Pressure-temperature phase behavior of mixtures of natural sphingomyelin and ceramide extracts.
Ceramides are a group of sphingolipids that act as highly important signaling molecules in a variety of cellular processes including differentiation and apoptosis. The predominant in vivo synthetic pathway for ceramide formation is via sphingomyelinase catalyzed hydrolysis of sphingomyelin. The biochemistry of this essential pathway has been studied in detail; however, there is currently a lack of information on the structural behavior of sphingomyelin- and ceramide-rich model membrane systems, which is essential for developing a bottom-up understanding of ceramide signaling and platform formation. We have studied the lyotropic phase behavior of sphingomyelin-ceramide mixtures in excess water as a function of temperature (30-70 °C) and pressure (1-200 MPa) by small- and wide-angle X-ray scattering. At low ceramide concentrations the mixtures form the ripple gel phase (P(β)') below the gel transition temperature for sphingomyelin, and this observation has been confirmed by atomic force microscopy. Formation of the ripple gel phase can also be induced at higher temperatures via the application of hydrostatic pressure. At high ceramide concentration an inverse hexagonal phase (HII) is formed coexisting with a cubic phase.
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Hanna M G
HM
Barriga
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Edward S
ES
Parsons
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Nicola L C
NL
McCarthy
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Oscar
O
Ces
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
John M
JM
Seddon
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Robert V
RV
Law
Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom.
Nicholas J
NJ
Brooks
D000818:Animals; D002518:Ceramides / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature
D002518:Ceramides; D013109:Sphingomyelins