TY - JOUR

T1 - Phase behavior and lipid-membrane structure of phospholipid- glycosphingolipid liposomes and the thermal unfolding of insulin

AU - Pedersen, Tina B.

AU - Frokjaer, Sven

AU - Mouritsen, Ole G.

AU - Jørgensen, Kent

PY - 1999/1/1

Y1 - 1999/1/1

N2 - The thermodynamic phase behavior and lipid-membrane structure of fully hydrated uni- and multilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) surface-modified by a glycosphingolipid, sulfogalactosylceramide (sulfatide), have been investigated by means of differential scanning calorimetry and fluorescence polarization spectroscopy. The calorimetric and spectroscopic scans of the two-component liposomes demonstrate a distinct influence of increasing amounts of sulfatide on the lipid-membrane thermodynamics. This is manifested as a broad gel-fluid phase-coexistence region and a low-temperature two- phase region composed of highly ordered lipids. In addition, the pre- transition is abolished for small concentrations of sulfatide. A well- defined heat capacity peak, reflecting a thermotropic chain melting transition is observed for liposomes composed of pure sulfatide. On basis of the calorimetric and spectroscopic data a phase diagram has been established in the full temperature and composition plane. Dynamic light scattering measurements of liposome sizes reveal that the incorporation of sulfatide into the DPPC membrane matrix leads to a stabilization of the characteristic size of the extruded liposomes. Furthermore, incubation with insulin does not affect the liposome size and the aggregational behavior of the two-component sulfatide-DPPC liposomes. In accordance with this, the heat capacity curves demonstrate an insignificant influence on both the lipid membrane phase behavior and the thermal unfolding characteristics of insulin.

AB - The thermodynamic phase behavior and lipid-membrane structure of fully hydrated uni- and multilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) surface-modified by a glycosphingolipid, sulfogalactosylceramide (sulfatide), have been investigated by means of differential scanning calorimetry and fluorescence polarization spectroscopy. The calorimetric and spectroscopic scans of the two-component liposomes demonstrate a distinct influence of increasing amounts of sulfatide on the lipid-membrane thermodynamics. This is manifested as a broad gel-fluid phase-coexistence region and a low-temperature two- phase region composed of highly ordered lipids. In addition, the pre- transition is abolished for small concentrations of sulfatide. A well- defined heat capacity peak, reflecting a thermotropic chain melting transition is observed for liposomes composed of pure sulfatide. On basis of the calorimetric and spectroscopic data a phase diagram has been established in the full temperature and composition plane. Dynamic light scattering measurements of liposome sizes reveal that the incorporation of sulfatide into the DPPC membrane matrix leads to a stabilization of the characteristic size of the extruded liposomes. Furthermore, incubation with insulin does not affect the liposome size and the aggregational behavior of the two-component sulfatide-DPPC liposomes. In accordance with this, the heat capacity curves demonstrate an insignificant influence on both the lipid membrane phase behavior and the thermal unfolding characteristics of insulin.

KW - Glycosphingolipid

KW - Insulin

KW - Phase behavior liposome stabilization

KW - Phospholipid

KW - Sulfatide

UR - http://www.scopus.com/inward/record.url?scp=0033003033&partnerID=8YFLogxK

U2 - 10.3109/08982109909024789

DO - 10.3109/08982109909024789

M3 - Journal article

AN - SCOPUS:0033003033

VL - 9

SP - 261

EP - 274

JO - Journal of Liposome Research

JF - Journal of Liposome Research

SN - 0898-2104

IS - 2

ER -