The structures of the extracellular polysaccharides elaborated by Streptococcus mutans 03-5 and S. mutans OMZ 51 were investigated. These were fractionated into soluble fractions (GS-5B and OMZ 51B polysaccharides) and lesser-soluble fractions (GS-5A and OMZ 51A polysaccharides). GS-5B polysaccharide was essentially an a linked polyglucan in which 17% of the glucose units were linked through positions 1, 3 and 6 and formed branch points. 60% of the molecule comprised a single -linked glucose chain and the minimum average external chain length was 2. The polysaccharide was poly-dispersed M - 49)000 with a structurally similar low molecularweight fraction = 10,000. The following average repeating unit was proposed. GS-5A polysaccharide contained approximately 35% fructose and 40% of glucose. The polyglucan was linked through positions 1,3 and 6 and formed branch points. Approximately 3% of the glucose units were linked, through positions 1 and 3 only. An average repeating unit was proposed.

The oximes of D-arabinose, D-galactose, B-mannose and D-ribose have been synthesised and their structures determined in the solid state and in solution by a variety of chemical and physical methods. These carbohydrate oxirnes can exist in the acyclic anti(z) or syn(E) form in the solid state, and isomerise to a mixture of anti(Z, 20%) and syn(E, 80%) forms in aqueous solution. B-glucose oxime exists in the cyclic beta-pyranose form in the solid state and equilibrates to a mixture of beta-pyranose (23%), beta-pyranose (7%), syn(E, 56.5%) and anti(Z, 13.5%) forms in solution. The interconversion of carbohydrate oximes in aqueous solution was studied and found to be simple (first order) except for B-glucose oxime which showed complex isomerisation kinetics. The simple (first order) isomerisation of B-arabinose oxime was shown to be subject to specific and general acid, and specific base catalysis. B-Arabinose oxime has been shown to act as a substrate of yeast hexokinase, the product B-arabinose oxime-5-phosphate (lithium salt) has been isolated and characterised. This result together with observations of the interaction of other carbohydrate derivatives has allowed the current picture of the substrate specificity of this enzyme to be extended. By application of transition state theory carbohydrate oximes are predicted to act as inhibitors of enzymes which catalyse the interconversion of aldoses and ketoses. This prediction has been confirmed in the case of B-:xylose (B-glucose) isomerase (Streptomyces species), of which B-arabinose and B-glucose oximes are more powerful inhibitors than other compounds previously examined.

In modern society people are concerned about their state of health and if they do unfortunately become ill they want the best possible treatment to be made available to them. In order to satisfy these demands new treatments have to be developed. This can be a long and expensive process. Before any new treatment can come to market it has to be proved to be both clinically effective and economically cost-effective. With limited health care resources the cost-effectiveness of treatments is becoming ever more relevant. In order to show whether a treatment is clinically effective a clinical trial is carried out and this is now usually accompanied by an economic evaluation, so that the cost effectiveness of the treatment can be assessed. When a clinical trial aimed at preventing clinical events is analysed, a time-to-first event analysis is often performed together with a cost-effectiveness analysis. These analyses do not always make the best use of the large amounts of patient information recorded during the clinical trial. Using the randomised controlled trial (RCT) the Impact Of Nicorandil in Angina (IONA) as an exemplar, ways in which the clinical and economic evaluations of clinical trials can be expanded are explored. There are three main parts of this thesis. Firstly, following a more detailed introduction in Chapter 1, in Chapters 2 and 3 the IONA Study is introduced and the main clinical results of the study are given. Secondly, in Chapters 4, 5 and 6 the fact that patients could suffer more than one clinical endpoint is considered. The models that can be used to incorporate the recurrent events are introduced and then applied to the data from the IONA Study. Following on from this, through the simulation of recurrent event data, the performance of the models under different known conditions is assessed. Thirdly, in Chapters 7 and 8 an introduction to health economics is given and following this the main results of the economic evaluation of the IONA Study are presented. Areas in which the results of the economic evaluation can be expanded are then investigated. Finally, in Chapter 9 there is a discussion of the work as a whole and areas where there would be the possibility of further work.

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.

