Crystal state and solution conformation of the B blood group trisaccharide a-l l-Fucp-(132)-[a-d d-Galp]-(133)]-b-d d-Galp-OCH 3Albin Otter, Raymond U. Lemieux, Richard G. Ball, Andre  P. Venot, Ole Hindsgaul and David R. Bundle Department of Chemistry, University of Alberta, Edmonton, CanadaThe crystal structure of the human B blood group related trisaccharide a-l-Fucp-(132)-[a-d-Galp]-(133)-b-dGalp-OCH 3 (1) has been determined. The solution structure of 1 was studied by two-dimensional NMR techniques at 600 MHz in D 2 O solution and the conformational properties were analyzed in terms of the torsional angles f H and c H , derived from 3 J CH coupling constants, and 10 inter-residue proton±proton distances. 3 J CH could be accurately measured by a recently introduced two-dimensional heteronuclear correlation experiment (EXSIDE). The nuclear Overhauser enhancement-derived distances and the calculated torsion angles were compared with the same information available from the crystal structure. The agreement is excellent, indicating that the trisaccharide adopts a restricted conformation in solution, which was also predicted by the Hard Sphere Exo-Anomeric forcefield. The data of 1 are complemented by NMR studies of the closely related a-l-Fucp- (132)Keywords: B blood group antigenic determinant; carbon-proton long-range coupling constants; conformation in solution and in the crystal; torsional angles; X-ray crystallography.The human A and B blood group antigenic determinants are the major isoantigens of importance to blood transfusion and tissue transplantation. The conformation of the B blood group trisac- (Fig. 1) was concluded to be relatively rigid, first by Lemieux et al. [1,2] and later confirmed in various solvents for closely related molecules by Bush et al. [3,4]. There has been debate as to what extent oligosaccharides in general can be treated as substantially rigid molecules [5,6]. Their conformational properties have therefore been extensively probed by both theoretical and experimental methodologies. The latter are in general restricted to NMR studies in solution but the inherent time-averaging of the inter-proton distances always poses a problem [7]. Crystallography can provide a firm indication of a conformational preference but only relatively limited information is available for oligosaccharides in the crystalline form, primarily because many of the oligosaccharides of interest have resisted attempts to form useful crystals.In this work, we report the crystal structure of the human blood group trisaccharide 1. We also describe conformational studies performed on 1. It was previously noted that the glycosidic torsional angles deduced from preliminary crystal structure data agreed with calculation and NMR experiments [8]. The details of the crystal structure are reported here in conjunction with a thorough examination of its conformational preference in D 2 O solution using modern NMR techniques at 600 MHz.Despite the limited instrumentation available 20 years ago, evidence was obtained, that the...