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Abstract
Carbohydrate polymers comprise a diverse array of biological molecules which play roles with both commercial and medical importance. Furthermore, they comprise key structural components in numerous biological organisms. These include critical components of gram-negative bacterial cell wall membranes, while also being the dominant structural component of plant and fungal cell walls. Of importance in biological dogma is the notion that structure plays a critical role in determining function. Given this, much analytical effort has been expended in developing methods to determine the structure of different polysaccharides. One result of these efforts is an appreciation for the fact that polysaccharide structures comprise a wide range of sugar substrates, linkages, and chemical modifications. Full structural elucidation usually requires the use of a myriad of different analytical techniques. Some of these analytical tools include analyses to determine the types of monosaccharide present, analyses to assess the linkages of the different monosaccharides, and the more complex mass spectrum (MS) and nuclear magnetic resonance (NMR) analyses to determine the full structure of the polysaccharide. While full structural elucidation is generally the end goal, some samples prove resistant to traditional analysis and require the development of new methodologies.
Here, we present the results of structural determination of bacterial polysaccharides and the development of analytical methods for the analysis of polysaccharides which are resistant to traditional analysis. This work demonstrated that the agriculturally important plant pathogen Liberibacter crescens contains an unusual lipopolysaccharide (LPS) consisting of a traditional rhizobia lipid A but having an unusual core structure and O-chain architecture. In addition, the structure allows us to glen functional insights into the biology of uncultured members of the Candidatus Liberibacter genus. We also present work detailing our efforts to generate composition data from insoluble samples using new analytical methods. Traditionally, lack of solubility has been a significant impediment to the analysis of certain types of polysaccharides. We employ methylation as a way of solubilizing polysaccharides in order to allow for a more comprehensive analysis of plant cell walls.