Protein insertion and patterning of PEG bearing langmuir monolayers.

Protein adsorption to multicomponent lipid monolayers is presented as a means of inducing protein-specific binding pockets or imprints in membranes. Adsorption of the acidic protein ferritin to Langmuir monolayers of cationic dioctadecyldimethylammonium bromide (DOMA), nonionic methyl stearate (SME), and poly(ethylene glycol) (PEG) bearing phospholipids is investigated as a model system. The number, size, and distribution of protein binding pockets (domains of SME and DOMA in a PEG matrix) are defined by controlling the molar ratios, miscibility, and lateral mobility of the lipids.

Electrostatic force microscopy analysis of lipid miscibility in two-component monolayers.

Electrostatic force microscopy (EFM) was used to assess lipid miscibility and phase behavior in two-component Langmuir-Blodgett (LB) monolayers composed of cationic dioctadecyldimethylammonium bromide (DOMA) and nonionic methyl stearate (SME) lipids. The surface potential measurements were calibrated by applying known bias voltages to the sample during several line scans, thus creating surface potential "scale bars" on the images from which it was determined that circular domains were 50 mV more positive than the surrounding phase. As the spatially averaged surface potential of DOMA was over 400 mV more positive than that of SME, this 50-mV surface potential difference is too low to correspond to lipid phase separation (immiscibility) in the two-component film.