It was proposed that a phase separated system might be utilised to deliver a concentrated polysaccharide mucosal protective coating in gastro oesophageal reflux disease (GORD). In this context the phase behaviour of xanthan gum in combination with sodium alginate and other polymers was studied. Above a threshold concentration of alginate, aqueous mixtures of xanthan exhibited phase separation, resulting in loss of normal viscoelastic properties and the formation of a low viscosity system. The shape of the phase diagram showed behaviour typical of a segregative system, with the continuous phase composed exclusively of alginate and the disperse phase being rich in xanthan gum. Increasing alginate molecular weight reduced the threshold concentration for separation, as predicted by the Flory-Huggins theory, but changes in alginate mannuronate:guluronate ratio had no effect. Increasing ionic strength elevated the threshold concentration. Xanthan separation was elicited by other aqueous anionic polyelectrolytes, but not neutral water soluble polymers. Scleroglucan, another rigid-rod polysaccharide, was investigated as an alternative to xanthan but did not show similar separation behaviour, suggesting that the charge on the xanthan molecule is a necessary prerequisite. Reversal of phase separation by dilution across the phase boundary provided increases in viscosity. A 1% xanthan:2% alginate mixture doubled in viscosity whereas if diluted with simulated gastric fluid a seven-fold increase was seen, as a result of conversion to an alginic acid gel. This offers a mechanism for producing the desired viscosity barrier. Low viscosity polyelectrolytes, with concentrations close to the phase boundary yielded the greatest viscosity increases. In the phase separated system, the disperse phase exhibited an unusual strand-like morphology whose birefringence suggests a liquid crystalline structure. The variable size of the strands was explained in terms of kinetics of xanthan molecular aggregation in media of different viscosity.

No description available.

The incorporation of polyfluorinated regions into carbohydrates has been proposed as a strategy to improve the typically low protein–carbohydrate affinity. The creation of a hydrophobic region, while maintaining a potential for attractive dipolar interactions (mediated by the polarised C–F bond) may increase binding affinity. This thesis describes the synthesis of previously reported 2,3-dideoxy-2,2,3,3-tetrafluorogalactopyranose and 2,3-dideoxytetrafluoroglucopyranose. Further optimisations have been carried out to provide highly efficient and enantioselective routes to both compounds. The synthesis of the novel 2,3-dideoxy-2,2,3,3-tetrafluorogalactofuranose via a modification to the pyranose route has been successfully achieved and optimised. The large scale synthesis of these compounds has enabled their further derivatisation. This has included the development of phosphorylation methodology for 2,2,3,3-tetrafluorogalactose in both pyranose and furanose isomers. The synthesis of the first disaccharides to contain a tetrafluoroethylene moiety has been accomplished, providing tetrafluorinated analogues of known bioactive disaccharides. Studies have also been carried out towards different glycosylation methodologies of 2,2,3,3-tetrafluorinated sugars, enabling access to glycosylation by both electrophilic and nucleophilic reagents. Detailed conformational analysis has been implemented, with the results displaying high similarities between 2,2,3,3-tetrafluorogalactopyranosides and natural non-fluorinated carbohydrates.

This study investigated the thermal decomposition of two structurally similar polysaccharides – cellulose and alginic acid, arguably being the two largest sources of biomass on land and from the sea respectively. Despite the similarity in the two materials and applications, reviewing literature of the combustion and pyrolysis mechanisms of the two materials showed a relatively well-established framework of knowledge for cellulose, although there is still some lack of agreement in some areas. This contrasted with the almost total absence of any information on the thermal behaviour of alginic acid. The aim of the work reported in this thesis was to use the structural similarities and the mechanistic framework for cellulose to conduct a comparative investigation of the two materials. Taking advantage of high throughput multivariate algorithms to process complex spectroscopic data produced by TGA-FTIR, a method was developed to identify infrared active volatile species generated above a detectable threshold during the thermal degradation process. The ability to plot an evolution profile of a selected compound in time- and/or temperature domain significantly enhanced the capabilities of a standard TGA-FTIR system for mechanistic investigations. With the technique established, the two materials were analysed under different heating rates (5, 10, 30, 60°C/min) under nitrogen and again under 10% oxygen in nitrogen. A reconstruction of the cellulose decomposition pathway was carried out using the data obtained from this work. Compared to the methods available in the scientific literature, the current method was a simpler and more efficient technique for providing information related to the thermal degradation behaviours of the sample materials. The application of the method to alginic acid revealed for the first time that this material responded differently and more sensitively to the presence of oxygen than did cellulose. Its decomposition pathway has a number of distinctive steps, in contrast to cellulose.

