(794i) Nanoscale Patterning of Membrane-Bound Proteins Formed Through Curvature-Induced Partitioning of Phase-Specific Receptor Lipids
AIChE Annual Meeting
Friday, November 8, 2013 - 10:30am to 10:45am
Lipid mixtures self-assemble to form planar bilayers containing coexisting lipid phases in many compositional regimes. Coexisting lipid phases each have distinct compositions that can selectively partition optically active dyes, ligands, and membrane proteins. Therefore, precise arrangements of these phases in continuous lipid bilayers could be used to create displays of proteins, DNA strands, optically, chemically, or electrically active molecules, or nanoparticles. Curvature-based sorting of functionalized lipids that comprise or partition into specific lipid phases could serve as a way of templating active molecules. A variety of methods have been developed to attach functional molecules to lipid headgroups. These include covalent bonding and linkers such as single-stranded DNA, biotin, and glycan-phosphatidyl inositol. Lipid headgroups can also be functionalized with a metal chelate group such as iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA). These chelate groups coordinate to divalent transition-metal ions such as Cu2+, Ni2+, and Zn2+ and sequester proteins rich with histidine moieties. This work describes a technique for forming high-density arrays and patterns of membrane-bound proteins through binding to a curvature-organized compositional pattern of metal-chelating lipids (Cu2+-DOIDA or Cu2+-DSIDA). In this bottom-up approach, the underlying support is a poly(methyl methacrilate) (PMMA) e-beam formed, square lattice pattern of hemispheres. This curvature pattern sorts Cu2+-DOIDA to the 200 nm hemispherical lattice sites of a 600 nm ´ 600 nm unit cell in Ld - Lo phase separated lipid multibilayers. Binding of histidine-tagged green fluorescent protein (His-GFP) creates a high density array of His-GFP-bound pixels localized to the square lattice sites. In comparison, the negative pixel pattern is created by sorting Cu2+-DSIDA in Ld - Lb phase separated lipid multibilayers to the flat grid between the lattice sites followed by binding to His-GFP. Lattice defects in the His-GFP pattern lead to interesting features such as pattern circularity. We also observe defect-free arrays of His-GFP that demonstrate perfect arrays can be formed by this method suggesting the possibility of using this approach for the localization of various active molecules to form protein, DNA, or optically active molecular arrays.