title: Formation of an ordered phase by ceramides and diacylglycerols in a fluid phosphatidylcholine bilayer--Correlation with structure and hydrogen bonding capacity.
abstract: Ceramides and diacylglycerols are lipids with a large hydrophobic part (acyl chains and long-chain base) whereas their polar function (hydroxyl group) is small. They need colipids with large head groups to coexist in bilayer membranes. In this study, we have determined how saturated and unsaturated ceramides and acyl-chain matched diacylglycerols form ordered domains in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers as a function of bilayer concentration. The formation of ordered domains was determined from lifetime analysis of trans-parinaric acid. Ceramides formed ordered domains with equal average tPA lifetime at lower bilayer concentration when compared to acyl-chain matched diacylglycerols. This was true for both saturated (16:0) and mono-unsaturated (18:1) species. This finding suggested that hydrogen bonding among ceramides contributed to their more efficient ordered phase formation, since diacylglycerols do not form similar hydrogen bonding networks. The role of hydrogen bonding in ordered domain formation was further verified by using palmitoyl ceramide analogs with 2N and 3OH methylated long-chain bases. These analogs do not form hydrogen bonds from the 2NH or the 3OH, respectively. While methylation of the 3OH did not affect ordered phase formation compared to native palmitoyl ceramide, 2NH methylation markedly attenuated ceramide ordered phase formation. We conclude that in addition to acyl chain length, saturation, molecular order, and lack of large head group, also hydrogen bonding involving the 2NH is crucial for efficient formation of ceramide-rich domains in fluid phosphatidylcholine bilayers.
authors.affiliation: Biochemistry, Faculty of Science Engineering, Åbo Akademi University, 20520 Turku, Finland.
authors.forename: Peik
authors.initials: P
authors.lastname: Ekman
authors.affiliation: Biochemistry, Faculty of Science Engineering, Åbo Akademi University, 20520 Turku, Finland.
authors.forename: Terhi
authors.initials: T
authors.lastname: Maula
authors.affiliation: School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda City, Hyogo 669-1337, Japan.
authors.forename: Shou
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda City, Hyogo 669-1337, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Biochemistry, Faculty of Science Engineering, Åbo Akademi University, 20520 Turku, Finland.
authors.forename: Thomas K M
authors.initials: TK
authors.lastname: Nyholm
authors.affiliation: School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda City, Hyogo 669-1337, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Katsumura
authors.affiliation: Biochemistry, Faculty of Science Engineering, Åbo Akademi University, 20520 Turku, Finland. Electronic address: jpslotte@abo.fi.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D002518:Ceramides / Q000737:chemistry*; D004075:Diglycerides / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D012996:Solutions; D013223:Statistics as Topic
chemical_list: D002518:Ceramides; D004075:Diglycerides; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D012996:Solutions; D006859:Hydrogen
keywords: Fluorescence life time analysis; Hydrogen bonding; Phase separation; Trans-parinaric acid