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1
Thomas, Albert. "Synthetic routes to amino sugars from 2,3-unsaturated sugars /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262513409407.
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2
Hsia, Kenneth Y. "Carbocycles from sugars". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260126.
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3
Hemmings, Philippa Rachel. "Nitrogen heterocycles from sugars". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314823.
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4
Beacham, Annabel R. "Studies on higher sugars". Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:a392cc72-9ff2-43cf-a9c4-38f16df261ff.
Testo completoAbstract (sommario):
This thesis describes the synthesis of three novel seven carbon bicyclic mimics of α-L-fucose, and of two new pyrrolidine amino sugars. 2,7-Anhydro- l-deoxy-β-L-gulo-heptulopyranose and l,2,7-trideoxy-2,7-imino-β- L-gulo-heptulopyranose were both synthesised from L-gulono-l,4-lactone. The addition of one equivalent of methyllithium to the diacetonide of L-gulono-1,4- lactone gave a keto-sugar, l-deoxy-3,4;6,7-di-0-isopropylidene-β-L-gulo- heptulofuranose. The anomeric configuration of this compound was determined by equilibrium nOe measurements. Hydrolysis in aqueous trifluoroacetic acid caused simultaneous deprotection, isomerisation and dehydration to yield 2,7-anhydro-l-deoxy-β-L-guloheptulopyranose, a highly stable, rigid bicyclic system. The structure of the bicyclic system was confirmed by X-ray crystallographic studies on a crystalline derivative. The introduction of nitrogen at C-6 of L-gulono-l,4-lactone was achieved via the azide displacement of the known bromide, 6-bromo-6-deoxy-2,3-0- isopropylidene-L-gulono-l,4-lactone. Protection of the C-5 hydroxyl group as its silyl ether was followed by the addition of one equivalent of methyllithium to the carbonyl group to give a keto-sugar, 7-azido-6-(0-tert-butyldimethylsilyl-l,7- dideoxy-3,4-0-isopropylidene-β-L-gulo-heptulofuranose. Removal of the protecting groups followed by reduction of the azide functionality gave the bicyclic hemiaminal, l,2,7-trideoxy-2,7-imino-β-L-gulo-heptulopyranose, a stable but hygroscopic solid. A third bicyclic system, 2,7-anhydro-l,2,6-trideoxy-2,6-imino-β-L-gulo- heptulopyranose, was synthesised from diacetone-D-mannose via the known ketosugar, 6-azido-7-0-tert-butyldimethylsilyl-l,6-dideoxy-3,4-0-isopropylidene-β- L-gulo-heptulofuranose. Removal of the protecting groups from this keto-sugar, followed by reduction of the azide functionality, gave the target system. Analysis of the NMR spectra showed that this existed as an equilibrium mixture of the closed, bicyclic hemiaminal form and the monocyclic imine form, with the bicyclic form predominating in all solvents investigated. The sodium borohydride reduction of l-deoxy-3,4;6,7-di-0-isopropylidene-β-L-gulo-heptulofuranose gave a single product, the heptitol 7-deoxy-l,2;4,5-di-0-isopropylidene- L-glycero-D-gluco-heptitol. This was converted into two novel pyrrolidine amino sugars, l,2,5-trideoxy-2,5-imino-L-glycero-L-allo-heplitol and l,2,5-trideoxy-2,5-imino-L-allitol. The two free hydroxyl groups in the heptitol were converted into leaving groups and one was then displaced selectively with sodium azide. Reduction of the azide functionality gave an amine which cyclised onto the remaining leaving group to form the pyrrolidine framework. Complete deprotection of this product gave l,2,5-trideoxy-2,5-imino-L-glycero-L-allo- heptitol, the structure of which was confirmed by X-ray crystallographic studies on a crystalline derivative. Removal of the primary acetonide from the cyclisation product and subsequent periodate cleavage gave an aldehyde which was then reduced to an alcohol. Deprotection then gave the second pyrrolidine amino sugar l,2,5-trideoxy-2,5-imino-L-allitol. The effect of all five target compounds on eleven human liver glycosidase enzymes was investigated, and these results are also reported.
5
Pornpakakul, Surachai. "Synthesis of carba-sugars". Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683737.
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6
Elliott, Russell Phillip. "Sugars as homochiral starting agents". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316887.
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7
Hindle, Neil. "Amino sugars and their glycosides". Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:78ab400f-4a4c-47bb-9d18-1b3bef205044.
Testo completoAbstract (sommario):
This thesis describes approaches to the transformation of simple carbohydrates into a polyhydroxylated pyrrolidine and the formation of its glucosides. Chapter one describes the synthesis of the naturally occurring pyrrolidine 2,5-dideoxy-2,5-imino-D-mannitol. Synthesised from di-O-isopropylidene-D-glucose, the key steps are the introduction of nitrogen at C-5 with retention of configuration. Then cyclisation of the nitrogen onto the C-2 position with inversion to form the pyrrolidine ring. Reduction of the aldehyde furnished the polyhydroxylated heterocycle in 3.4% yield over 16 steps. The synthetic compound matched the naturally occurring compound in all respects. Chapter two contains a review of commonly used glycosylation methods. It also describes the glycosylation of di-O-isopropylidene-α-D-glucose as a model system comparing the Koenig-Knorr method to the trichloroacetimidate method using several reaction conditions. Glycosylation of 2,5-dideoxy-2,5-imino-D-mannitol was carried out using the trichloroacetimidate method to synthese all four glucosides. Boron trifluoride etherate and trimethylsilyl trifluoromethanesulphonate were used as catalysts in dichloromethane, diethyl ether and acetonitrile under strictly anhydrous conditions. All four glucosides were prepared 1-O-(αβ-D-glucopyranosyl)-2,5-dideoxy-2,5-imino-D-mannitol and 3-O-(αβ-D-glucopyranosyl)-2,5-dideoxy-2,5-imino-D-mannitol. Biological screening carried out against a wide range of glycosidases and glycosyl transferases indicated that the glucosides showed little inhibition in comparison to 2,5-dideoxy-2,5-imino-D-mannitol. Chapter three describes the isolation and identification of 1-O-(β-D-glucopyranosyl)- 2,5-dideoxy-2,5-imino-D-mannitol from Nephthytis poisonii N.E.Br. a member of the Araceae family found in tropical Africa. Identification was made by comparison with the previously synthesised glucosides of 2,5-dideoxy-2,5-imino-Dmannitol. Investigations of Hyacinthoides non-scriptus (L.) chouard ex Rothm are also discussed. Chapter four describes the synthesis of a diazidolactone that could be used to form a 1,5 disubstituted tetrazole. This would have a second nitrogen functionality in the molecule allowing the possibility of the inclusion of the tetrazole into a peptide sequence. The synthesis was carried out from L-gulono-1,4-lactone. An azido group was introduced selectively at C-2, this unexpectedly occurred with retention of configuration. A second azide was then introduced at C-5, this occurring with the more commonly observed inversion of configuration to afford the 2,5-diazido-2,5-dideoxy-D-manno-1,4-lactone.
