Biomedical Engineering Reference
In-Depth Information
4
Electrochemistry of Biomimetic
Membranes
Rolando Guidelli and Lucia Becucci
Dept. of Chemistry, Florence University, Via della Lastruccia 3
50019 Sesto Fiorentino, Firenze, Italy
I. INTRODUCTION
Biological membranes are by far the most important electrified
interfaces in living systems. They consist of a bimolecular layer of
lipids (the lipid bilayer) incorporating proteins. Lipid molecules
are
amphiphilic
, i.e., consist of a hydrophobic section (the hydro-
carbon tail) and a hydrophilic section (the polar head). In biologi-
cal membranes the two lipid monolayers are oriented with the hy-
drocarbon tails directed toward each other and the polar heads
turned toward the aqueous solutions that bath the two sides of the
membrane. The resulting lipid bilayer is a matrix that incorporates
different proteins performing a variety of functions. Biomem-
branes form a highly selective barrier between the inside and the
outside of living cells. They are highly insulating to inorganic ions,
and large electrochemical potentialdifferences can be maintained
across them. The permeability and structural properties of biologi-
cal membranes are sensitive to the chemical nature of the mem-
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