Structure cristalline de la N-acétyl-α-D-galactosamine

Abstract

Crystals of N-acetylgalactosamine are monoclinic with unit-cell constants a=9.159 (4), b= 6.320 (2), c=9.208 (4) /~, ,8=107.88 (6) ° and space group P2~. The structure has been determined by direct methods and refined by least-squares calculations to a final R of 0.04. The main features of the molecular structure are the shortening of the anomeric bond in agreement with the observation on other saccharides, the electron delocalization of the amide group similar to that of N-acetylglucosamine and oligopeptides, and the existence of an intramolecular hydrogen bond.

Vacuum-Ultraviolet Circular Dichroism Analysis of Glycosaminoglycans by Synchrotron-Radiation Spectroscopy

“…According to the X-ray studies, the hydroxymethyl group at C-5 takes only the GT conformer in CS-A and GalNAc4Sul, 21,22) although this group takes GT and TG conformers in CH and the GG conformer in GalNAc. [17][18][19] These results suggest that the sulfate group at C-4 influenced the staggered conformations (GT, GG, and TG) of the hydroxymethyl group at C-5 to provide a more negative CD intensity for CS-A (or GalNAc4Sul) than for CH (or GalNAc), because the GT conformer could reduce the intensity of the CD spectrum of the ring oxygen electrons more strongly than any other conformer. 12) The electrostatic excitation of the sulfate group due to light absorption below 195 nm affects the -Ã transition of the carboxyl and acetamido groups below 205 nm, 5) but the difference in CD spectra between CH and CS-A is mainly attributable to the local changes in optical properties of the GalNAc moiety, because the carboxyl group is far from the sulfate group.…”

“…Therefore, such nonadditivity below 200 nm would be mainly due to the OH group at C-1 of GalNAc (which is in anomeric equilibrium) being fixed to the -linkage in CH. Furthermore, X-ray structural analyses have shown that the hydroxymethyl group at C-5 took the GG conformer in GalNAc, 17) but it took the GT or TG conformer in the GalNAc residue of CH. 18,19) Such preference for the GT and TG conformers would cause a more negative spectrum for CH than the sum of the spectra for GalNAc and GlcU below 200 nm, because the -anomer of galactose induces large negative CD bands below 190 nm for both GT and TG conformers of the hydroxymethyl group at C-5.…”

Molecular modeling of the conformational and sodium ion binding properties of the oligosaccharide component of ganglioside GM1

“…In preliminary 50 ps simulations of the GM1 oligosaccharide-sodium complex using dielectric constants of 80, 60,40,20, and 1, dissociation of the complex occurred at dielectric constants of 40 or higher. Dissociation was presumably due to the lack of explicit solvent, which is able to hinder the diffusion of ligands.…”

Structure cristalline de l'α-DL-fucopyrannose

“…Parmi les monosaccharides naturels, le galactose, le fucose, la N-ac&yl-galactosamine jouent, entre autres, un r61e prSpond6rant dans la constitution des d&ermi-nants antig6niques des groupes sanguins H, Aet B, aussi avons-nous 6lucid6 les structures cristallines de la N-ac&yl-a-D-galactosamine (Neuman, Gillier-Pandraud & Longchambon, 1973;Neuman, Gillier-Pandraud, Longchambon & Rabinovich, 1975), de l'a-D-galactose (Ohanessian & Gillier-Pandraud, 1976), du /~-Dgalactose et de l'a-L-fucose (Longchambon, Ohanessian, Avenel & Neuman, 1975). En raison de la mosaicit6 des cristaux de ce dernier compos6, la largeur des pics &ait telle que leur r6solution devenait tr6s mauvaise.…”