allium cepa L). In order to assist genetic dissection of this locus, this study aimed to determine the factors influencing varying fructan levels in high- and low-fructan genotypes. Mapping families were developed and analysed to study the genetic architecture for the fructan trait, and to check the association of the identified variables with the Frc locus. To facilitate reliable and practicable sugar assays in onions, a newly-adapted high-throughput microplate enzymatic assay was validated in this study. The reliability of using leaf sugars as a representative of bulb sugars in a mapping population was studied. Microplate enzymatic sugar assays were carried out on a segregating onion cross to validate the use of maltases in sugar analysis, and the results obtained were validated against HPLC-PAD. Sucrose measured in microplates employing maltases as the hydrolytic enzyme was in agreement with HPLC-PAD results. Maltase enzymes specifically hydrolysed sucrose in onions, providing an alternate tool in place of expensive sugar assay kits. Use of the microplate-enzymatic assay provided a rapid, cheap and practicable method for sugar analysis in onion. Differences in carbohydrate content, sucrose metabolising enzyme activities and their expression levels were monitored in developing leaf blades and leaf bases of four high- and four low-fructan genotypes. The variation in fructan accumulation between high- and low-fructan genotypes was due to the variation in sucrose metabolism. SPS expression and activity did not vary between high- and low-fructan genotypes. Acid invertase and 1-SST showed significant variation in their activities between the two fructan groups. Post-transcriptional and translational regulation of AI and 1-SST respectively, are suggested. Mapping populations analysed for non-structural carbohydrates showed very wide segregation for fructan (80 to 600 g kg⁻¹) and other NSC content, and were well-suited for detailed genetic and physiological analysis. Single marker analysis was carried out to study the association between the combined enzyme activity (CEA; acid invertase + 1-SST) and the Frc markers. Significant association between CEA and Frc markers has suggested genes regulating acid invertases or 1-SST or both underlie Frc. Leaf blade NSC did not correlate with bulb sugars and thus cannot be used as a phenotypic marker for early selection of bulb NSC traits.

No description available.

This thesis describes the synthesis of some novel carbohydrate lactones and their uses as starting materials in (a) the syntheses of various polyfunctionalised cyclopentanes, via intramolecular aldol condensations, (b) the synthesis of 1-epihydantocidin, in which the crucial synthetic step involves a novel transformation induced by tetra-n-propylammonium perruthenate, and (c) the syntheses of various tetrahydrofurans and tetrahydropyrans. The syntheses of 3,4-O-isopropylidene and cyclohexylidene altrono and allono-1,5-lactones via Kiliani ascension of protected forms of D-ribose are described. The stereochemistry of the major reaction product, which was identified as 2,3-O-isopropylidene-D-altrono-l,5-lactone was confirmed by X-ray diffraction. Introduction of azide and iodide at C-2 is achieved via silyl protection of C-6 and formation of the 2-O-triflates. Nucleophilic displacement with azide or iodide produces mixtures of C-2 epimers. Desilylation is readily achieved by treatment with acetic acid to yield azido and iodo alcohols. Attempted oxidation of C-6 to an aldehyde functionality, in an attempt to effect cyclopentane formation via intramolecular aldol condensation of C-2 onto C-6 failed. Treatment of altrono and allono azido alcohols with tetrapropylammonium perruthenate unexpectedly results in the formation of a [2.2.2.] bicyclic hemiaminal, whose structure was confirmed by X-ray diffraction. Conversion of the amine functionality to a urea is effected by treatment with potassium cyanate. Cyclisation of the urea functionality onto the lactone carbonyl and subsequent deprotection effects the synthesis of 1-epihydantocidin. Investigations into acid catalysed epimerisation of the spiro centre in both hydantocidin and 1-epihydantocidin are described. Potassium carbonate induced ring contraction of 6-O-silyl altrono- and allono- 1,5-lactone-2-O-triflates yields tetrahydrofurans, the stereochemistry of which is confirmed by conversion to symmetric materials. Intramolecular Mitsunobu cyclisation of OH-2 onto C-6 of altrono-1,5-lactones effects tetrahydropyran formation. Inversion of C-5 of the known 3,4:5,6-di-O-ispropylidene-D-glycero-D-galacto-heptono- 1,5-lactone is described. Confirmation of product stereochemistry is achieved by conversion to 2,3-O-isopropylidene-L-altrono-1,5-lactone. Introduction of iodide and azide at C-2 is achieved via the formation of the 2-O-triflate. Selective deprotection of the 5,6 isopropylidene and subsequent periodate cleavage yields aldehydo lactones which undergo potassium fluoride induced intramolecular aldol cyclisation, to yield bicyclic [2.2.1.] azido and iodo carbocycles. Sodium azide induced intramolecular aldol cyclisation of 5-azido-5-deoxy-3,4-O-isopropylidene-L-galacturono-2,6-lactone, which produces two [2.2.1.] bicyclic azido carbocycles, is described. The second azido carbocycle, which is found to be the major reaction product, readily undergoes a retro aldol reaction, resulting in the formation of a third azido carbocycle, the structure of which was confirmed by X-ray diffraction. Investigations into the equilibration of these three bicyclic [2.2.1.] azido carbocycles under the reaction conditions employed to effect their formation are described. Various ring opening reactions of the second and third materials, and their uses in the syntheses of a novel amino pentol, two novel tetrahydroxy cyclopentane spirohydantoins and two novel cyclopentane amino acids are described. The structure of the asymmetric amino acid was confirmed by X-ray diffraction. Under basic reaction conditions retro aldol equilibration is seen to compete effectively with ring opening.

