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Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate, C 13 H 24 O 11 ·H 2 O, (I), was obtained via spontaneous transformation of methyl β-lactoside methanol solvate, (II), during air-drying. Cremer–Pople puckering parameters indicate that the β-D-Gal p (β-D-galactopyranosyl) and β-D-Glc p (β-D-glucopyranosyl) rings in (I) adopt slightly distorted 4 C 1 chair conformations, with the former distorted towards a boat form ( B C1,C4 ) and the latter towards a twist-boat form ( O5 S C2 ). Puckering parameters for (I) and (II) indicate that the conformation of the βGal p ring is slightly more affected than the βGlc p ring by the solvomorphism. Conformations of the terminal O -glycosidic linkages in (I) and (II) are virtually identical, whereas those of the internal O -glycosidic linkage show torsion-angle changes of 6° in both C—O bonds. The exocyclic hydroxymethyl group in the βGal p residue adopts a gt conformation (C4′ anti to O6′) in both (I) and (II), whereas that in the βGlc p residue adopts a gg ( gauche – gauche ) conformation (H5 anti to O6) in (II) and a gt ( gauche – trans ) conformation (C4 anti to O6) in (I). The latter conformational change is critical to the solvomorphism in that it allows water to participate in three hydrogen bonds in (I) as opposed to only two hydrogen bonds in (II), potentially producing a more energetically stable structure for (I) than for (II). Visual inspection of the crystalline lattice of (II) reveals channels in which methanol solvent resides and through which solvent might exchange during solvomorphism. These channels are less apparent in the crystalline lattice of (I).
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Preferred conformations of lipooligosaccharides and oligosaccharides of Moraxella catarrhalis
Abstract Moraxella catarrhalis (M. catarrhalis) is a pathogenic gram-negative bacterium that causes otitis media and sinusitis in children. Three major serotypes A, B and C are identified to account for approximately 95% of the clinical isolates. Understanding the conformational properties of different serotypes of M. catarrhalis provides insights into antigenic determinants. In this work, all-atom molecular dynamics simulations were conducted for M. catarrhalis lipooligosaccharide (LOS) bilayer systems and oligosaccharides (OS) in water solution to investigate the conformational similarities and differences of three serotypes. For up to 10 neutral monosaccharides in the core part, the conformational ensembles described by the pair-wise root mean square deviation distributions are similar among the three serotypes of either the LOS or OS. At the central β-($$1\to4$$)-linkage, anti-$$\psi$$ conformation in conjunction with the gauche-gauche (g−) conformation of the central trisubstituted glucosyl residue is observed as the dominant conformation to sustain the structural characteristics of M. catarrhalis three types, which is further supported by calculated transglycosidic $${}^3{J}_{C,H}\Big({\psi}_H\Big)$$ of serotype A in comparison to experimental data. Interestingly, the conformational variability of three serotypes is more restricted for the OS in water solution than that in the LOS bilayer systems. The LOS–LOS interactions in the bilayer systems are responsible for the increased conformational diversity despite of tight packing. Solvent-accessible surface area analysis suggests that a trisaccharide attached to the β-($$1\to 6$$)-linked sugar in all three serotypes of LOS could be the common epitope and have the possibility to interact with antibodies.
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- PAR ID:
- 10170490
- Date Published:
- Journal Name:
- Glycobiology
- Volume:
- 30
- Issue:
- 2
- ISSN:
- 1460-2423
- Page Range / eLocation ID:
- 86 to 94
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/glycob/cwz086
