Electrochemical investigation of melittin reconstituted into a mercury-supported lipid bilayer.
The channel-forming peptide melittin was incorporated into a biomimetic membrane consisting of a mercury electrode coated with a thiolipid monolayer, with a lipid monolayer self-assembled on top of it. The thiolipid consisted of a hydrophilic tetraethyleneoxy chain terminated at one end with a disulfide group, for anchoring to the mercury surface, and covalently linked at the other end to two diphytanyl chains, which formed a lipid bilayer with the overhanging lipid monolayer. The conductance of the lipid bilayer in contact with aqueous 0.1 M KCl was measured by electrochemical impedance spectroscopy over a frequency range from 1 x 10(-2) to 1 x 10(5) Hz and a potential range of 0.7 V for different compositions of the outer lipid monolayer. The conductance increases abruptly above the background level at sufficiently negative applied potentials, attaining a maximum value that increases with the composition of the outer monolayer in the order PC/chol (60:40) < PC < PC/SM/chol (59:15:26) < PS, with PC = phosphatidylcholine, chol = cholesterol, SM = sphingomyelin, and PS = phosphatidylserine. The higher the maximum conductance, the less negative the applied potential at which it is attained. This behavior is also discussed using a model of the electrified interphase.
Becucci
Lucia
L
Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy.
León
Reyes Romero
RR
Moncelli
Maria Rosa
MR
Rovero
Paolo
P
Guidelli
Rolando
R
D004563:Electrochemistry; D004566:Electrodes; D008051:Lipid Bilayers / Q000737:chemistry*; D008555:Melitten / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D013499:Surface Properties
D008051:Lipid Bilayers; D008555:Melitten; D008628:Mercury