Generic phase behavior of branched-chain phospholipid monolayers.
Monolayers of chemically modified triple-chain phospholipids have been investigated at the air/water interface using pressure-area isotherms. The condensed phases of the lipids were characterized by grazing incidence X-ray diffraction (GIXD). Increasing chain length corresponds to a temperature effect, which was quantified for different lipids, depending on the head group structure using isotherm (two-dimensional systems) and DSC (three-dimensional systems) measurements. The combination of structure investigations revealed generic phase diagrams, which describe the phase behavior of multiple-chain lipids in two dimensions. For the 1-acyl-2-O-alkyl phospholipids, the generic phase diagram exhibits only L(2d), LS and LE phases while the exchange of the position of the branched acyl and the non-branched alkyl chains at the glycerol backbone leads to a much richer polymorphism (L(2h), L(2d), Ov, LS, S, tau, LE). Here we present the first experimental evidence of the unusual tau phase for multiple-chain lipid monolayers. This phase exhibits an undistorted in-plane lattice despite of tilted chains.
Institute of Biophysics and X-ray research, Schmiedlstrasse 6, 8042 Graz, Austria.
Frank
F
Bringezu
Bodo
B
Dobner
Gerald
G
Brezesinski
D008823:Micelles; D010743:Phospholipids / Q000737:chemistry*; D011312:Pressure; D013329:Structure-Activity Relationship; D013696:Temperature; D013816:Thermodynamics
D008823:Micelles; D010743:Phospholipids