The Incorporation of Labile Protons into Multidimensional NMR Analyses: Glycan Structures Revisited
| Autor: | Marcos D. Battistel, Hugo F. Azurmendi, Lucio Frydman, Darón I. Freedberg, Mihajlo Novakovic, Maria Grazia Concilio |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Glycan
Aqueous solution biology Chemistry General Chemistry 010402 general chemistry 01 natural sciences Biochemistry Acceptor Article Catalysis 0104 chemical sciences Molecular dynamics Colloid and Surface Chemistry Computational chemistry biology.protein Spectroscopy Two-dimensional nuclear magnetic resonance spectroscopy Homotetramer |
| Zdroj: | Journal of the American Chemical Society |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.1c04512 |
| Popis: | Glycan structures are often stabilized by a repertoire of hydrogen-bonded donor/acceptor groups, revealing longer-lived structures that could represent biologically relevant conformations. NMR provides unique data on these hydrogen-bonded networks from multidimensional experiments detecting cross-peaks resulting from through-bond (TOCSY) or through-space (NOESY) interactions. However, fast OH/H2O exchange, and the spectral proximity among these NMR resonances, hamper the use of glycans’ labile protons in such analyses; consequently, studies are often restricted to aprotic solvents or supercooled aqueous solutions. These nonphysiological conditions may lead to unrepresentative structures or to probing a small subset of accessible conformations that may miss “active” glycan conformations. Looped, projected spectroscopy (L-PROSY) has been recently shown to substantially enhance protein NOESY and TOCSY cross-peaks, for 1Hs that undergo fast exchange with water. This study shows that even larger enhancements can be obtained for rapidly exchanging OHs in saccharides, leading to the retrieval of previously undetectable 2D TOCSY/NOESY cross-peaks with nonlabile protons. After demonstrating ≥300% signal enhancements on model monosaccharides, these experiments were applied at 1 GHz to elucidate the structural network adopted by a sialic acid homotetramer, used as a model for α,2–8 linked polysaccharides. High-field L-PROSY NMR enabled these studies at higher temperatures and provided insight previously unavailable from lower-field NMR investigations on supercooled samples, involving mostly nonlabile nuclei. Using L-PROSY’s NOEs and other restraints, a revised structural model for the homotetramer was obtained combining rigid motifs and flexible segments, that is well represented by conformations derived from 40 μs molecular dynamics simulations. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|