8
Dransfield, Paul John. "New routes to imino sugars". Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247066.
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9
Goughenour, Kristie. "Histoplasma capsulatum: Drugs and Sugars". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1584377509624302.
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10
Nazeri, Gelareh. "Formation of Sugars and Organic Acids from Hydrothermal Conversion of Biomass and Biomass-Derived Sugars". Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/89694.
Testo completoAbstract (sommario):
This study provides new insights into the formation mechanisms of various organic acids from hydrothermal decomposition of biomass under non-catalytic conditions. Firstly, the primary products from hydrothermal decomposition of mallee biomass and its main components are studied. Then, systematic research is undertaken to investigate the formation of various organic acids from hydrothermal decomposition of key intermediates including cellobiose, glucose, fructose and mannose. The reaction pathways of key organic acids from various sugar compounds are revealed.
11
Ellenberger, Suzanne Ray. "Total synthesis of selected deoxyamino sugars /". Full text open access at:, 1986. http://content.ohsu.edu/u?/etd,110.
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12
Mete, A. "Novel nucleoside analogues containing modified sugars". Thesis, City University London, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355583.
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13
Li, Bin. "Innovative Methods for Biomass Sugars Utilization". University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448.
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14
Ehiwe, Tammy Iyobosa. "Investigating the bioprotective properties of sugars". Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/8076/.
Testo completoAbstract (sommario):
The purpose of this study was to investigate the stabilizing properties of osmolytes, specifically sugars on biomolecule such as protein. The strategy used in this study involved the utilisation of surfactant-rich micelles; where by the impact sugars have on the free energy of exposure of hydrocarbon groups present within the surfactant micelles was examined. The observation made for sugar-surfactant study was then applied to explain the stabilisation of the native structure and thus the physiologically active form of the protein by sugars. The sugars that have been studied include sucrose, trehalose, maltose, raffinose and mannitol. The surfactants studied were sodium decyl sulphate (SDeS), sodium dodecyl sulphate (SDS) and sodium tetradecyl sulphate (STS). Tensiometry was used to examine the impact of sugars on the critical micelle concentrations (CMC), Gibbs free energy change of micellization ( Gmic), surface pressure, surface excess concentration and area occupied per surfactant molecule. The free energy penalty of hydrocarbon chain exposure was obtained from the Gibbs free energy change of demicellization( Gdemic) which is equal but opposite in sign to the Gmic. Measurements were carried out to elucidate the influence of sugar on the aforementioned surfactant properties as a function of increasing sugar concentration. Isothermal titration calorimetry (ITC) was then used to study -sugar surfactant interactions to give enthalpy ( Hmic) and entropy ( Smic) of micellization in addition to CMC and Gmic, thus obtaining a full thermodynamic characterisation, complementing the results obtained by tensiometry. Tensiometric results revealed that at increasing concentration of sugar, the CMC of the surfactants was decreased and a more negative Gmic was obtained. ITC results revealed a similar trend for the effect of sugar on CMC and Gmic while the Hmic and Smic was increased in the presence of the sugars. The results from surfactant studies suggest an increase in the free energy penalty of hydrocarbon group exposure to the aqueous environment, due to an unfavourable interaction between the hydrophobic groups and the aqueous sugar solution. Consequently, the aggregation process is thermodynamically favoured and more spontaneous in sugar solutions. For instance in SDeS the Gmic in water and in sugar solution showed that micellization was more favourable in sugar solution ( Gmic = -19.14 kJ mol−1 at 1.0M Trehalose) than in water ( Gmic = -18.44 kJ mol−1). In addition, significant increases in surface pressure of the surfactants in the presence of sugars suggest an enhancement of the surface activity of the surfactants. Increases in area occupied per surfactant molecules in the presence of sugars suggest increase in the size of the head group area thus, possible interactions between surfactant head group – sugar or sugar-water mediated interactions. Also increases Hmic in comparison to lower values of Smic obtained by calorimetry suggest possible hydrogen bonding. In conclusion, surfactant studies suggest that sugars would stabilize biological structures by a combination of both an exclusion from the hydrophobic group due to unfavourable interactions between the hydrophobic groups and possible polar interactions between polar groups. Differential scanning calorimetry (DSC) was used to study and characterise the effect of the sugars on the thermal stability of RNase A. The results revealed an increase the thermal stability of RNase A as shown by higher Tm values in the presence of sugars. Results obtained from surfactant studies were then related to DSC results, a linear relationship between the Tm and CMC values suggests a similar mechanism. Hence, though proteins are large complex molecules, their interaction with sugars or other small solutes could be related to simple model systems such as micelles.
15
Fitzpatrick, L. M. "Transport of sugars across the chloroplast envelope". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599063.
Testo completoAbstract (sommario):
The aim of the work described in this thesis was to investigate the role and importance of the glucose transporter in the chloroplast envelope. I believed that further characterisation would contribute to our knowledge of transitory starch degradation at night, and to the control of carbon partitioning. I have supplied tracer quantities of [U-14C]glucose and [U-14C]glycerol in the dark to leaves selected from a diverse range of species, and demonstrated that the net flux in the cytosol, during starch degradation in the dark, is glycolytic, so that a gluconegoenic flux from triose-phosphates to sucrose does not occur. This provides evidence that a flucose transporter, rather than the phosphate translocator, is active in the chloroplast envelope for the synthesis of sucrose, and suggests that glucose transport across the chloroplast envelope is found throughout the plant kingdom. I have demonstrated, using the technique of silicon oil centrifugation, that chloroplasts of wild-type Arabidopsis thaliana and tobacco take up glucose but do not take up maltose from the external medium, that glucose transport in Arabidopsis is unaffected by ATP. I have also shown, by pre-labelling starch with 14CO2, that wild-type Arabidoposis chloroplasts export glucose, but not maltose, during starch degradation in the dark. These results imply that maltose is not an important final product of starch degradation in these species. I used transgenic tobacco plants, with altered levels of the triose-phosphate translocater and little impact on carbon fixation, to investigate the role of hexose transport in carbon partitioning. Careful measurements of phosphate and glucose uptake in chloroplasts of antisense and wild-type plants revealed that there was no alteration in glucose uptake, and that the endogenous wild type capacity may be sufficiently high to account for a compensatory flux in glucose transport. I hypothesised that a mutant of Arabidopsis (sex1), with chloroplasts deficient in glucose transport and accumulating starch, did so through increased starch synthesis at night. To support this, I found no differences in the maximal catalytic activities of amylases, starch phosphorylase, phosphoglucomutase, glucokinase and phosphofructokinase (ATP) in chloroplasts isolated from dark-acclimated leaves of sex1 and the wild type.
