Solid state 13C NMR investigation of lipid ligands in V-amylose inclusion complexes

The characteristics of the ligands in inclusion complexes formed from stearic, palmitic, oleic, linoleic, linolenic and docosahexaenoic acids, glycerol monooleate (GMO), glycerol monopalmitate (GMP) and lysophosphatidylcholine (LPC) have been studied by C-13 NMR in dry and hydrated forms of the complexes, with C-13 labels being used for the carboxyl and C-1(3) glycerol carbons in stearic acid and GMO, respectively. C-13 NMR provides definitive proof that V-amylose inclusion complexes have been formed with the mono-carboxylic fatty acids of varying degrees of unsaturation, GMO, GMP and LPC. The chemical shift of the mid-chain methylenes in stearic acid moves about 1.5 ppm upheld upon complexation with the H-1 rotating frame relaxation times becoming identical for the lipid and amylose. With the exception of docosahexaenoic acid, the mid-chain methylenes inside the V-helical segments have essentially the same chemical shift for all the other unsaturated fatty acids and lipids investigated. The cross-polarisation dynamics for the carboxyl and glycerol groups in stearic acid and GMO, respectively, have indicated that these bulky polar groups occupy highly mobile conformations in the hydrated complexes which must lie outside the V-helical segments adjacent to the amorphous domains. (C) 1998 Elsevier Science Ltd. All rights reserved.