Biomedical Engineering Reference
In-Depth Information
brane components and to events that occur at the interface or with-
in the bilayer. For example, biomembranes provide the environ-
mental matrix for proteins that specifically transport certain ions
and other molecules, for receptor proteins and for signal transduc-
tion molecules. The lipid and protein portions of biomembranes
are also sensitive to the presence of lipophilic perturbants. Anaes-
thetics, for example, readily partition into lipid membranes, alter-
ing their electrical and permeability characteristics, thus providing
an indicator for these agents. The various responses observed in
biomembranes are concentration-dependent, usually very rapid and
reversible, and frequently voltage-dependent.
II. THE BIOMIMETIC MEMBRANES:
SCOPE AND REQUIREMENTS
In view of the complexity and diversity of the functions performed
by the different proteins embedded in a biomembrane (the integral
proteins), it has been found convenient to incorporate single inte-
gral proteins or smaller lipophilic biomolecules into experimental
models of biological membranes, so as to isolate and investigate
their functions. This serves to reduce complex membrane process-
es to well-defined interactions between selected proteins, lipids
and ligands. There is great potential for application of experi-
mental models of biomembranes (the so-called biomimetic mem-
branes) for the elucidation of structure-function relationships of
many biologically important membrane proteins. These proteins
are the key factors in cell metabolism, e.g., in cell-cell interactions,
signal transduction, and transport of ions and nutrients. Thanks to
this important function, membrane proteins are a preferred target
for pharmaceuticals, with about 60% of consumed drugs address-
ing them. Biomimetic membranes are also useful for the investiga-
tion of phase stability (e.g., lipid-lipid phase separation, lipid raft
formation, lateral diffusion), protein-membrane interactions (e.g.,
receptor clustering and co-localization), and membrane-membrane
processes such as fusion, electroporation and intercellular recogni-
tions. They are also relevant to the design of membrane-based bio-
sensors and devices, and to analytical platforms for assaying
membrane-based processes.
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