16
Tran, Chuong Hao. "Synthesis of pseudo-sugars and related compounds". Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308507.
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17
Wu, Luis Eduardo. "Synthesis of unnatural sugars from unsaturated ketones". Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368669.
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18
Young, Anne A. "Nitrile oxide/isoxazoline approach to higher sugars". Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/11655.
Testo completoAbstract (sommario):
The application of nitrile oxide/isoxazoline chemistry towards the synthesis of higher sugars (monosaccharides containing seven or more contiguous carbon atoms) has been investigated. This convergent approach, involving the cycloaddition of sugar derived alkene and nitrile oxide fragments and subsequent manipulation of the resulting isoxazoline, has much of the product stereochemistry preselected. Three ω-unsaturated monosaccharides were chosen for study: the D-glucose-derived six carbon unit (94), its C-3 epimer (102) and a seven carbon alkene, (97), prepared from D-galactose. Benzonitrile oxide was employed in preliminary studies as a model 1,3-dipole to probe the π-facial selectivity of cycloaddition to these alkenes. Cycloadditions with the carbohydrate derived nitrile oxides (117), (121) and (125) were subsequently examined. For alkenes (94) and (97) a high degree of stereoselectivity (typically ca 85:15) favouring the formation of the erythro 2-isoxazoline was obtained. This observation can be rationalised in terms of the 'inside alkoxy effect' proposed by Houk in which the allylic oxygen occupies the inside position in the transition state. D-Ribo-alkene (102) proved to be an exception; cycloaddition with ethoxycarbonylformonitrile oxide (117) occurred with negligible stereoselectivity (51:49). This result demonstrates the role played by the homoallylic oxygen in determining the stereoselectivity. Pd/C mediated reductive hydrolytic cleavage of the 2-isoxazolines unmasked the β-hydroxy ketone functionality of the deoxy-ulose derivatives. Subsequent reduction furnished a pair of separable diastereomeric 1,3-diols, whose stereochemistry was determined by examination of the ^1H n.m.r. spectra of the corresponding isopropylidene ketals. A series of deoxy -octose, -nonose, -decose, -dodecose and -tridecose monosaccharides have been thus prepared. Finally, other aspects of isoxazoline chemistry have been investigated. The reduction of isoxazoline (123) by lithium aluminium hydride afforded the syn-γ-amino alcohol (176) as the only isolated product. Trans α-enones (174) and (175) were synthesised stereospecifically by dehydration of the corresponding β-hydroxy ketones.
19
Parry, Loren L. "The synthesis of branched sugars and iminosugars". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:2a511d58-f626-4f7e-aebc-f595b147827a.
Testo completoAbstract (sommario):
Iminosugars, carbohydrate analogues in which nitrogen replaces the endocyclic oxygen, have attracted much interest due to their biological activity. Iminosugars inhibit carbohydrate-processing enzymes, thereby affecting many biological processes. Several iminosugars are licensed drugs, with many more compounds undergoing clinical trials. The main subject of this thesis is the synthesis and evaluation of novel iminosugars, particularly the effects of structural modifications on the biological activity of these compounds. Chapter 1 describes the role of carbohydrate-processing enzymes in the body, and explores the therapeutic applications of iminosugars that arise from their activity against these enzymes. Examples of substituted iminosugars are reviewed, and the effects of substituents on enzyme inhibition are described. Chapter 2 concerns methyl-branched swainsonine derivatives. Swainsonine has shown potential as a cancer treatment through its inhibition of α-mannosidase. The synthesis of (6R)- and (6S)-C-methyl D-swainsonine is described; both compounds were potent and selective α-mannosidase inhibitors (IC50 3.8 μM, 14 μM). Although less active than the parent compound, their selectivity for Golgi mannosidase over lysosomal mannosidase may be more important than the absolute value against the model enzyme. Chapter 3 describes the synthesis of a 2-C-methyl L-fucose derivative. A diastereoselective Kiliani reaction allowed the formation of a single lactone bearing a new quaternary centre. The utility of this intermediate in accessing di-branched iminosugars was explored; however, attempts to introduce nitrogen to the lactone lacked the necessary stereoselectivity. Chapter 4 relates to the synthesis of pyrrolidine iminosugars, specifically methyl amides. Two enantiomeric dihydroxyproline amides were synthesised; the D-proline derivative was a potent β-N-acetylhexosaminidase inhibitor (IC50 values of up to 3.6 μM), but the L-enantiomer was completely inactive. Inhibition of N-acetylhexosaminidases is relevant to the treatment of cancer and lysosomal storage diseases, and this work contributed to a wider project investigating the effects of altered stereochemistry on the biological activity of pyrrolidine amides.
20
Uneyama, Emi. "Synthesis of bicyclic difluorinated analogues of sugars". Thesis, University of Leicester, 2007. http://hdl.handle.net/2381/29998.
