Biophys J, May 2000, p. 2459-2469, Vol. 78, No. 5

Dimyristoylphosphatidylcholine/C16:0-Ceramide Binary Liposomes Studied by Differential Scanning Calorimetry and Wide- and Small-Angle X-Ray Scattering

Juha M. Holopainen,^* Jesper Lemmich, Frank Richter,^§¶ Ole G. Mouritsen, Gert Rapp,^§ and Paavo K. J. Kinnunen^*

 ^*Helsinki Biophysics and Biomembrane Group, Department of Medical Chemistry, Institute of Biomedicine, University of Helsinki, Helsinki, Finland;  Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby, Denmark;  Condensed Matter Physics and Chemistry Department, Risø, National Laboratory, DK-4000, Roskilde, Denmark;  ^§European Molecular Biology Laboratory, Hamburg Outstation at DESY, D-22603 Hamburg, Germany; and  ^¶Department of Physics, E22 Biophysics, TU Munich, 85748 Garching, Germany

Ceramide has recently been established as a central messenger in the signaling cascades controlling cell behavior. Physicochemical studies have revealed a strong tendency of this lipid toward phase separation in mixtures with phosphatidylcholines. The thermal phase behavior and structure of fully hydrated binary membranes composed of dimyristoylphosphatidylcholine (DMPC) and N-palmitoyl-ceramide (C16:0-ceramide, up to a mole fraction X_cer = 0.35) were resolved in further detail by high-sensitivity differential scanning calorimetry (DSC) and x-ray diffraction. Both methods reveal very strong hysteresis in the thermal phase behavior of ceramide-containing membranes. A partial phase diagram was constructed based on results from a combination of these two methods. DSC heating scans show that with increased X_cer the pretransition temperature T_p first increases, whereafter at X_cer > 0.06 it can no longer be resolved. The main transition enthalpy H remains practically unaltered while its width increases significantly, and the upper phase boundary temperature of the mixture shifts to ~63°C at X_cer = 0.30. Upon cooling, profound phase separation is evident, and for all of the studied compositions there is an endotherm in the region close to the T_m for DMPC. At X_cer  0.03 a second endotherm is evident at higher temperatures, starting at 32.1°C and reaching 54.6°C at X_cer = 0.30. X-ray small-angle reflection heating scans reveal a lamellar phase within the temperature range of 15-60°C, regardless of composition. The pretransition is observed up to X_cer < 0.18, together with an increase in T_p. In the gel phase the lamellar repeat distance d increases from ~61 Å at X_cer = 0.03, to 67 Å at X_cer = 0.35. In the fluid phase increasing X_cer from 0.06 to 0.35 augments d from 61 Å to 64 Å. An L_'/L (ripple/fluid) phase coexistence region is observed at high temperatures (from 31 to 56.5°C) when X_cer > 0.03. With cooling from temperatures above 50°C we observe a slow increase in d as the coexistence region is entered. A sudden solidification into a metastable, modulated gel phase with high d values is observed for all compositions at ~24°C. The anomalous swelling for up to X_cer = 0.30 in the transition region is interpreted as an indication of bilayer softening and thermally reduced bending rigidity.

Biophys J, May 2000, p. 2459-2469, Vol. 78, No. 5
© 2000 by the Biophysical Society   0006-3495/00/05/2459/11  $2.00

This article has been cited by other articles:

				W. L. Holland and S. A. Summers Sphingolipids, Insulin Resistance, and Metabolic Disease: New Insights from in Vivo Manipulation of Sphingolipid Metabolism Endocr. Rev., June 1, 2008; 29(4): 381 - 402. [Abstract] [Full Text] [PDF]

				E. Falck, J. T. Hautala, M. Karttunen, P. K. J. Kinnunen, M. Patra, H. Saaren-Seppala, I. Vattulainen, S. K. Wiedmer, and J. M. Holopainen Interaction of Fusidic Acid with Lipid Membranes: Implications to the Mechanism of Antibiotic Activity Biophys. J., September 1, 2006; 91(5): 1787 - 1799. [Abstract] [Full Text] [PDF]

				M. Fidorra, L. Duelund, C. Leidy, A. C. Simonsen, and L.A. Bagatolli Absence of Fluid-Ordered/Fluid-Disordered Phase Coexistence in Ceramide/POPC Mixtures Containing Cholesterol Biophys. J., June 15, 2006; 90(12): 4437 - 4451. [Abstract] [Full Text] [PDF]

				J. A. Rotolo, J. Zhang, M. Donepudi, H. Lee, Z. Fuks, and R. Kolesnick Caspase-dependent and -independent Activation of Acid Sphingomyelinase Signaling J. Biol. Chem., July 15, 2005; 280(28): 26425 - 26434. [Abstract] [Full Text] [PDF]

				S. A. Summers and D. H. Nelson A Role for Sphingolipids in Producing the Common Features of Type 2 Diabetes, Metabolic Syndrome X, and Cushing's Syndrome Diabetes, March 1, 2005; 54(3): 591 - 602. [Abstract] [Full Text] [PDF]

				F.-X. Contreras, G. Basanez, A. Alonso, A. Herrmann, and F. M. Goni Asymmetric Addition of Ceramides but not Dihydroceramides Promotes Transbilayer (Flip-Flop) Lipid Motion in Membranes Biophys. J., January 1, 2005; 88(1): 348 - 359. [Abstract] [Full Text] [PDF]

				T. K. M. Nyholm, M. Nylund, and J. P. Slotte A Calorimetric Study of Binary Mixtures of Dihydrosphingomyelin and Sterols, Sphingomyelin, or Phosphatidylcholine Biophys. J., May 1, 2003; 84(5): 3138 - 3146. [Abstract] [Full Text] [PDF]

				T.-Y. Wang and J. R. Silvius Sphingolipid Partitioning into Ordered Domains in Cholesterol-Free and Cholesterol-Containing Lipid Bilayers Biophys. J., January 1, 2003; 84(1): 367 - 378. [Abstract] [Full Text] [PDF]

				Y.-W. Hsueh, R. Giles, N. Kitson, and J. Thewalt The Effect of Ceramide on Phosphatidylcholine Membranes: A Deuterium NMR Study Biophys. J., June 1, 2002; 82(6): 3089 - 3095. [Abstract] [Full Text] [PDF]

				X. Xu, R. Bittman, G. Duportail, D. Heissler, C. Vilcheze, and E. London Effect of the Structure of Natural Sterols and Sphingolipids on the Formation of Ordered Sphingolipid/Sterol Domains (Rafts). COMPARISON OF CHOLESTEROL TO PLANT, FUNGAL, AND DISEASE-ASSOCIATED STEROLS AND COMPARISON OF SPHINGOMYELIN, CEREBROSIDES, AND CERAMIDE J. Biol. Chem., August 31, 2001; 276(36): 33540 - 33546. [Abstract] [Full Text] [PDF]