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Expeditious Synthesis of Bacterial Glycoconjugates
Suvarn S. Kulkarni
Department of Chemistry, IIT Bombay, Powai, Mumbai-400076
Bacterial glycoconjugates are comprised of rare D and L deoxy amino sugars, which are not present on the human cell surface. This peculiar structural difference allows discrimination between the pathogen and the host cell and offers avenues for target-specific drug discovery and carbohydrate-based vaccine development. However, they cannot be isolated with sufficient purity in acceptable amounts, and therefore chemical synthesis is a crucial step toward the development of these products.1 We recently established short and convenient methodologies for the synthesis of orthogonally protected bacterial D and L-deoxy amino hexopyranoside and glycosamine building blocks starting from cheaply available D-mannose and L-rhamnose.2-4 The one-pot protocols rely on highly regioselective nucleophilic displacements of triflates. These procedures have been applied to the synthesis of various bacterial glycoconjugates2-8 (Figure 1) as well as metabolic oligosaccharide engineering.7


1) Emmadi, M.; Kulkarni, S. S. Nat. Prod. Rep. 2014, 31, 870-879. 2) Emmadi, M.; Kulkarni, S. S. Nature Protocols 2013, 8, 1870-1889. 3) Sanapala, S. R.; Kulkarni S. S. J. Am. Chem. Soc. 2016, 138, 4938−4947. 4) Sanapala, S. R.; Kulkarni S. S. Org. Lett. 2016, 18, 3790–3793. 5) Podilapu, A. R.; Kulkarni, S. S. Org. Lett. 2014, 16, 4336-4339. 6) Sanapala, S. R.; Kulkarni, S. S., Chem. Eur. J. 2014, 20, 3578-3583. 7) Clark, E.; I.; Emmadi, M.; Krupp, K. L.; Podilapu, A. R.; Helble, J. D.; Kulkarni, S. S.; Dube, D. H. ACS Chem Biol 2016, 11, 3365-3373. 8) Podilapu, A. R.; Kulkarni, S. S. Org. Lett. 2017, 19, 5466-5469.

Synapses change their strength in response to specific activity patterns. This functional plasticity is assumed to be the brain’s primary mechanism for information storage. We combine optogenetic and chemogenetic control of synapses in rat hippocampal slice cultures with calcium and glutamate imaging of their spines and boutons. This approach enables us to perform all-optical quantal analysis of synaptic transmission, to induce long-term potentiation (LTP), long-term depression (LTD), or both forms of plasticity in sequence, to chronically manipulate activity and to follow the fate of individual synapses for 7 days. We ask how plasticity and activity are integrated at Schaffer collateral synapses over time. Our findings suggest that activity-dependent changes in the transmission strength of individual synapses are transient, but have long-lasting consequences for synaptic lifetime.