Testo completoAbstract (sommario):
This thesis describes the synthesis of gem-difluorinated cyclooctenone analogues using building block approaches based on the RCM with Grubbs' catalysts.;Des- and gem-dialkyl-substituted difluorodienes were synthesised from commercially available trifluoroethanol by dehydrofluorination/metalation, trapping, allylation and [2,3]-Wittig rearrangement successfully.;The gem-difluorinated dienes produced the corresponding difluorinated cyclooctenones smoothly and in good yields. However, a dithioketal-containing diene did not afford any cyclic product. Thorpe-lngold effect was also observed from the concentration study of des- and gem-dimethyl dienes in the RCM reaction. The gem-dimethyl diene cyclised faster than des-dimethyl diene, and the des-dimethyl diene could cyclise only at low concentration (0.001 M).;The cyclooctenone analogues have interesting topological conformations, which were studied by NMR experiments and computational calculations.;The dihydroxylation and stero-controlled epoxidation were developed on unique 8- membered ring molecules. Dihydroxylation reactions gave mixtures of diastereomeric triol products, which underwent transannular collapse to afford bicyclic products. The stereo-controlled epoxidation with methyl(trifluoromethyl) dioxirane gave the corresponding trans-epoxyalcohol in good yields. The epoxides were very stable under acid conditions however, in basic aqueous solution with microwave irradiation, they afforded bicyclic molecules by a transannular reaction via hemiaminal formation next to fluorine atoms. The newly synthesised conformationally locked difluorinated bicyclic molecules are hydrolytically resistant sugar mimics.
21
Barker, Kathrine. "Novel di-branched monosaccharides and imino sugars". Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:5e9ef70b-9213-4c0c-b500-61200a049c1b.
Testo completoAbstract (sommario):
Branched chain sugars display a varied and valuable range of biological activities. This thesis concerns the synthesis of 3,5-di-C-methyl-D-glucose, a potential inhibitor of glycogen phosphorylase (GP), and therefore a proposed therapeutic agent for type 2 diabetes. Chapter 1 looks at the occurrence of branched sugars in the natural world and current therapies for type 2 diabetes. Inhibition of GP is explored, and the molecular modelling studies which led to the design of the project target. Chapter 1 also looks into the development of new foodstuffs, the chemistry and biochemistry of imino sugars and branched hydroxy proline analogues. In Chapter 2, a range of different approaches to 3,5-di-C-methyl-D-glucose are investigated. Most of the initial investigations were carried out on the L-enantiomer, a readily available test system deriving from 2-C-methyl-D-ribono lactone. 2-C-Methyl-D-ribono lactone is synthesised rapidly from D-glucose in a one-pot reaction; as the key starting material for this work, the scalability of this process was investigated. One of the attempted syntheses of di-C-methyl glucose lead to the development of a route towards 3,5-di-C-methyl fructose, a novel dibranched ketose sugar. It was envisaged that through an enzymatic transformation, it might be possible to produce 3,5-di-C-methyl glucose stereoselectively. Synthesis of both enantiomers of 3,5-di-C-methyl glucose and mannose are reported, alongside results of GPb inhibition studies. Analysis of the preferred ring size of a range of di-C-methyl branched sugars and sugar lactones generated in this work is also presented. Chapter 3 explores the chemistry of 2,4-di-C-methyl-L-arabinono lactone, a key intermediate in the synthesis of 3,5-di-C-methyl-L-glucose. From this lactone a novel deoxy sugar, 2-deoxy-2,4-di-C-methyl-L-arabinono lactone, was generated. Routes towards a selection of imino sugars were explored, resulting in the synthesis of a methyl branched isofagomine analogue. A substituted aziridine was synthesised, from which a route to a di-C-methyl branched piperidine was proposed, and a pyrrolidine. Also presented is a synthesis of a dihydroxy di-C-methyl branched proline analogue. Detailed NMR analysis of several of the sugars generated in this work was carried out by Dr M. Wormald, of the University of Oxford Biochemistry department. The results of these investigations are presented in the Appendix. Throughout this work, the presence of quaternary centres has posed a problem with the assignment of relative configuration. As a result, this work has been greatly supported by X-ray crystallography, and the structures shown herein were wholly generated by me. Several other crystals were run during the course of this work, not all pertaining to these projects, and are provided in the CD appendix.
22
Gogar, Ravikumar Leelamchand. "Economic Production of Furans from Lignocellulosic Sugars". University of Toledo / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1595977336480846.
Testo completo
23
Kishore, P. V. "Studies on fermentation of sugars to glycerol". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Poona, 1985. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3219.
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24
Homan, Christopher David. "Phosphorus derivatives of carbohydrates". Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239564.
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25
Park, Sung-Hae. "The biosynthesis of the deoxyhexose moieties in oleandomycin /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8152.
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26
Alonzi, Dominic S. "Cellular Mechanism of Glycosylation Inhibition by Imino Sugars". Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487138.
Testo completoAbstract (sommario):
Glycosylation is the most common posttranslational modification of proteins. It is a complex process involving many functional proteins and resulting'in a great diversity of structures. The retention of glucose residues on N-linked oligosaccharides following ER a-glucosidase inhibition by imino sugars such as N-butyl deoxynojirimycin, increases the protein misfolding and the amount of glycoprotein destined for degradation via the endoplasmic reticulum associated degradation (ERAD) pathway. Intracellular peptide N-glycosidases (PNGases) act generating free oligosaccharides (FOS) and the protein is targeted for digestion. Free oligosaccharides were extracted from cells treated with NB-DNJ and subjected to ion-exchange chromatography before fluorescence labelling with 2-AA (anthranilic acid) and lectin-affinity chromatography. Separation of labelled FOS by NP-HPLC provided a rapid and sensitive method for the detection of all FOS species resulting from the degradation of glycoprotein exported from the ER. A. robust, cellular-based assay for ER a-glucosidase activity in the presence of inhibitor was developed that provided meaningful kinetics for a-glucosidase-mediated hydrolysis ofN-linked oligosaccharides as proteins are folded in the ER. Furthermore, the origin of FOS generation was studied, to determine the relative amount of FOS produced as a result of ERAD (protein derived) relative to the amount produced by a possible hydrolytic activity of oligosaccharyltransferase (lipid linked derived). A dual localisation of PNGase activity and non-proteasomal and proteasomal ERAD were demonstrated. Analysis of FOS in endomannosidase negative/non-utilised cells revealed the extent of ER/Golgi recycling of glycoproteins and the role of this enzyme in qua~ity control pathways in cells. Oral administration of NB-DNJ results in the production of glucosylated free oligosaccharide in vivo. Further to cellular based assays these glucosylated free oligosaccharides were detected in murine and human samples. The observed differences in the free oligosaccharides produced in different tissues can be explained according to hypothesises generated from culture cell studies. The effects observed with NB-DNJ, a therapeutic with considerable potential for treating lysosomal storage disorders and reducing viral infectious processes, was dose and time dependent so enabling the pharmokinetics of NB-DNJ to be observed. These studies also elucidated a transrenal method of clearance of glucosylated FOS and demonstrate that glucosylated FOS are excellent non-invasive in vivo biomarkers for a-glucosidase inhibition and protein misfolding in the ER.
