Journal of Lipid Research, Vol 37, 764-772, Copyright © 1996 by Lipid Research, Inc.
Monoacylglycerols alter the lipid composition and molecular mobility of phosphatidylcholine bilayers: 13C NMR evidence of dynamic lipid remodeling
E Boyle, DM Small, D Gantz, JA Hamilton and JB German
Department of Biophysics, Boston University School of Medicine, MA 02118, USA.
The physical effects of monoacylglycerols (MAG) in small unilamellar
vesicles composed of phosphatidyl-choline (PC), triolein, cholesterol, and
varying amounts of monopalmitin and monoolein were studied by 13C- NMR. The
signal to noise ratio of the carbonyls of PC and triolein were enhanced by
the addition of 1,2-di-[1-13C]palmitoylphosphatidylcholine and
tri-[1-13C]oleoylglycerol. The linewidths of the carbonyl-13C, choline
methyl, olefinic carbon, and terminal methyl resonances were measured
digitally from vesicles with 0 to 42 mol % of MAG. Significant increases in
the linewidth of carbonyl (P < 0.05), olefinic and terminal methyl
carbons (P < 0.01) of vesicles containing 42 mol % monopalmitin
indicated that these groups experienced restricted molecular mobility at
high monopalmitin concentrations. However, more striking was the apparent
displacement of triolein from the surface environment of PC bilayers to an
oil-like environment in systems containing only 8 mol % monopalmitin.
Displacement of triolein from the surface by monoolein occurred only above
15 mol %. Thus, saturated and monounsaturated monoacylglycerols, natural
products of lipoprotein metabolism, dynamically alter both the lipid
composition and molecular mobility of lipoprotein surfaces in distinct
ways.