title: Solubilization of sphingomyelin vesicles by addition of a bile salt.
abstract: The interactions of the bile salt sodium taurocholate (TC) in 50 mM Trizma-HCl buffer and 150 mM NaCl (pH 9) at 37 degrees C with membranes composed of sphingomyelin (SM) were studied by dynamic light scattering, cryogenic transmission electron microscopy (cryo-TEM) and turbidity measurements. Small unilamellar SM vesicles were prepared by extrusion. Below the CMC of TC, taurocholate addition leads to vesicle growth due to incorporation of the taurocholate molecules into the vesicle bilayer. At around half the CMC of the bile salt, the SM vesicles are transformed into SM/TC mixed worm-like micelles, which are visualized by cryo-TEM for the first time. Further increase in the taurocholate concentration leads to the rupture of these structures into small spherical micelles. Interestingly, large non-spherical micelles were also identified for pure taurocholate solutions. Similar threadlike structures have been reported earlier for the bile salt sodium taurodeoxycholate [Rich, A., Blow, D., 1958. Nature 182, 1777; Blow, D.M., Rich, A., 1960. J. Am. Chem. Soc. 82, 3566-3571; Galantini, L., Giglio, E., La Mesa, C., Viorel-Pavel, N., Punzo, F., 2002. Langmuir 18, 2812] and for mixtures of taurocholate and phosphatidylcholate [Ulmius, J., Lindblom, G., Wennerström, H., Johansson, L.B.-A., Fontel, K., Söderman, O., Ardvisson, G., 1982. Biochemistry 21, 1553; Hjelm, R.P., Thiyagarajan, P., Alkan-Onyuksel, H., 1992. J. Phys. Chem. 96, 8653] as determined by various scattering methods.
authors.affiliation: Biomedical Technology Laboratory, Health and Society, Malmö University, Malmö, Sweden. marite-cardenas.gomez@hs.mah.se
authors.forename: Marité
authors.initials: M
authors.lastname: Cárdenas
authors.forename: Karin
authors.initials: K
authors.lastname: Schillén
authors.forename: Viveka
authors.initials: V
authors.lastname: Alfredsson
authors.forename: Rui-Dong
authors.initials: RD
authors.lastname: Duan
authors.forename: Lena
authors.initials: L
authors.lastname: Nyberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Arnebrant
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D012995:Solubility; D013109:Sphingomyelins / Q000737:chemistry*; D013656:Taurocholic Acid / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008823:Micelles; D013109:Sphingomyelins; D013656:Taurocholic Acid