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Study of the miscibility of cholesteryl oleate in a matrix of ceramide, cholesterol and fatty acid.
MedLine Citation:
PMID:  21756886     Owner:  NLM     Status:  Publisher    
Cholesteryl esters (CE) are not generally abundant but are ubiquitous in living organisms and have markedly different properties from cholesterol because of their acyl chain. The miscibility/immiscibility of CE with biological lipid structures is a key property for their functions. In this work we study the solubility of cholesteryl oleate (ChO) in a model of the stratum corneum lipid matrix composed of ceramide C16, cholesterol and palmitic acid in excess water. Experiments were done in conditions of fully ionized (pH=9.0) and fully neutralized fatty acid (pH=4.0), and differential scanning calorimetry of the ternary mixtures with added ChO at pH=9.0 clearly displayed a main transition with the same maximum temperature, peak shape, and enthalpy, suggesting that ChO was excluded from the remaining lipids. This technique is not conclusive at pH=4.0 because the transitions of the lipid matrix and ChO overlap. The insolubility of ChO at both pH values is supported by X-ray diffraction. Adding the ceramide:cholesterol:fatty acid lipid mixture to ChO did not change the X-ray pattern of the mixture nor that of the ChO. To supplement the above physical techniques, we applied (13)C MAS NMR spectroscopy with C-13 carbonyl-labeled ChO. A single (13)C carbonyl peak from the ChO at 171.5ppm was observed, indicating exposure to only one environment. The chemical shift was identical to pure ChO below and above the temperature of isotropic liquid formation. Taken together, our results lead to the conclusion that the solubility of ChO is negligible in the ceramide:cholesterol:fatty acid lipid mixture.
Sofia L Souza; Kevin J Hallock; Sérgio S Funari; Winchil L C Vaz; James A Hamilton; Eurico Melo
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-7-3
Journal Detail:
Title:  Chemistry and physics of lipids     Volume:  -     ISSN:  1873-2941     ISO Abbreviation:  -     Publication Date:  2011 Jul 
Date Detail:
Created Date:  2011-7-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0067206     Medline TA:  Chem Phys Lipids     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011. Published by Elsevier Ireland Ltd.
Instituto de Tecnologia Química e Biológica - UNL, Av. da República-EAN, 2780-157 Oeiras, Portugal.
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