There are several well-known examples where the sequencing of polymers has provided immense benefits. Today entire DNA genomes are being sequenced, bringing with them the prospect of a revolution in medicine and biology. Similarly, a new protein can have its polypeptide sequence read, with the result that the molecular detail of its structure can be determined and the detailed mechanism of its biological function revealed. The situation is very different for the third major class of biopolymers, the glycans (sugar-containing molecules - polysaccharides and glycosylated polymers in general), despite increasing recognition of their critical role in the biology of all life and their industrial importance. On the one hand, specific short sequences may be defined with submolecular precision, but on the other, beyond a dozen or so monomers the relationship between these sequences is lost and we must rely on bulk methods to describe the material. This often leaves those who wish to understand the multiple, critical roles played by polysaccharides with little of the molecular scale detail now taken for granted by molecular biologists. Examples of these beneficiaries include the food and pharmaceutical industries looking to develop new food and drug delivery formulations, medical researchers hoping to appreciate the role of glycopolymers in human health, or botanists and microbiologists studying the function of plant and bacterial cell walls in growth or pathogenic activity. This project exploits the recent development of a force-measuring microscope capable of, for the first time, mapping the distribution of defined oligomer (short polymer) sequences in single glycan polymers. It will do this by exploiting the phenomenon of rotaxanes - molecular rings threaded over a polymer chain. In this case, an atomic force microscope (AFM) probe picks up the ring (a cyclodextrin molecule) from its 'base' on a suitable polymer and slides it along and on to the glycan chain of interest, which is coupled to the rotaxane. Molecules known to recognise and bind to well-defined sequences within the polymer are allowed to interact with the polymer chain and form complexes; the ring is then passed along the chain and when it encounters a complex will 'unzip' it, removing the bound molecule. The mapping information comes from the magnitude of the interaction between the ring and each bound complex it encounters, along with the position along the chain at which the interaction occurs. By collecting this information from a large sample of individual polymers, a map of the distribution patterns of the known sequences is revealed. We have shown that this appealingly simple mechanical concept actually works for simple model polymers; now this project is designed to apply this entirely new sequencing tool to a medically and commercially highly significant glycan, alginate. Alginate is produced by seaweeds and also by bacteria, including Pseudomonas aeruginosa when it colonises the lung in cases of cystic fibrosis. Alginate produced by the bacteria in the lung forms a gel to protect the bacteria from immune responses and attacks but also contributes to obstructions in the airways of the lung which may be fatal. Median life expectancy of cystic fibrosis sufferers is 35 years. Alginate gels form in the presence of calcium and other divalent cations due to the formation of so-called 'egg box' junction zones between aligned pairs of guluronic acid (oligoG) sequences. The minimum length of oligoG required to form a stable junction zone is not known and thus this project aims to determine both this minimum length and its distribution within well-characterised samples of alginate polymers.