The efficiency of an intermolecular synthetic transformation can be improved by temporarily linking reaction components together. The addition of a tether leads to enhanced regio- and stereocontrol by restraining the mobility of the reacting partners, effectively transforming an intermolecular reaction into its intramolecular counterpart. Silicon tethers are associated with an expanding range of applications, including hydrosilylations, cycloadditions and radical reactions. This project has continued work pioneered by the Robertson group into silicon tethered Type I ene cyclisations, extending the methodology to incorporate O-linked ene precursors with the intention of applying this chemistry to the stereoselective synthesis of non-natural carbohydrates. This investigation encompassed advances in the area made concurrently within the Robertson group and extended the scope of the ene protocol by successfully incorporating latent functionality into the R-group side chain. In addition, a new route to the O-linked ene precursors was established employing silylcyanohydrin chemistry. In general, the ene reactions proceeded stereoselectively to generate the expected oxasilacyclohexanols, which could be cleaved oxidatively to afford 1,2,4-triols. The formation of the major diastereomer was consistent with ene cyclisation proceeding through a trans-decalin type transition state (e.g. leading to compound 1). During our attempts to effect ene cyclisation in the O-linked prenyl systems we observed an unexpected side reaction, resulting from intramolecular allylic transfer. Further studies revealed that this novel process could be initiated thermally to generate 1,2-homoallylic diols with excellent levels of stereoselectivity. Tethered E- and Z-crotylsilanes were found to be equally receptive to this process. Although attempts to apply the silicon tethered allyl transfer chemistry to aldimines and glycosides failed, an extension of the methodology to incorporate cyclohexadienylsilanes was successful and provided interesting synthetic intermediates for elaboration to carbasugars.

In this project, the structures of exopolysaccharides (EPS) produced by bacterial strains were characterised. The current techniques utilised for structural elucidation were also investigated. The structure of the novel EPS isolated from the fermentation of the lactic acid bacteria(LAB) strain, Lactobacillus helveticus Rosyjski, has been characterised. The strain of LAB was grown on skimmed milk supplemented with glucose; the subsequent EPS produced was isolated using established protocols. The 1H NMR spectrum identified the presence of five anomeric monosaccharide signals corresponding to the existence of a pentasaccharide repeating unit oligosaccharide. HP-SEC-MALLS analysis revealed the EPS has a weight average molecular weight of less than 1.4 x106 g mol-1. A combination of GC-MS and HPAEC-PAD analysis confirmed that the structure was composed of D-glucose, D-galactose and D-N-acetyl mannosamine in a molar ratio of 2:2:1. Linkage analysis of the EPS, by GCMS and 2D-NMR experiments showed that the repeating unit contains two terminal, one dilinked and two tri-linked monosaccharides. All of the data obtained allowed for the elucidation of the structure of the EPS produced by Lactobacillus helveticus Rosyjski. The current techniques used for the determination of the monomers and linkages present in EPS structures were investigated. Monomer analysis was studied by using the previously characterised EPS, Lactobacillus acidophilus 5e2 as a model. A variety of acids were used to catalyse the hydrolysis of the polysaccharide. The monosaccharides liberated from the EPS were analysed by HPAEC-PAD. It was determined that hydrolysis with TFA was the simplest technique to employ whilst also providing reliable results. Linkage analysis was investigated by the production of a number of disaccharide-derived model linkage standard compounds. This resulted in the creation of a number of terminally and di-linked linkage standards which can be used as model reference compounds when characterising previously unidentified EPS. The bacterial strain Bifidobacterium animalis subsp. lactis A1dOxR produces EPS. Initial inspection of the 1H NMR spectrum however displayed a complex anomeric region with many overlapping signals. Analysis by HP-SEC-MALLS revealed multiple peaks, further adding to the evidence of the presence of more than one EPS in the recovered ‘crude’ sample. The crude sample was subjected to dialysis and a fraction (over 100,000 Da) was recovered and denoted as high molecular weight (HMW) EPS. Examination of the 1H NMR spectrum from HMW EPS indicated a hexasaccharide repeating unit oligosaccharide, whilst HPEAC-PAD and GC-MS analysis confirmed that the structure was composed of Lrhamnose, D-galactose and D-glucose in a molar ratio of 3:2:1. Further analysis determined that one of the galactose monosaccharides was present in the furanose form as appose to the more commonly observed pyranose configuration. Linkage analysis of the EPS, by GCMS and 2D-NMR experiments, showed that the repeating unit contains one terminal, four dilinked and one tri-linked monosaccharide. All of the data obtained allowed for the elucidation of the structure of the HMW EPS from by Bifidobacterium animalis subsp. lactis A1dOxR. Solubilising EPSs has been a constant challenge, however, it was hoped with the advent of ionic liquids (IL) this issue could be solved. Ultimately, dissolution of EPS in ionic liquids though proved to be unsuccessful, so attention was turned to combining derivatisation and dissolution, as a method for solubilising polysaccharides. Derivatisation of a number of model systems of di- and polysaccharides were explored. By studying both 1D- and 2D-NMR coupled with GC-MS analysis it has demonstrated that polysaccharides such as cellulose along with a number of common disaccharides can be successfully dissolved and modified in ionic liquids.