27
Kérourédan, Erwan. "Concise syntheses of diflouroanalogues of cyclitols and sugars". Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/29980.
Testo completoAbstract (sommario):
The synthesis of (1 fl*,2f*,3S*,4S',)-5,5-dif luorocyclohexane-1,2,3,4-tetrol was accomplished with an overall yield of 20 % from trifluoroethanol over 8 steps featuring a key dehydrofluorination/metallation followed by trapping of aldehyde (scheme). The route based on a fluorinated building block approach delivered rapidly a small library of difluoroanalogues of carbasugars using readily available and inexpensive starting materials where the use of protecting group chemistry was reduced to its minimum as well as purification. This chemistry is unique as a method for the rapid syntheses of difluorinated molecules of this level of complexity and relevance to saccharides. Upjohn r dehydrofluorination/ R3R4c Donohoe f RCM R'v f R", F retaliation, R1 X OH OH OH Claisen The synthesis in water of a range of trifluoroethanol ethers represents an atom efficient and sustainable solution to the multigram scale syntheses of some trifluoroethyl ethers 3-(2 2',2'-Trifluoroethoxy)prop-1-ene was obtained on a mole scale with 99 % yield. Dehydrofluorination/metallation at low temperature (-100 °C) followed by trapping of aldehyde occurred efficiently with a wide variety of substrates allowing a rapid synthesis of dienols on a comfortable scale (up to 75 mmol). After Claisen rearrangement of the dienols, sodium borohydride was found to be the most diastereoselective as well as practical reducing agents tested for the reduction of the hydroketones. Ring closing metathesis using second generation Grubbs' catalyst afforded rapidly key difluorinated cyclohexenes in high yield and low catalyst loading from free diols such as (1 S*,2S*)-6,6-Difluorocyclohex-3-ene-1,2-diol which was obtained with an overall yield of 44 % from trifluoroethanol over 5 steps. The scope and limitations of Upjohn and Donohoe dihydroxylation procedures were identified for our substrates presenting an extensive variety of substitutions. Dihydroxylation under Upjohn conditions exhibited from average to excellent diastereoselectivity depending of the position and level of substitutions. Donohoe-type dihydroxylations delivered the expected outcome for each substrate in very high diastereoselectivity. Indeed (1S*,2S*,3r*,4S*,6S,,)-5>5-difluoro-2,6-dimethylcyclo hexane-1,2,3,4-tetrol was obtained as a single diastereoisomer with an overall yield of 11 % from trifluoroethanol over 8 steps. Also, the use of these intermediates as candidate for analogues of NDP sugars was investigated for a limited number of our substrates such as (1 S*,4f*>5R*,6S'*)-6- (benzyloxy-difluoro.S-dihydroxycyclohexyl dibenzyl phosphate which was synthesised with an overall yield of 27 % from trifluoroethanol over 8 steps.
28
McGowan, Sheila Anne. "Modulation of the immune response by imino sugars". Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501808.
Testo completoAbstract (sommario):
Imino sugars are carbohydrate-like alkaloids largely characterised over the last ten years that function as glycosidase inhibitors as they mimic the sugar moiety of the natural substrate. They have been reported to have immunomodulatory activity and the purpose of this study was to identify and characterise such activity. The ability of over sixty imino sugars to modify macrophage/dendritic cell cytokine production was analysed. The immunomodulatory activity of two imino sugars MNLP 462a and MNLP 24 with pro-inflammatory activity was studied in depth. They were found to upregulate in vitro macrophage IL-12 production and dendritic cell IL-12 and IL-2 production as well as co-stimulatory molecule expression particularly CD40, but in addition CD80 and CD86 on dendritic cells.
29
Kedward, Claire. "Crystallization of sugars in the chocolate crumb process". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324012.
Testo completo
30
KeÌroureÌdan, Erwan. "Concise syntheses of difluoroanalogues of cyclitols and sugars". Thesis, University of Leicester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436598.
Testo completo
31
Holt, Karen Elizabeth. "Asymmetric synthesis of aza-sugars using aldolase enzymes". Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/272658.
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32
Vázquez, Danilo Eduardo Díaz. "On AdS/CFT correspondence beyond SUGRA". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15714.
Testo completoAbstract (sommario):
Diese Arbeit beschäftigt sich mit drei Aspekten der AdS/CFT-Korrespondenz, die alle einen Schritt über die klassische SUGRA-Näherung hinausgehen. Zuerst diskutieren wir den BMN Grenzfall der Korrespondenz und untersuchen insbesondere das Verhalten der quantenfeldtheoretischen Propagatoren. Dabei weisen wir nach, dass die Propagatoren im für den BMN Fall relevanten Hintergrund ebener Wellen semiklassisch (WKB) exakt beschrieben werden. Danach wird im Rahmen der AdS/CFT-Korrespondenz der Grenzfall verschwindender Kopplung der konformen Feldtheorie betrachtet. Zur technischen Vereinfachung geschieht dies für das Beispiel des O(N)-Vektormodells. Dabei wird die OPE der Vierpunktfunktionen so umgeschrieben, dass sie strukturelle Ähnlichkeit mit Witten-Diagrammen einer korrespondierenden Theorie von Strömen mit höherem Spin hat. Außerdem wird das O(N)- Vektormodell bei großem N am wechselwirkenden Infrarot-Fixpunkt untersucht. Im letzten Punkt wenden wir uns schließlich der ursprünglichen AdS/CFTDualität unter Mitnahme der nächstführenden Ordnung der 1/N-Entwicklung zu. Für die Deformationen der CFT durch relevante Doppelspur-Operatoren finden wir bei Zustandssummen und konformen Anomalien exakte Übereinstimmung zwischen direkter und AdS-seitiger indirekter Rechnung. Damit wird ein nicht trivialer Test der Korrespondenz über die SUGRA-Näherung hinaus erbracht.This thesis deals with three corners of the AdS/CFT Correspondence that lie one step beyond the classical supergravity (SUGRA) approximation. We first explore the BMN limit of the duality and study, in particular, the behavior of field theoretic propagators in the corresponding Penrose limit. We unravel the semiclassical (WKB-) exactness of the propagators in the resulting plane wave background metric. Then, we address the limit of vanishing coupling of the conformal field theory (CFT) at large N. In the simplified scenario of Higher Spin/O(N) Vector Model duality, the conformal partial wave (CPW) expansion of scalar four-point functions are reorganized to make them suggestive of a bulk interpretation in term of a consistent truncated massless higher spin theory and their corresponding exchange Witten graphs. We also explore the connection to the interacting O(N) Vector Model at its infra-red fixed point, at leading large N. Finally, coming back to the gauge theory, we study the effect of a relevant double-trace deformations of the boundary CFT on the partition function and its dual bulk interpretation. We show how the one-loop computation in the Anti-de Sitter (AdS) space correctly reproduces the partition function and conformal anomaly of the boundary theory. In all, we get a clean test of the duality beyond the classical SUGRA approximation in the AdS bulk and at the corresponding next-to-leading 1/N order of the CFT at the conformal boundary.
