1 research outputs found
Modulating the Lateral Tension of Solvent-Free Pore-Spanning Membranes
The plasma membrane of animal cells
is attached to the cytoskeleton,
which significantly contributes to the lateral tension of the membrane.
Lateral membrane tension has been shown to be an important physical
regulator of cellular processes such as cell motility and morphology
as well as exo- and endocytosis. Here, we report on lipid bilayers
spanning highly ordered pore arrays, where we can control the lateral
membrane tension by chemically varying the surface functionalization
of the porous substrate. Surface functionalization was achieved by
a gold coating on top of the pore rims of the hexagonal array of pores
in silicon nitride substrates with pore radii of 600 nm followed by
subsequent incubation with various <i>n</i>-propanolic mixtures
of 6-mercapto-1-hexanol (6MH) and <i>O</i>-cholesteryl <i>N</i>-(8′-mercapto-3′,6′-dioxaoctyl)Âcarbamate
(CPEO3). Pore-spanning membranes composed of 1,2-diphytanoyl-<i>sn</i>-glycero-3-phosphocholine were prepared by spreading giant
unilamellar vesicles on these functionalized porous silicon nitride
substrates. Different mixtures of 6MH and CPEO3 provided self-assembled
monolayers (SAMs) with different compositions as analyzed by contact
angle and PM-IRRAS measurements. Site specific force-indentation experiments
on the pore-spanning membranes attached to the different SAMs revealed
a clear dependence of the amount of CPEO3 in the monolayer on the
lateral membrane tension. While bilayers on pure 6MH monolayers show
an average lateral membrane tension of 1.4 mN m<sup>–1</sup>, a mixed monolayer of CPEO3 and 6MH obtained from a solution with
9.1 mol % CPEO3 exhibits a lateral tension of 5.0 mN m<sup>–1</sup>. From contact angle and PM-IRRAS results, the mole fraction of CPEO3
in solution can be roughly translated into a CPEO3 surface concentration
of 40 mol %. Our results clearly demonstrate that the free energy
difference between the supported and freestanding part of the membrane
depends on the chemical composition of the SAM, which controls the
lateral membrane tension