title: The effect of the hydrophilic spacer length on the functionality of a mercury-supported tethered bilayer lipid membrane.
abstract: A biomimetic membrane consisting of a thiolipid monolayer tethered to a mercury electrode, with a dioleoylphosphatidylcholine (DOPC) monolayer on top of it, was fabricated. The thiolipid, referred to as DPOL, consisted of an octaethyleneoxy (OEO) chain terminated at one end with a lipoic acid residue and covalently linked at the other end to two phytanyl chains. The functionality of this biomimetic membrane, referred to as a tethered bilayer lipid membrane (tBLM), was tested by incorporating gramicidin and alamethicin and verifying their ion channel activity. Advantages and drawbacks with respect to a tBLM using a thiolipid, referred to as DPTL, with a tetraethyleneoxy (TEO) chain were examined by using electrochemical impedance spectroscopy, potential-step chronocoulometry and cyclic voltammetry. The maximum charge surface density of potassium ions stored in the OEO spacer amounts to 70μCcm(-2), as compared to a charge surface density of 45μCcm(-2) in the TEO spacer. The lipid bilayer moiety of the DPOL/DOPC tBLM is somewhat leakier than that of the DPTL/DOPC tBLM at potentials negative of about -0.65V vs. the saturated calomel electrode. The estimated value of the surface dipole potential of the OEO spacer amounts to -0.180V and is, therefore, smaller than that, -0.230V, of the TEO spacer.
authors.affiliation: Institute for the Chemistry of Organometallic Compounds (ICCOM) of the National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy. Electronic address: lucia.becucci@unifi.it.
authors.forename: Lucia
authors.initials: L
authors.lastname: Becucci
authors.affiliation: Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Faragher
authors.affiliation: Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Adrian
authors.initials: A
authors.lastname: Schwan
mesh_terms: D040761:Biomimetic Materials; D002104:Cadmium / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry; D058266:Dielectric Spectroscopy; D004563:Electrochemistry / Q000379:methods; D006096:Gramicidin / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D013329:Structure-Activity Relationship; D015032:Zinc / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D002104:Cadmium; D006096:Gramicidin; C017251:1,2-oleoylphosphatidylcholine; D008628:Mercury; D015032:Zinc
keywords: Alamethicin; Dioleoylphosphatidylcholine; Electrochemical impedance spectroscopy; Gramicidin; Tethered bilayer lipid membrane