33
Wan, Chun Hong. "Sugars and polyol compounds in ambient aerosols and cooking fume aerosols /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202006%20WAN.
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34
Yi, Wang. "Sugar control of artemisinin production". Worcester, Mass. : Worcester Polytechnic Institute, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-042906-210543/.
Testo completo
35
Duff, Fraser John. "Synthesis of aza-C-disaccharides using a functionalised cyclic nitrone". Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/581.
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36
Walford, Caroline L. "An approach to the synthesis of C-glycosides using nucleophilic glycosyl donors". Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285371.
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37
Waltho, Jonathan Peter. "Structural studies on bio-active molecules". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236091.
Testo completoAbstract (sommario):
This thesis deals with the structure determination of some natural products in the molecular weight range 700 - 2000 daltons, using a combination of FAB mass spectrometry and proton NMR spectroscopy. Furthermore, the defined structural details have been used to investigate the driving forces behind molecular conformation and intermolecular interaction. The first section involves the structure elucidation of the saccharide portions of four glycosides isolated from a wild plant of potent pharmacological activity. The positive and negative ion FAS MS fragmentation pattern of six glycosides of known structure was investigated in order to ascertain the predictive power of the technique for unknown compounds of this class. With the saccharide sequence information determined using FAB MS studies, high resolution two-dimensional proton NMR spectroscopy was employed to identify the individual monosaccharide units and their order of linkage. In two cases, it was necessary to determine the spatial proximity of protons using spin-locking NMR techniques. In the second section, similar techniques were applied in the structure elucidation of a complex of glycopeptide antibiotics of the vancomycin family. The final structural details, identification of the fatty acyl groups, were resolved using chemical degradation/GCMS methods. In the third section, NMR experiments have been used to investigate the intramolecular determinants of conformation within the mobile regions of vancomycin. This includes exchange and rotational phenomena, and changes in molecular motion as the charge of the antibiotic is varied. The effects of the two protonated amino groups of vancomycin on the binding of models of bacterial cell wall peptides was examined. The amino groups are orientated such that they retain optimum exposure to the solvent whilst interacting with the bound peptide in two ways: via direct electrostatic interaction and via perturbation of the solvent, thus modifying the energetics of hydrophobic interactions. The conformational changes of ristocetin (in aqueous acetonitrile solution) on binding of model peptides were investigated. In addition, it was observed that ristocetin-peptide complexes dimerise at millimolar concentrations, and the geometry of the dimer was determined. The interactions that stabilise the dimer are remarkably similar to those that stabilise the peptide complex itself. Finally, possible roles for the sugars mannose and ristosamine in ristocetin, and vancosamine in canvomycin are discussed, with particular emphasis on the selectivity that they impose on the binding site of these antibiotics.
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Milton, Mark John. "Multidimensional and heteronuclear NMR investigations of oligosaccharides in the free and protein bound states". Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/14184.
Testo completoAbstract (sommario):
The three dimensional structure and dynamics of three biologically important oligosaccharides were probed using a range of NMR techniques. The solution structure of oligosaccharide moiety of was solved using conventional 1H - 1H ROESY data in conjunction with molecular dynamics simulations. It was evident from this study that the dominant conformation in free solution is similar to the structure of oligo-GM1 in complex with the B-subunit of the enteropathogenic cholera toxin. The solution dynamics of an analogue of globoside (Gb4-OEtTMS), a cellular receptor for an E. coli verotoxin, was also elucidated using conventional 1H - 1H ROESY data. However, it was not clear that these data alone could adequately model the structure. Additional distance restraints were derived from 1H - 1H NOE contacts between exchangeable and non-exchangeable protons measured in H2O/acetone-d6 solutions at low temperature (-15 °C). It was concluded on the basis of these studies that Gb4-OEtTMS is an extremely flexible sugar, however, the time- averaged conformation was similar to the proposed conformation of Gb4 in complex with a verotoxin (VT2e). In order to increase the structural information which may be measured from NMR spectroscopy, carbon-13 enriched carbohydrate moieties, commonly found in glycolipids and glycoproteins, were synthesised. Isotopically labelled N-acetyl neuraminic acid, a2,3 sialyl N-acetyl lactosamine (required for the synthesis of sialyl Lewis antigen) and a2,3 sialyl lactose (oligo-GM3), the core ganglioside which is required for the synthesis of more complex gangliosides (e.g. GM1), was accomplished using a mixture of enzymatic and synthetic methods. To test the applicability of heteronuclear NMR spectroscopy in the study of oligosaccharides, the solution structure and dynamics of [U-13C] oligo- GM3 was probed by recording three dimensional 13C-edited ROESY spectra, and long-range carbon-carbon and carbon-proton spin-coupling constants. Inter-residue ROEs could be unambiguously assigned from the 3D experiment, and these assignments contradict previous inter-residue ROE contacts published in the literature (based only on homonuclear data). Two additional inter-residue ROE contacts could be measured across the Gaibeta1-4Glc linkage. The solution conformation of [U-13C] oligo-GM3 in complex with wheat germ agglutinin was solved on the basis of 3D TRNOESY-HSQC data. Theoretical TRNOE intensities back-calculated from full relaxation matrix calculations performed on the X-ray crystal structures of the complex were consistent with experimentally measured values and confirmed the flexible nature of the Galbeta1-4Glc linkage when bound to the protein. Finally, carbon-13 enriched N-acetyl neuraminic acid and galactose were introduced into the glycan chains of an intact glycoprotein FcREA. 13C-1H HSQC data suggest that the two arms of the biantennary glycan experience two distinct magnetic environments.
39
Bierenstiel, Matthias. "Transition Metal Catalyzed Selective Oxidation of Sugars and Polyols". Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-37863.
