title: Sialo-CEST: chemical exchange saturation transfer NMR of oligo- and poly-sialic acids and the assignment of their hydroxyl groups using selective- and HSQC-TOCSY.
abstract: Chemical exchange saturation transfer (CEST) is an NMR method that takes advantage of proton exchange between solute and solvent molecules in dynamic equilibrium, enabling the detection of the solute NMR signals with enhanced sensitivity. Herein, we report that the hydroxyl groups in a naturally occurring polysaccharide, α-2,8 polysialic acid in aqueous solution, yield very significant CEST effects even at 37°C where the resonances of the hydroxyl groups are not directly observed. We also report the assignments of the hydroxyl groups for the polymer and its oligomeric building blocks, from monomer to hexamer. We show that the same assignments can be made by either (1)H-(1)H TOCSY methods or (1)H-(13)C HSQC-TOCSY methods, to alleviate spectral overlap. Finally, we report the exchange rates of the OH groups with water and show how these rates can be used to select and fine-tune CEST effects.
authors.affiliation: School of Chemistry, Tel Aviv University, Levanon Street, Ramat Aviv, Tel Aviv 69978, Israel.
authors.forename: Hadassah
authors.initials: H
authors.lastname: Shinar
authors.affiliation: Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-428, Rockville, MD 20852, United States.
authors.forename: Marcos D
authors.initials: MD
authors.lastname: Battistel
authors.affiliation: Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-428, Rockville, MD 20852, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Mandler
authors.affiliation: Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-428, Rockville, MD 20852, United States.
authors.forename: Flora
authors.initials: F
authors.lastname: Lichaa
authors.affiliation: Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, HFM-428, Rockville, MD 20852, United States.
authors.forename: Darón I
authors.initials: DI
authors.lastname: Freedberg
authors.affiliation: School of Chemistry, Tel Aviv University, Levanon Street, Ramat Aviv, Tel Aviv 69978, Israel. Electronic address: navon@post.tau.ac.il.
authors.forename: Gil
authors.initials: G
authors.lastname: Navon
mesh_terms: D006878:Hydroxides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012794:Sialic Acids / Q000737:chemistry*
chemical_list: D006878:Hydroxides; D012794:Sialic Acids; C021319:polysialic acid; C031356:hydroxide ion
keywords: Chemical exchange saturation transfer (CEST); Exchange rate constants; Hydroxyl groups assignments; NMR; Polysialic acid; Sialic acid