Enhanced Brownian Ratchet
Molecular Separation Using
a Self-Spreading Lipid Bilayer
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Abstract
A new approach is proposed for two-dimensional molecular
separation
based on the Brownian ratchet mechanism by use of a self-spreading
lipid bilayer as both a molecular transport and separation medium.
In addition to conventional diffusivity-dependence on the ratchet
separation efficiency, the difference in the intermolecular interactions
between the target molecules and the lipid bilayer is also incorporated
as a new separation factor in the present self-spreading ratchet system.
Spreading at the gap between two ratchet obstacles causes a local
change in the lipid density at the gap. This effect produces an additional
opportunity for a molecule to be deflected at the ratchet obstacle
and thus causes an additional angle shift. This enables the separation
of molecules with the same diffusivity but with different intermolecular
interaction between the target molecule and surrounding lipid molecules.
Here we demonstrate this aspect by using cholera toxin subunit B (CTB)–ganglioside
GM1 (GM1) complexes with different configurations. The present results
will unlock a new strategy for two-dimensional molecular manipulation
with ultrasmall devices