Pv. Dubovskii et al., A H-2-NMR COMPARATIVE-STUDY OF O-GLYCOSYL DIGLYCERIDE AND S-GLYCOSYLDIGLYCERIDE MEMBRANES, Biologiceskie membrany, 12(3), 1995, pp. 310-320
Physical properties of synthetic glyceroglycolipids possessing saturat
ed hydrocarbon chains, 1,2-di-[2-H-2(2)](-)palmitoyl-3-O-(beta w-D-gal
actopyranosyl) rac-glycerol and its S-glycoside analog were investigat
ed by H-2-NMR spectroscopy. It was shown that fully hydrated membranes
either annealed by long-term storage at -5 degrees C or not annealed,
which were formed of the investigated O- and S-glyceroglycolipids, di
splay in the 30-95 degrees C temperature range transitions of the type
s gel/liquid crystal and bilayer/nonbilayer structures. Different type
s of membranes exhibited different bilayer/nonbilayer structure transi
tions. S-glycerogiycolipid membranes show the bilayer/inverted hexagon
al phase transition, while O-glyceroglycolipid ones - the bilayer/isot
ropic phase and isotropic phase/inverted hexagonal phase transitions.
The H-2-NMR spectra for both types of membranes existing in the liquid
crystalline bilayer phase are characterized by a superposition of 3 s
ignales, whose intensities arranged in the Increasing order of quadrop
olar splitting magnitudes form a ratio of 1:1:2. The assignment of the
se signals to the acyl chains based on the T-1-relaxation measurements
, led us to the conclusion that the acyl chains of both O- and S-galac
tosyldiglycerides are conformationally inequivalent. The interdependen
ce of the conformational differences observed in the orientations of t
he 1st and 2nd acyl chains of O- and S-galactosyldiglycerides relative
to the bilayer director axis and the differences in the bilayer/nonbi
layer structure transitions exhibited by both types of the membranes i
nvestigated is discussed.