title: Channel-forming activity of syringomycin E in two mercury-supported biomimetic membranes.
abstract: The lipodepsipeptide syringomycin E (SR-E) interacts with two mercury-supported biomimetic membranes, which consist of a self-assembled phospholipid monolayer (SAM) and of a tethered bilayer lipid membrane (tBLM) separated from the mercury surface by a hydrophilic tetraethyleneoxy (TEO) spacer that acts as an ionic reservoir. SR-E interacts more rapidly and effectively with a SAM of dioleoylphosphatidylserine (DOPS) than with one of dioleoylphosphatidylcholine (DOPC). The proximal lipid monolayer of the tBLM has no polar head region, being linked to the TEO spacer via an ether bond, while the distal monolayer consists of either a DOPC or a DOPS leaflet. The ion flow into or out of the spacer through the lipid bilayer moiety of the tBLM was monitored by potential step chronocoulometry and cyclic voltammetry. With the distal monolayer bathed by aqueous 0.1M KCl and 0.8μM SR-E, an ion flow in two stages was monitored with DOPC at pH3 and 5.4 and with DOPS at pH3, while a single stage was observed with DOPS at pH5.4. This behavior was compared with that already described at conventional bilayer lipid membranes. The sigmoidal shape of the chronocoulometric charge transients points to an aggregation of SR-E monomers forming an ion channel via a mechanism of nucleation and growth. The ion flow is mainly determined by potassium ions, and is inhibited by calcium ions. The contribution to the transmembrane potential from the distal leaflet depends more on the nature of the lipid than that of the ion channel.
authors.affiliation: Department of Chemistry, Florence University, via della Lastruccia 3, 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, Florence University, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
authors.forename: Vania
authors.initials: V
authors.lastname: Tramonti
authors.affiliation: Department of Agricultural and Food Science, University of Naples "Federico II", 80055 Portici, Italy; School of Science, Engineering & Technology, Division of Food & Life Sciences, Abertay University, Kydd Building, Dundee, DD1 1HG, UK.
authors.forename: Alberto
authors.initials: A
authors.lastname: Fiore
authors.affiliation: Department of Agricultural and Food Science, University of Naples "Federico II", 80055 Portici, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Fogliano
authors.affiliation: Proteomics & Mass Spectrometry Laboratory, ISPAAM-National Research Council, 80147 Naples, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.affiliation: Florence University, Italy.
authors.forename: Rolando
authors.initials: R
authors.lastname: Guidelli
mesh_terms: D001427:Bacterial Toxins / Q000494:pharmacology; D032701:Biomimetics; D002462:Cell Membrane / Q000737:chemistry*; D004563:Electrochemistry; D007473:Ion Channels / Q000187:drug effects*; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials / Q000187:drug effects; D008628:Mercury / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000737:chemistry*; D010718:Phosphatidylserines / Q000737:chemistry*
chemical_list: D001427:Bacterial Toxins; D007473:Ion Channels; D008051:Lipid Bilayers; D010456:Peptides, Cyclic; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; C105246:syringomycin E; C042511:1,2-dioleoylphosphatidylserine; C017251:1,2-oleoylphosphatidylcholine; D008628:Mercury
keywords: Cyclic voltammetry; Lipodepsipeptides; Potential step chronocoulometry; Self-assembled monolayers; Tethered bilayer lipid membranes