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40
Schneider, L. (Laura). "Mechanocatalytic pretreatment of lignocellulosic barley straw to reducing sugars". Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526216478.
Testo completoAbstract (sommario):
Abstract Biomass conversion methods represent bioeconomic solutions for the sustainable production of value added commodities (chemicals and materials) as well as for energy purposes, either in solid (pellets), liquid (transport fuels) or gaseous (combustion gases e.g. biomethane) form. Lignocellulosic biomass as a renewable source available in immense quantity, is considered to be one of the most promising natural sources, with high potential in the replacement of conventional transportation fuels and reduction of greenhouse gas emissions. This thesis provides new insights into mechanocatalysis, which as yet is a novel technique in catalytic biomass conversion. The mechanocatalytic approach combines chemical catalysis and mechanical assisted processing driven by ball milling. Lignocellulosic barley straw was impregnated or merely mixed with the catalyst (formic acid, acetic acid, sulfuric acid, oxalic acid dihydrate and potassium pyrosulfate) and ball milled under various conditions yielding the selective depolymerization of lignocellulose into water-soluble xylo-oligosaccharides. Subsequent hydrolysis at moderate temperatures resulted in the formation of valuable reducing sugars, mainly xylose, galactose, arabinose and glucose, which constitute the basic materials for transportation fuel and chemical production. Reducing sugar release of 53.4 wt% with low by-product formation was observed within short milling durations using sulfuric acid as a catalyst in mechanocatalysis. Likewise, oxalic acid dihydrate and potassium pyrosulfate as a novel catalyst, successfully converted barley straw to reducing sugars (42.4 wt% and 39.7 wt%, respectively), however longer milling durations were required. In comparison, lower saccharification (<10 wt%) was obtained by employing formic acid and acetic acid in mechanocatalysis. Harsh milling conditions initiated a temperature increase within the reaction vessel resulting in enhanced sugar release. Likewise, greater sugar release was observed with increased catalyst amount and acidity. The results revealed that the balance of these factors is crucial for efficient catalytic conversion of barley strawTiivistelmä Biomassan konvertointimenetelmät mahdollistavat biotalouden hengen mukaisesti uusia ratkaisuja kemikaalien ja materiaalien kestävään tuotantoon sekä biomassan energiakäyttöön eri muodoissa (kuten pelletit, biopolttoaineet ja biokaasu). Lignoselluloosapohjaista, uusiutuvaa biomassaa, kuten tässä työssä tutkittua ohran olkea, on runsaasti saatavilla. Lignoselluloosa onkin yksi lupaavimmista raaka-aineista korvaamaan fossiilisia polttoaineita ja vähentämään kasvihuonekaasupäästöjä. Väitöskirjatutkimus antaa uutta tietoa ohran oljen mekaanis–katalyyttisestä käsittelystä, mikä on suhteellisen uusi menetelmä biomassan katalyyttisessä muokkauksessa. Menetelmässä yhdistetään kemiallinen katalyysi ja mekaaninen muokkaus (jauhatus) kuulamyllyllä. Lignoselluloosa (ohran olki) impregnoitiin tai sekoitettiin tutkitun katalyytin (muurahaishappo, etikkahappo, rikkihappo, oksaalihappodihydraatti, kaliumpyrosulfaatti) kanssa ja käsiteltiin erilaisissa mekaanis–katalyyttisissä olosuhteissa. Lignoselluloosan selektiivinen depolymerointi muodosti vesiliukoisia oligosakkarideja ja edelleen hydrolyysin kautta pelkistyneitä sokereita (pääasiassa ksyloosia, galaktoosia, arabinoosia ja glukoosia), joita voidaan käyttää biopolttoaineiden ja -kemikaalien valmistuksessa. Tutkimuksen tulosten perusteella rikkihappokatalyytillä saatiin 53,4 massa-% ohran oljen sisältämistä pelkistyneistä sokereista vapautettua lyhyillä käsittelyajoilla. Lisäksi sivutuotteiden muodostuminen oli vähäistä. Vastaavasti oksaalihappodihydraatti (sokerisaanto 42,4 massa-%) ja kaliumpyrosulfaatti (sokerisaanto 39,7 massa-%) toimivat uusina katalyytteinä hyvin, mutta vaativat rikkihappokatalyyttiä pidemmät jauhatusajat. Sen sijaan muurahaishapolla ja etikkahapolla sokerisaanto oli erittäin alhainen (alle 10 massa-%) mekaanis–katalyyttisessä käsittelyssä. Tutkimuksessa todettiin, että voimakas jauhatus vaikutti selkeästi reaktiolämpötilan nousuun käsittelyn aikana, mikä edisti korkeampaa sokerisaantoa. Vastaavasti sokerisaantoa voitiin parantaa katalyyttimäärällä ja happamuudella. Tulokset osoittavat, että näiden muuttujien tasapaino on ratkaisevaa ohran oljen tehokkaan katalyyttisen muuntamisen kannalta
41
Mellor, Howard R. "The biological properties of novel N-alkylated imino sugars". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398134.
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42
Geary, Peter Michael. "The co-crystallisation of sugars by the supersaturation process". Thesis, University of Hull, 2008. http://hydra.hull.ac.uk/resources/hull:2576.
