TY - JOUR
T1 - Polymorphic behavior of 1,2-dipalmitoyl-3-lauroyl(PP12)- and 3-myristoyl(PP14)-sn-glycerols
AU - Kodali, D. R.
AU - Atkinson, D.
AU - Small, D. M.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1990
Y1 - 1990
N2 - The polymorphic behavior and molecular packing in different polymorphic forms of stereospecific triacylglycerols, 1,2-dipalmitoyl-3-lauroyl-sn-glycerol (PP12) and 1,2-dipalmitoyl-3-myristoyl-sn-glycerol (PP14) were examined by X-ray diffraction, differential scanning calorimetry, infrared and Raman spectroscopy techniques. The molecular packing and the polymorphic behavior of the metastable forms of these two compounds are very similar. In both compounds the isotropic liquid, on quenching, crystallizes into a hexagonally packed α-phase. The long spacing periodicity of the α-phase indicates a tilted bilayer structure to compensate the voids created by the short acyl chains. Upon heating, the α-phase converts into an orthorhombic perpendicular (O is perpendicular to) β'2-phase. The β'2-phase, on further heating, exothermally converts to β'1-phase with slightly different O is perpendicular to subcell. On incubation of PP12 near the melting temperature of β'1-phase, there is a slow (hours) conversion to a β-phase with triclinic parallel (T//) packing. However the β'1-phase of PP14 is the most stable structure and the β-phase is absent. The thermodynamic parameters of the O is perpendicular to packings of these compounds compared to those of the higher homologue, tripalmitoylglycerol, suggest that the O is perpendicular to subcell is more stable in PP12 and PP14. The X-ray diffraction long spacings indicate that all the polymorphic forms of these compounds pack in a bilayer structure. The vibrational spectra confirm the lateral chain packing and inter- and intra-molecular order/disorder in the various polymorphic forms. The Raman and infrared spectra further indicate pertrubation in the carbonyl and the end methyl plane regions of the β'-phases.
AB - The polymorphic behavior and molecular packing in different polymorphic forms of stereospecific triacylglycerols, 1,2-dipalmitoyl-3-lauroyl-sn-glycerol (PP12) and 1,2-dipalmitoyl-3-myristoyl-sn-glycerol (PP14) were examined by X-ray diffraction, differential scanning calorimetry, infrared and Raman spectroscopy techniques. The molecular packing and the polymorphic behavior of the metastable forms of these two compounds are very similar. In both compounds the isotropic liquid, on quenching, crystallizes into a hexagonally packed α-phase. The long spacing periodicity of the α-phase indicates a tilted bilayer structure to compensate the voids created by the short acyl chains. Upon heating, the α-phase converts into an orthorhombic perpendicular (O is perpendicular to) β'2-phase. The β'2-phase, on further heating, exothermally converts to β'1-phase with slightly different O is perpendicular to subcell. On incubation of PP12 near the melting temperature of β'1-phase, there is a slow (hours) conversion to a β-phase with triclinic parallel (T//) packing. However the β'1-phase of PP14 is the most stable structure and the β-phase is absent. The thermodynamic parameters of the O is perpendicular to packings of these compounds compared to those of the higher homologue, tripalmitoylglycerol, suggest that the O is perpendicular to subcell is more stable in PP12 and PP14. The X-ray diffraction long spacings indicate that all the polymorphic forms of these compounds pack in a bilayer structure. The vibrational spectra confirm the lateral chain packing and inter- and intra-molecular order/disorder in the various polymorphic forms. The Raman and infrared spectra further indicate pertrubation in the carbonyl and the end methyl plane regions of the β'-phases.
KW - X-ray diffraction
KW - differential scanning calorimetry
KW - infrared and Raman spectroscopy
KW - molecular packing
KW - phase behavior
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M3 - Article
C2 - 2079608
AN - SCOPUS:0025013191
SN - 0022-2275
VL - 31
SP - 1853
EP - 1864
JO - Journal of lipid research
JF - Journal of lipid research
IS - 10
ER -