Blood group glycolipids are important tools in the study of microbial receptor interactions and other biological phenomena. Presently blood group glycolipids of interest are isolated from biological samples. However, all glycolipids are not readily available due to the low frequency of some phenotypes in the general population. The ability to acquire the rare glycolipids from the degradation of common glycolipids would be a useful alternative to trying to obtain the molecules from biological sources.This research set out to establish the ability of blood group glycolipids to be degraded into useful glycolipids in a controlled manner by acid hydrolysis and possibly metal catalysis. The initial experiments investigated the degradation/hydrolysis of the more readily available glycolipid globoside with a range of salts and acids to establish degradation concepts such as; temperature, type of acid, acid concentration, and the role of metal ions in glycolipid degradation. These concepts then led to a series of degradation experiments with the blood group glycolipids Leb and ALeb. These glycolipids were incubated with a range of acid concentrations and varying temperatures. Thin layer chromatography separation and chemical and immunochemical staining were the main methods used to identify the products of degradation.It was established that metal ions were not directly involved in the catalysis of glycolipids in the short-term, however some metal ions were indirectly implicated in their degradation due to their ability to form acid solutions. Acid hydrolysis was established as the principle mechanism for glycan chain degradation. In general it was found that the glycan chain primarily lost its fucose groups (in no particular order) and was then followed by sequential degradation of the remaining glycan chain. The glycan chain also appeared to have a protective function on the ceramide moiety. Degradation of globoside established a simple sequential pathway of glycan chain reduction from the non-reducing end. Blood group glycolipids ALeb and Leb first lost their fucose side groups followed by sequential reduction of the glycan chain. Although not fully controllable, degradation of Leb was able to produce Lea, Led and Lec. In contrast degradation of ALeb did not produce any Lea or Led. Instead A-type 1 and two novel A-like structures, 'linear A' and 'GalNAc-Lea' were generated. Lec was only produced from ALeb in extremely acidic conditions. This research established the ability to generate, by acid hydrolysis, a range of rare and "unnatural" novel glycolipids from more commonly available structures. It is of interest that the so-called unnatural glycolipids obtained from the acid hydrolysis of ALeb may, in theory, occur naturally in the acid environment of the stomach, and as such could have the potential to be implicated in disease. It is probable that by applying the principles learned here, a range of novel and natural structures suitable for use in the study of biological interactions can be obtained.

Blood group glycolipids are important tools in the study of microbial receptor interactions and other biological phenomena. Presently blood group glycolipids of interest are isolated from biological samples. However, all glycolipids are not readily available due to the low frequency of some phenotypes in the general population. The ability to acquire the rare glycolipids from the degradation of common glycolipids would be a useful alternative to trying to obtain the molecules from biological sources.This research set out to establish the ability of blood group glycolipids to be degraded into useful glycolipids in a controlled manner by acid hydrolysis and possibly metal catalysis. The initial experiments investigated the degradation/hydrolysis of the more readily available glycolipid globoside with a range of salts and acids to establish degradation concepts such as; temperature, type of acid, acid concentration, and the role of metal ions in glycolipid degradation. These concepts then led to a series of degradation experiments with the blood group glycolipids Leb and ALeb. These glycolipids were incubated with a range of acid concentrations and varying temperatures. Thin layer chromatography separation and chemical and immunochemical staining were the main methods used to identify the products of degradation.It was established that metal ions were not directly involved in the catalysis of glycolipids in the short-term, however some metal ions were indirectly implicated in their degradation due to their ability to form acid solutions. Acid hydrolysis was established as the principle mechanism for glycan chain degradation. In general it was found that the glycan chain primarily lost its fucose groups (in no particular order) and was then followed by sequential degradation of the remaining glycan chain. The glycan chain also appeared to have a protective function on the ceramide moiety. Degradation of globoside established a simple sequential pathway of glycan chain reduction from the non-reducing end. Blood group glycolipids ALeb and Leb first lost their fucose side groups followed by sequential reduction of the glycan chain. Although not fully controllable, degradation of Leb was able to produce Lea, Led and Lec. In contrast degradation of ALeb did not produce any Lea or Led. Instead A-type 1 and two novel A-like structures, 'linear A' and 'GalNAc-Lea' were generated. Lec was only produced from ALeb in extremely acidic conditions. This research established the ability to generate, by acid hydrolysis, a range of rare and "unnatural" novel glycolipids from more commonly available structures. It is of interest that the so-called unnatural glycolipids obtained from the acid hydrolysis of ALeb may, in theory, occur naturally in the acid environment of the stomach, and as such could have the potential to be implicated in disease. It is probable that by applying the principles learned here, a range of novel and natural structures suitable for use in the study of biological interactions can be obtained.