Testo completoAbstract (sommario):
Co-crystallising sugars by the supersaturation process was investigated using sucrose and lactose as the matrix sugars. The components to be cocrystallised with either sucrose or lactose were a variety of mono- and disaccharides along with sweeteners such as saccharin. Analysis of the materials yielded from the supersaturation process was done primarily by differential scanning Calorimetry (DSC) and powder x-ray diffraction (PXRD). DSC analysis allowed information to be obtained on the thermal behaviour of the various co-crystalline materials, whilst PXRD permitted information on the structural aspects of the materials to be gained. These two forms of analysis were complimentary to each other, each revealed unique characteristics of the co-crystalline materials. To unambiguously differentiate the difference between a material that is co-crystalline and one that is not, physical blends of the sugars to be cocrystallised were analysed by DSC and PXRD. This approach allowed for identification of all the components in the mixture, more importantly, this identification was achievable at all levels of the second component in the mixture. Co-crystallising either sucrose or lactose, with various sugars, yielded solely co-crystalline material up to a certain level of the added sugar. Once this level has been reached, two distinct phases appear in both DSC and PXRD analysis. A co-crystallised and a phase relating to the added sugar can be observed. The formation of a potentially co-crystalline material appears to result from a direct inclusion of the added sugar into the matrix sugar. DSC analysis of the co-crystallised material revealed thermal behaviour that is suggestive of a doping of the matrix sugar by the added component. PXRD analysis did provide some data to further this argument, axis elongation for co-crystallised material is suggestive of a sopping of the main phase. However, determination of the unit cell volumes did not yield conclusive evidence to help prove this hypothesis though. This behaviour in both forms of analysis was generally proportional to the quantity of the second component that has become included into the matrix sugar. The formation of solely co-crystalline materials appears to rely on the structural similarity between the matrix sugar and the component to be included. A higher degree of similarity is reflected by a high level of inclusion of the added component. Co-crystallisation appears to rely on a degree of intermolecular sugar-sugar recognition. The inclusion of a second component is not solely down to structural similarities between materials however. It appears that there are kinetic factors potentially involved to. Varying the method of co-crystallisation allowed for higher, or lower, amounts of various second components to be included within a matrix sugar. The appearance of co-crystalline materials may be due to the inclusion of the second component in an amorphous state. Analysis by Autosorb of various co-crystalline materials has dispelled this idea. All co-crystalline materials behaved in a manner that was indicative of a crystalline material. During the course of the work with sucrose, it was noted that a unique melting point was observed. From previous work, this unique phase was thought to be a hydrated form of sucrose. Further analysis on this material has allowed for further postulation on its formation and on new methods of its synthesis.
43
Liu, Wei-Chun. "Studies of enzymes that process and use charged sugars". Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547468.
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44
Neuss, Judi. "Fragmentation-cyclisation approaches to the synthesis of aza-sugars". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338541.
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45
Flack, Stephen Sean. "Studies towards synthetic receptors for small peptides and sugars". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261284.
Testo completo
46
Ahmed, Nadia Noreen. "Diels-Alder approach to the synthesis of carba-sugars". Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419540.
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47
Maciej, Marissa Lucy. "Azido sugars for the modification of glycosaminoglycans in biology". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/azido-sugars-for-the-modification-of-glycosaminoglycans-in-biology(cf34d9aa-d20b-4225-b871-93a5983832b6).html.
Testo completoAbstract (sommario):
Heparan sulphate (HS) is critical for embryonic development with involvement in a myriad of biological processes, centrally mediating morphogenic movements and facilitating the specification and differentiation of tissues. Complicated by its structural micro-heterogeneity along with expression on numerous different proteoglycan cores, the plethora of roles for HS in biology and their underlying mechanisms have not yet been fully defined. The discovery and characterisation of new reagents and methods for modification of HS expression and/or structure will aid efforts in elucidating the structure and activity of this glycosaminoglycan. Until now, azido sugars have been utilised as labelling reagents for various types of glycosylation, including N-glycans, O-linked mucin-type glycosylation and O-GlcNAcetylation of proteins. Incorporation of the unnatural azido sugar into the glycan of interest inserts a chemically reactive abiotic azide for subsequent detection via Staudinger ligation or click chemistries. However, to our knowledge, application of these azido sugars has not been explored for glycosaminoglycans. A metabolic labelling approach using Ac4GalNAz yields UDP-GalNAz and UDP-GlcNAz (Boyce et al., 2011), ready to target CS/DS and HS, respectively. We hypothesised that HS synthesis might be altered in the presence of UDP-GlcNAz due to the location of the azide on the acetyl group and the potential for interference with endogenous N-deacetylase-N-sulphotransferase biosynthetic enzyme activity. In mammalian cell culture (Chinese hamster ovary cells), treatment with Ac4GalNAz led to a decrease in total HS abundance accompanied by significant increases in 6-O-sulphation within the chains. Incorporation of a radiolabelled metabolic precursor revealed that average HS chain length was decreased in azido sugar-treated CHO cells. The modifications to HS were dose-dependent and HS inhibition was transient. Following removal of Ac4GalNAz from cell culture, HS expression returned to baseline levels within 24 hours. Previous work from the Bertozzi group has demonstrated the utility of Ac4GalNAz for visualising GalNAc- and O-GlcNAc-modified proteins in vivo. Using Xenopus, we were able to show that treatment of fertilised eggs with Ac4GalNAz decreased the abundance of HS in a similar way to that seen in vitro, with an associated impact on embryonic development. Embryonic axial elongation was impaired, with defective myotomal development and aberrant axonal patterning along the trunk and tail. Posterior somite cell nuclei were disorganised, with loss of distinct chevron patterning and skeletal muscle development was impaired with muscle fibres spanning some of the somite boundaries. Removal of the inhibitor partially rescued tail extension defects, as well as muscle development, but not axonal patterning. Therefore, these experiments illustrate a novel application for Ac4GalNAz as a soluble and reversible inhibitor of HS synthesis for in vitro and in vivo studies. The observed potential for control of inhibition via time- and dose-dependent effects enables targeted and selective inhibition of HS and potentially provides a powerful new inhibitor for the study of HS-mediated events.
48
Yan, Wei. "Gas phase conversion of sugars to valuable C3 chemicals". Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5504.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 31, 2009) Includes bibliographical references.
49
Buley, Taylor. "Solution conformational entropy of aldohexose sugars by Taylor Buley". Tallahassee, Fla. : Florida State University, 2009. http://purl.fcla.edu/fsu/lib/digcoll/undergraduate/honors-theses/244578.
Testo completoAbstract (sommario):
Thesis (Honors paper)--Florida State University, 2009.Advisor: Dr. André Striegel, Florida State University, College of Arts and Sciences, Dept. of Biochemistry. Includes bibliographical references.
50
Henneberry, T. J., D. L. Hendrix, H. H. Perkins, Jech L. Forlow e R. A. Burke. "Silverleaf Whitefly: Honeydew Sugars and Relationship to Sticky Cotton". College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/210320.
Testo completoAbstract (sommario):
In cotton plots heavily infested with silverleaf whitefly (SLW), Bemisia argentifolii Bellows and Perring, amounts (mg /g of lint) of sugar (fructose, glucose and sucrose combination) on lint from tagged bolls, varied but showed a general trend to increasing amounts with increasing time of exposure (days) for 52 days. Minicard lint stickiness ratings responded in a similar manner and all values were above acceptable thresholds. Lint from harvested mature open bolls that were exposed on trays suspended in the interior of SLW infested cotton plots showed increasing amounts of sugar and higher minicard ratings after 6 days. Amounts of sugar and minicard ratings were drastically reduced following rains of 1.5 inches.