Thermal behavior of synthetic sphingomyelin-cholesterol dispersions

The thermotropic behavior of aqueous dispersions of palmitoylsphingomyelin-cholesterol and lignoceryl-sphingomyelin-cholesterol mixtures has been examined by high-sensitivity differential scanning calorimetry. When less than 25 mol % cholesterol is mixed with either sphingomyelin, the calorimetric e...

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Bibliographic Details
Published in:Biochemistry (Easton) 1979-05, Vol.18 (10), p.2112-2117
Main Authors: Estep, T. N, Mountcastle, D. B, Barenholz, Y, Biltonen, R. L, Thompson, T. E
Format: Article
Language:English
Subjects:
animal science
Animals
Calorimetry, Differential Scanning
Cholesterol
Fatty Acids - analysis
Humans
livestock
Membranes, Artificial
Sphingomyelins
Structure-Activity Relationship
Temperature
Thermodynamics
zoology
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Summary:The thermotropic behavior of aqueous dispersions of palmitoylsphingomyelin-cholesterol and lignoceryl-sphingomyelin-cholesterol mixtures has been examined by high-sensitivity differential scanning calorimetry. When less than 25 mol % cholesterol is mixed with either sphingomyelin, the calorimetric endotherm is composed of a sharp and a broad component. The sharp-component enthalpy change decreases as the mole percent cholesterol increases with the extrapolated zero enthalpy point being 25 to 30 mol %. With palmitoylsphingomyelin, the temperature of maximum heat capacity of the sharp component decreases monotonically with increasing cholesterol content, while the lignocerylsphingomyelin sharp-component maximum remains constant until more than 20 mol % sterol is present. The broad-component enthalpy change maximizes at 3--4 kcal/mol between 10 and 20 mol % cholesterol and decreases as the ratio of cholesterol is increased or decreased from this range for both sphingomyelins. The results are compared with those from a previous study on dipalmitoylphosphatidylcholine-cholesterol mixtures and are interpreted as evidence for the coexistence of cholesterol-rich and cholesterol-poor phases.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00577a042