The self-assembled monolayers (SAMs) of the new lipidic anchor molecule, Z 20-(Z-octadec-9-enyloxy)-3,6,9,12,15,18,22-heptaoxatetracont-31-ene-1-thiol (HC18), and mixed HC18/-mercaptoethanol (ME) SAMs were studied by spectroscopic ellipsometry, contact angle measurements, reflection adsorption infrared spectroscopy (RAIRS) , electrochemical impedance spectroscopy (EIS), and evaluated in tethered bilayer lipid membranes (tBLMs). Our data indicate that HC18, containing a double bond in the alkyl segments, forms highly disordered SAMs up to anchor/ME molar fraction ratios of 80 %/20 % and result in tBLMs that exhibit higher lipid diffusion coefficients, relative to previous anchor compounds with saturated alkyl chains, as determined by fluorescence correlation spectroscopy. EIS data shows the HC18 tBLMs, completed by RSE or vesicle fusion, form more easily, exhibit excellent electrical insulating properties, indicating low defect densities, and readily incorporate the pore forming toxin, -hemolysin. Neutron reflectivity measurements on HC18 tBLMs confirm the formation of complete tBLMs at very low tether compositions and high ionic lipid compositions [40 % 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG)]. Our data indicates HC18 results in tBLMs with improved physical properties for incorporation of integral membrane proteins (IMPs) and that the 80 % HC18 tBLMs appear to be optimal for practical applications such as biosensors where high electrical insulation and IMP/peptide reconstitution is imperative.
Citation: Berichte Der Bunsen-Gesellschaft-Physical Chemistry Chemical Physics
Pub Type: Journals
tethered bilayer lipid membranes, self-assembled monolayers, electrochemical impedance spectroscopy, neutron reflectivity