Structures of mono-unsaturated triacylglycerols. III. The beta-2 polymorphs of trans-mono-unsaturated triacylglycerols and related fully saturated triacylglycerols.
The beta-2 crystal structures of a series of saturated and trans-mono-unsaturated triacylglycerols (TAGs) have been solved from high-resolution powder synchrotron diffraction data. The series comprises symmetric as well as asymmetric even-numbered TAGs and the trans-mono-unsaturated ones all have a single elaidoyl chain. The structures have been solved with the direct-space parallel-tempering program FOX and refined with the Rietveld program GSAS. The beta-2 structures all crystallized in the space group P\bar 1 with the same molecular conformation. Within the resolution of the data no significant difference in packing or conformation is observed between trans-mono-unsaturated TAGs and saturated (stearoyl or palmitoyl) chain-containing analogues, in spite of the lower melting points of the former. An analysis of the position of the stepped methyl end-plane in the various subgroups of TAGs confirms most but not all suppositions found in the literature.
van Mechelen
Jan B
JB
University of Amsterdam, HIMS/FNWI/Kristallographie, Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands. janvm@science.uva.nl
Peschar
Rene
R
Schenk
Henk
H
D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D033362:Powder Diffraction; D014280:Triglycerides / Q000737:chemistry*
D014280:Triglycerides