Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7692975 | Chemistry and Physics of Lipids | 2011 | 9 Pages |
Abstract
The crystal structure as well as the microstructure, i.e., size and strain, of crystallites of cholesteryl oleyl carbonate was determined from X-ray powder diffraction data. The X-ray line broadening was analyzed through the refinement of TCH-pseudo-Voigt function parameters (isotropic effects) and the refinement of multipolar functions, i.e., symmetrized cubic harmonics (anisotropic effects). The crystal structure turns out to be primitive monoclinic, space group Pc, type I monolayer having two molecules per unit cell with parameters: a = 18.921 ± 0.006 Ã
, b = 12.952 ± 0.003 Ã
, c = 9.276 ± 0.002 Ã
and β = 91.32 ± 0.03°. The average size of a well ground specimen of crystallites was 60 nm. The average micro-strain, e.g., 45 Ã 10â4 has been tentatively attributed to fatty chain conformational disorder. The unit cell parameters, including the lamellar thickness, of COC crystal is very closely similar to those of another, structurally similar cholesterol ester, e.g., cholesteryl oleate (CO) crystal, space group P21, type II monolayer. Type I monolayer structure has been established for COC on the basis of the intensity calculations of the XRD profiles of both CO and COC. The dipolar and structural disorder in a 4:1 molar, binary mixture of CO and COC can be accommodated in an induced smectic phase with a lamellar thickness, which is nearly equal to that of pure CO or pure COC.
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Authors
Pradip Das, Joyes De,