NMR and conformational studies of linear and cyclic oligo-(1→6)-β-d-glucosamines

Abstract

The conformational behavior of a series of linear and cyclic oligo-(1→6)-β-D-glucosamines and their N-acetylated derivatives, which are related to fragments of natural poly-N-acetylglucosamine, was studied by theoretical molecular modeling and experimental determination of transglycosidic vicinal coupling constants 3JC,H and 3JH,H. Molecular dynamics simulations were performed under several types of conditions varying in the consideration of ionization of amino groups, solvent effect and temperature. Neural network clustering and asphericity calculations were performed on the basis of molecular dynamics data. It was shown that disaccharide fragments in the studied linear oligosaccharides were not rigid, and tended to have several conformers, thus determining the overall twisted shape with helical elements. In addition, it was found that the behavior of C5–C6 bond depended significantly upon the simulation conditions. The cyclic di-, tri-, and tetrasaccharides mostly had symmetrical ring-shaped conformations. The larger cycles tended to adopt more complicated shapes, and the conformational behavior of their disaccharide fragments was close to that in the linear oligosaccharides.

Modification and periplasmic translocation of the biofilm exopolysaccharide poly-β-1,6- N -acetyl- d -glucosamine

“…It is quite possible that this conserved patch of residues initially binds PNAG and the force of biosynthesis moves the polymer in an extended conformation along the de-N-acetylation site to the IDL. Structural studies on β-1,6-GlcN oligomers show they have conformational freedom with the tendency to adopt stacked or helical structures (25). GlcNAc residues in −2 to +1 de-N-acetylation subsites show a stacked conformation (Fig.…”

Synthesis of Multivalent Carbohydrate‐Centered Glycoclusters as Nanomolar Ligands of the Bacterial Lectin LecA from Pseudomonas aeruginosa

“…Recently, we designed a family of cyclic oligo‐(1→6)‐β‐ D ‐glucosamines consisting of two to seven monosaccharide units24, 25 and two cyclotetrasaccharides comprising both glucosamine and glucose residues 26. These cyclic oligomers differ from the well‐known cyclodextrins, which have more conformational flexibility27 but lack a distinct hydrophobic cavity. The presence of amino groups suitable for conjugation allows these cyclic oligosaccharides to be regarded as a new type of functionalized scaffolds for the development of multivalent glycoconjugates.…”

Gas-Phase Fragmentation of Cyclic Oligosaccharides in Tandem Mass Spectrometry

“…Recently, Chizhov et al reported extensive studies concerning high resolution tandem mass spectrometry (ESI QqTOF) of cyclooligo-β-(1→6)- d -glucosamines, cyclooligo-β-(1→6)- d - N -acetyl-glucosamines (from two to seven Glc N or Glc N Ac residues, respectively, 19a , b – 24a , b , Figure 16) [70], and mixed isomeric β-(1→6)-linked cyclic tetrasaccharides of the Glc p 2 Glc pN 2 composition ( 25 and 26 , Figure 17) [71]. Synthetic details for the preparation, structural and conformational analysis of cyclo-β-(1→6)- d -glucosamines 19a , b – 24a , b were described in [72,73,74].…”

“…Structural formulas of cyclooligo-β-(1→6)- d -glucosamines 19a – 24a and cyclooligo-β-(1→6)- d - N -acetylglucosamines 19b – 24b [70,72,73,74] (reproduced from [70] with permission of Springer Nature).…”