th  - 1988 - 51st ENC Conference

THU 8:55 ]
MULTINUCLEAR EXPERIMENTS FOR THE DETERMINATION OF
OLIGOSACCHARIDE STRUCTURE IN LIQUID CRYSTAL PHASES: J. H. Prestegard~,
Preetha Ram, and L. T. Mazzola, Department of Chemistry, Yale University,
New Haven, CT 06511.
The dependence of quadrupole and magnetic dipole splittings on orientation
of internuclear vectors relative to applied magnetic fields can, in
principle, provide a great deal of information on the conformation and
orientation of molecules in llquld crystal phases. In practice, however,
it is difficult to obtain a sufficient number of independent spllttlngs to
reduce the ambiguity inherent in the multlvalued solutions for spllttlngs
in terms of angles, and to eliminate order parameters which scale
spllttlngs in these environments.
We will show that in some cases, it is possible to obtain sufficient
information by combining data from 2H quadrupole spllttlngs, 13C-IH dipolar
spllttlngs, and IH-IH dipolar spllttlngs. Observation of these spllttlngs
is facilitated by use of liquid crystal phases which are relatively free of
background signals, and use of experiments which exploit unique
spectroscopic properties of quadrupole and dipole couplings. In other
cases, spectroscopic information can be supplemented with energetic
descriptions of molecular conformations contained in molecular mechanics
and molecular dynamics programs. Examples of structure determination on
surface associated dlsaccharides and membrane anchored glycoltpids will be
given.
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