The synthesis of glycoconjugates has facilitated a wide variety of techniques for the detailed study of carbohydrates and their interactions in biological systems. However, when only small amounts of the isolated oligosaccharide are available, multistep synthetic approaches are not possible. This thesis explores new synthetic methods for the preparation of glycoconjugates without protecting group manipulations. A new glycosidation method was developed which introduces N-glycopyranosylsulfonohydrazides as glycosyl donors for the protecting group-free synthesis of O-glycosides, glycosyl azides and oxazolines. The glycosyl donors were synthesized in a single chemical step by condensing p-toluenesulfonylhydrazide with the corresponding mono- and disaccharides. The N-glycopyranosylsulfonohydrazides were activated with NBS and subsequently glycosylated with the desired alcohol or transformed to the oxazoline or glycosyl azide. Recent advances in chemoselective ligation methods for the functionalization of unprotected carbohydrates have provided new routes towards complex glycoconjugates. Despite the wide use of those chemoselective methods, the properties of these linkages have not been thoroughly investigated. Characterization of a series of glycoconjugates formed by chemoselective ligation of xylose, glucose and N-acetylglucosamine with either an acyl hydrazide, a p-toluenesulfonylhydrazide or an N-methylhydroxylamine were carried out to gain further insight into the optimal conditions for the formation and the stability of these useful conjugates. Their apparent association constants (9-74 M-1) at pD 4.5, as well as rate constants for hydrolysis were determined at pH 4.0, 5.0 and 6.0. The half-lives of the conjugates varied between 1 h and 300 days. All the compounds were increasingly stable as the pH approached neutrality. Finally, selective chemical modification of a glycosaminoglycan chondroitin sulfate was attempted at the non-reducing end by utilizing the Δ4-uronic acid functional group formed upon cleavage of the glycosaminoglycan with a bacterial lyase enzyme. The captodative double bond of the unique Δ4-uronic acid functionality was unreactive towards Michael addition, even if the carboxylate was methylated. Trials towards radical addition using thiyl radicals were unsuccessful, although a synthesized model phenyl Δ4-uronic acid monosaccharide was successfully functionalized under the same conditions.

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 6 uppsatser.