Helicobacter pylori (H. pylori) is a human-specific gastric pathogen which is responsible for a spectrum of diseases ranging from superficial gastritis to gastric and duodenal ulceration, and which is also highly associated with gastric cancer. The pathogenesis of severe gastric disorders caused by H. pylori is multifactorial and involves complex interactions between the microbe and the gastric mucosa. H. pylori expresses several adhesion proteins. These molecules have important roles in the establishment of persistent infection and chronic inflammation, which cause tissue damage. The aim of this thesis was to study the attachment of this bacterium to human gastric epithelium, mediated by blood group antigens in both health and disease. One of the bestcharacterized H. pylori adhesins is the histo-blood group antigen binding adhesin (BabA), which binds specifically to the Lewis b antigen (Leb) in the gastric mucosa. A protective mucus layer lines the stomach. The mucosal glycosylation patterns (GPs) vary between different cell lineages, different locations along the gastrointestinal (GI) tract and different developmental stages. In addition, GPs undergo changes during malignant transformation. MUC5AC is a mucin molecule produced by the surface epithelium. Three distinctly different types of human gastrointestinal tissue were studied by bacterial adherence analysis in situ. MUC5AC is the most important carrier of Leb and the new results demonstrate that it forms major receptors for H. pylori adherence. By analysing an H. pylori babA-deletion mutant, a novel adhesin-receptor binding mode was found. Surprisingly, the mutant bound efficiently to both human gastric mucosa and to gastric mucosa of Leb transgenic mice. The sialylated and fucosylated blood group antigen, sialyl-dimeric-Lewis x (sdiLex), was structurally identified as the new receptor. A positive correlation was found between adherence of H. pylori to sialyl-Lewis x (sLex) and elevated levels of inflammation response in the human gastric mucosa. These results were supported by detailed analysis of sialylated and fucosylated blood group antigen glycosylation patterns and, in addition, in situ bacterial adherence to gastric mucosa of experimentally challenged Rhesus monkey. The cognate sialic acid-binding adhesin (SabA) was purified by the retagging technique, and the corresponding sabA-gene was identified. H. pylori lipopolysaccharide (LPS) contains various Lewis blood group antigens such as Lewis x (Lex) and Lewis y (Ley). Additional bacterial adherence modes, which are independent of the BabA and/or SabA adhesins, could possibly be mediated by Lex interactions. Adherence of a clinical isolate and its corresponding Lex mutant to human gastric mucosa with various gastric pathologies was studied in situ. The results suggest that H. pylori LPS plays a distinct but minor role in promotion of bacterial adhesion. Taken together, the results suggest mechanisms for continuous selection of H. pylori strains, involving capacity to adapt to changes in the local environment such as shifts in cell differentiation and associated glycosylation patterns. Adherence of H. pylori is dependent on both the BabA and the SabA adhesin. Multi-step dependent attachment mechanisms may direct the microbes to distinct ecological niches during persistent infections, driving the chronic inflammation processes further toward the development of peptic ulcer disease and/or malignant transformation. Key words: H. pylori, BabA, adhesin, Lewis b, MUC5AC, sialyl-dimeric-Lewis x, chronic inflammation, SabA, Lewis x, LPS.