Evidence for Helical Structure in a Tetramer of α2-8 Sialic Acid: Unveiling a Structural Antigen

Abstract

Characteristic hydrogen bonding (H-bonding) patterns define secondary structure in proteins and nucleic acids. We show that similar patterns apply for α2-8 linked SiA (sialic acid) in H2O; and that H-bonds define its structure. A 15N,13C α2-8 SiA tetramer was used as a model system for the polymer. At 263K, we detected intra-residue through-bond J couplings between 15N and C8 for residues I, II and III of the tetramer, which indicate H-bonds between the 15Ns and the O8s of these residues. Additional J couplings between the 15Ns and C2s of the adjacent residues confirm the putative H-bonds. The NH groups showing this long-range correlation also experience slower 1H/2H exchange rate. Additionally, detection of couplings between H7 and C2 for residues II and III imply that the conformations of the linkers between these residues are different than the monomer's. These structural elements are consistent with two left handed helical models: 1) two residues per turn (24 helix) and 2) four residues per turn (14 helix). To discriminate between models, we resorted to 1H, 1H NOEs. The 24 helical model is in better agreement with the experimental data, for which all of the observed NOEs are predicted. On the other hand, for the 14 helix 87% of the observed intra-residue NOEs are predicted. In this report we provide direct evidence of H-bonding for a tetramer of α2-8 linked SiA and show how H-bonds can be a determining factor for shaping the carbohydrate three-dimensional structure.

Uncovering Nonconventional and Conventional Hydrogen Bonds in Oligosaccharides through NMR Experiments and Molecular Modeling: Application to Sialyl Lewis-X

“…We detected a non-conventional C-H•••O Hbond in sLe X -5 using long-range HSQC (lr-HSQC) experiments, which allow efficient evolution to detect small heteronuclear 1 H, 13 C couplings (SI), like those expected for Hbonds. As Hbond signals are sensitive to temperature, 6 we performed experiments at various temperatures to find the best condition for detection.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2011–2012

“…Anti-inflammatory effects (Chung et al, 2012a) Mannosides with hydrophobic substituents TOF Synthesis as DC-SIGN antagonists (Obermajer et al, 2011) 15 N, 13 C 2 8-sialic acid oligomers TOF Evidence for helical structure in a tetramer of 2 8 sialic acid (Battistel et al, 2012) Oligo( -D-glycosyl phosphate) derivatives TOF Use of a phosphoramidite method via boranophosphate intermediates (Fujita et al, 2011b) Orthogonally protected disaccharide MALDI For synthesis of 6-sulfated derivatives with terminal ethylamine (Liu et al, 2012g) Pustulooligosaccharides ( (Yang et al, 2011f) Tri-, penta-, and heptasaccharides, with orthogonally N-protected amino residues TOF Synthesis of four bifunctionalized orthogonally N-protected oligosaccharides derived from lactose and mannose, intended as cross-linking derivatives (Fyrner et al, 2012a) Poly-N-acetyllactosamineextended TOF (DHB) For recognition studies by human and avian influenza A virus hemagglutinins …”

Methods for Measuring Exchangeable Protons in Glycosaminoglycans

“…MD simulations also confirmed the presence of intermolecular hydrogen bonds between both glucose OH3 (donor) and fructose OH3 (acceptor), which was also detected by cross peaks arising from the 2 J OH-OH coupling using selective COSY experiments, demonstrating the potential of this experiment to study interactions between GAGs. Though this work used concentrations (50 mM and above) that are not generally feasible for GAG oligosaccharides, this limitation could be overcome through the use of isotopically labeled compounds [28].…”