The perturbation of bilayer properties upon insertion of a single
fullerene molecule was calculated in bilayers of two sizes using
biased molecular dynamics (MD) simulations, in which
fullerene was restrained at different positions along the bilayer
normal. Despite the large size of fullerene, perturbation of the
bilayer structure is relatively small; bilayer thickness, area per
lipid and lipid order parameters change only slightly upon
fullerene insertion (Fig. 3). The deformations are largest when
fullerene is found between 1.5 and 2.9 nm from the centre of
the bilayer. However, even in the smallest bilayer, the area
decreases by less than 2% during fullerene permeation. The
increase in bilayer thickness and in the ordering of the lipid
tails are also minor. These structural changes can be explained
by the appearance of lipid protrusions when fullerene is
inserted in the head group and carbonyl regions. As the lipids
close to fullerene protrude towards the water phase, their tails
stretch and become more ordered. This, in turn, reduces the
area and increases the thickness of the membrane. Structura