Chemistry Reference
In-Depth Information
Fig. 1.3
Biomimetic circuits formed using water, oil, lipids and artificial ion pores.
a
The aqueous
droplets form electrical 'solder points' and each droplet is connected to its neighbour via a lipid
bilayer.
b
Different artificial functional ion pores self insert into the lipid bilayers, providing ionic
connectivity in the droplet network
[
16
-
18
]. Here, aqueous droplets are immersed in an external oil phase containing
lipids such that they are covered by lipid monolayers. One can form networks of
such droplets, reminiscent of cellular networks, with the lipid bilayers between the
of these concepts to creating self assembled soft functional devices, with the lipid
bilayer as the fundamental building block.
Another key process of membrane transport, namely, membrane fusion (lower
panel of Fig.
1.2
), by which small vesicles carrying biomolecular cargo fuse with the
plasma membrane to release their contents to either side, is active in processes such as
neural signalling. Membrane fusion is a complex physical process since it involves
the overcoming of a significant energy barrier (
40
K
BT
) for two membranes to
fuse. Therefore, in most biological membrane fusion processes, the energy barrier
is overcome actively by proteins. Particularly, in synaptic communication in the
nervous system, a complex of proteins, known as the SNAREs, coordinate the fusion
process. The proteins act like zippers bringing twomembranes to fusion, with various
influence of the electrostatic interactions due to charged lipid membranes in the
SNARE-mediated fusion process.
In spite of the great advances in the understanding of both natural and artificial
lipid bilayers and their processes, a fundamental limitation still lies in direct imag-
ing of bilayers. Phase contrast microscopy [
21
] has been instrumental in unravelling
∼
