Membrane properties of D-erythro-N-acyl sphingomyelins and their corresponding dihydro species.
We have prepared acyl chain-defined D-erythro-sphingomyelins and D-erythro-dihydrosphingomyelins and compared their properties in monolayer and bilayer membranes. Surface pressure/molecular area isotherms of D-erythro-N-16:0-sphingomyelin (16:0-SM) and D-erythro-N-16:0-dihydrosphingomyelin (16:0-DHSM) show very similar packing properties, except that the expanded-to-condensed phase transition (crystallization) occurs at a lower surface pressure for 16:0-DHSM. The measured surface potential was generally about 100 mV less for 16:0-DHSM monolayers compared to 16:0-SM monolayers. The condensed domains (crystals) that formed in 16:0-SM monolayers as a function of compression displayed star-shaped morphology when viewed under an epifluorescence microscope. 16:0-DHSM monolayers did not form similar crystals upon compression. 16:0-DHSM was degraded much faster by sphingomyelinase from Staphylococcus aureus than 16:0-SM (10-fold difference in enzyme activity needed for comparable hydrolytic rate). Cholesterol desorption from 16:0-DHSM to cyclodextrin was slightly slower (approximately 20%) than the rate measured from 16:0-SM monolayers (at 60 mol % cholesterol). The bilayer melting temperature of 16:0-DHSM was 47.7 degrees C (DeltaH 8.3 kcal/mol) whereas it was 41.2 degrees C for 16:0-SM (DeltaH 8.1 kcal/mol). Cholesterol/16:0-DHSM bilayers (15 mol % sterol) had more condensed domains than comparable 16:0-SM bilayers, as evidenced from the quenching resistance of DPH in DHSM membranes. We conclude that cholesterol interacts more favorably with 16:0-DHSM and that the membranes are more condensed than comparable 16:0-SM-containing membranes.
Kuikka
M
M
Department of Biochemistry and Pharmacy, Abo Akademi University, FIN 20521 Turku, Finland.
Ramstedt
B
B
Ohvo-Rekilä
H
H
Tuuf
J
J
Slotte
J P
JP
D016880:Anisotropy; D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry; D003505:Cyclodextrins / Q000737:chemistry; D006868:Hydrolysis; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008856:Microscopy, Fluorescence; D008956:Models, Chemical; D017434:Protein Structure, Tertiary; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
D003505:Cyclodextrins; D008051:Lipid Bilayers; D008081:Liposomes; D013109:Sphingomyelins; D002784:Cholesterol; D013108:Sphingomyelin Phosphodiesterase