STRUCTURE OF MIXED MULTILAYERS OF PALMITOYLOLEOYLPHOSPHATIDYLCHOLINE AND OLIGO(OXYETHYLENE GLYCOL) MONODODECYL ETHER DETERMINED BY X-RAY AND NEUTRON-DIFFRACTION
G. Klose et al., STRUCTURE OF MIXED MULTILAYERS OF PALMITOYLOLEOYLPHOSPHATIDYLCHOLINE AND OLIGO(OXYETHYLENE GLYCOL) MONODODECYL ETHER DETERMINED BY X-RAY AND NEUTRON-DIFFRACTION, Langmuir, 12(2), 1996, pp. 409-415
The structure of oriented multilayers of the zwitterionic phospholipid
palmitoyloleoylphosphatidylcholine containing nonionic surfactants (o
ligo(oxyethylene glycol) monododecyl ethers, C(12)E(n) with n = 2, 4,
and 6) was studied by X-ray and neutron diffraction. Investigations we
re done at T = 20 degrees C in the lamellar liquid-crystalline phase w
ith surfactant/lipid molar ratios R(A/L) = 0.5 and 1 and hydration lev
els corresponding to 85 and 97% relative humidity. The transbilayer di
stribution of the surfactant was determined by neutron diffraction usi
ng selectively deuterated C(12)E(n). The incorporation of surfactant c
auses a decrease of the repeat distance and of the thickness of the hy
drocarbon core of the membrane. The effect increases with the number o
f oxyethylene units and with the concentration of the surfactant as we
ll as with the relative humidity. The alpha-methylene group of the sur
factants is anchored near the boundary of the hydrophobic core. The ox
yethylene moieties are mainly located in the polar membrane/water inte
rface region. The impact of molecular disorder on the diffraction data
is discussed.