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Proton NMR Study of the Trimannosyl Unit in a Pentaantennary N-Linked Decasaccharide Structure. Complete Assignment of the Proton Resonances and Conformational Characterization

1995; Wiley; Volume: 228; Issue: 3 Linguagem: Inglês

10.1111/j.1432-1033.1995.tb20328.x

1432-1033

Tomohiko Taguchi, Ken Kitajima, Y. Muto, Shigeyuki Yokoyama, Sadako Inoue, Yasuo Inoue,

Enzyme Production and Characterization

The chemical shifts of all the ring protons of the three Man residues in a pentaantennary glycan chain have been unambiguously assigned by two-dimensional proton nuclear magnetic resonance (1H-NMR) spectroscopic methods. The study, using chemical shift and J values on the conformation of the trimannosyl unit, revealed that the rotamer about the C5-C6 bond of the alpha 1-->6 linkage in the sequence of Man alpha 1-->6Man beta 1--> is predominantly confined to a gauche-gauche rotamer (omega = 180 degrees, omega = O6-C6-C5-H5) and not to a gauche-trans rotamer (omega = -60 degrees). We do not know of any previous demonstration that the dihedral angle omega (O6-C6-C5-H5) in Man alpha 1-->6Man beta 1--> is preferentially 180 degrees in complex-type N-linked glycans having no bisecting GlcNAc residue.