Collaborative Research: Conformational Equilibria of Biologically Important Saccharides and Related Biomolecules

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With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Anthony Serianni from the University of Notre Dame and Dr. Robert Woods from the University of Georgia to investigate the three-dimensional properties of sugar molecules, or saccharides, in solution. Saccharides embedded in cell surfaces play critical roles in biology. In humans, they are attached to soluble and membrane associated proteins and lipids, and their biological roles include cell-to-cell and immune recognition. While it is well known that the structural properties of saccharides correlate with their biological functions, it remains difficult to assign these structural details in solution by experimental methods. This difficulty has led to a heavy reliance on theoretical methods to assign structures even though these methods have been difficult to validate experimentally. This project aims to solve this problem by developing and applying a new experimental technique to determine populations of flexible domains in saccharides in solution, including the linkages connecting them together in polymers and linkages that attach them to other biomolecules. The experiment-derived information obtained can be compared to what is obtained from theory to test and/or validate the latter. Senior researchers, graduate students and undergraduates with interests and expertise in experimental and computational science collaborate to achieve the objectives of the project. This work provides valuable new tools to determine molecular structure that can be generally applied to any biomolecule in solution, including proteins and nucleic acids.This research project uses stable isotopically labeled oligosaccharides and glycopeptides, nuclear magnetic resonance (NMR) spin-couplings, density functional theory calculations, circular statistics and X-ray crystallography to determine conformational populations of the flexible domains of oligosaccharides in solution. This experimental approach is possible because saccharides contain multiple NMR spin-couplings that report on the same conformational domain, allowing quantitative treatments that yield continuous single- and multi-state populational models. Once a given domain is parameterized (e.g., O- or N-glycosidic linkage), its conformational properties can be investigated in different structural contexts to determine the degree to which it adapts conformationally to environmental cues. Experimental models are compared to those obtained from molecular dynamics simulations to validate the latter. This work leads to new experiment-based conformational classifications of O-glycosidic linkages in oligosaccharides, and to a deeper understanding of the multiple factors that influence oligosaccharide conformation in solution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.