title: The Influence of Hydrogen Bonding on Sphingomyelin/Colipid Interactions in Bilayer Membranes.
abstract: The phospholipid acyl chain composition and order, the hydrogen bonding, and properties of the phospholipid headgroup all influence cholesterol/phospholipid interactions in hydrated bilayers. In this study, we examined the influence of hydrogen bonding on sphingomyelin (SM) colipid interactions in fluid uni- and multilamellar vesicles. We have compared the properties of oleoyl or palmitoyl SM with comparable dihydro-SMs, because the hydrogen bonding properties of SM and dihydro-SM differ. The association of cholestatrienol, a fluorescent cholesterol analog, with oleoyl sphingomyelin (OSM) was significantly stronger than its association with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, in bilayers with equal acyl chain order. The association of cholestatrienol with dihydro-OSM, which lacks a trans double bond in the sphingoid base, was even stronger than the association with OSM, suggesting an important role for hydrogen bonding in stabilizing sterol/SM interactions. Furthermore, with saturated SM in the presence of 15 mol % cholesterol, cholesterol association with fluid dihydro-palmitoyl SM bilayers was stronger than seen with palmitoyl SM under similar conditions. The different hydrogen bonding properties in OSM and dihydro-OSM bilayers also influenced the segregation of palmitoyl ceramide and dipalmitoylglycerol into an ordered phase. The ordered, palmitoyl ceramide-rich phase started to form above 2 mol % in the dihydro-OSM bilayers but only above 6 mol % in the OSM bilayers. The lateral segregation of dipalmitoylglycerol was also much more pronounced in dihydro-OSM bilayers than in OSM bilayers. The results show that hydrogen bonding is important for sterol/SM and ceramide/SM interactions, as well as for the lateral segregation of a diglyceride. A possible molecular explanation for the different hydrogen bonding in SM and dihydro-SM bilayers is presented and discussed.
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Md Abdullah
authors.initials: MA
authors.lastname: Al Sazzad
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Niklas Z
authors.initials: NZ
authors.lastname: Jäntti
authors.affiliation: Computational Bioscience Laboratory, Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Jyvaskyla, Finland.
authors.forename: Olli T
authors.initials: OT
authors.lastname: Pentikäinen
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland. Electronic address: jpslotte@abo.fi.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D002518:Ceramides / Q000737:chemistry; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D009829:Oleic Acids / Q000737:chemistry; D010169:Palmitic Acids / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry*
chemical_list: D002518:Ceramides; D008051:Lipid Bilayers; D009829:Oleic Acids; D010169:Palmitic Acids; D013109:Sphingomyelins