title: Formation of nanoparticle arrays on S-layer protein lattices.
abstract: Crystalline bacterial cell surface layers (S-layers) composed of identical protein units have been used as binding templates for well-organized arrangements of nanoparticles. Isolated S-layer proteins were recrystallized into monomolecular arrays on solid substrates (such as silicon wafers and SiO2-coated grids) and in suspension forming so-called self-assembly products. These S-layer assemblies were studied by atomic force microscopy and transmission electron microscopy (TEM). The orientation of the S-layer lattice, exhibiting anisotropic surface properties, on the solid surface and on the self-assembly products, was compared with the orientation on the bacterial cell. On both bacterial cells and SiO2 surfaces the outer face of the S-layer protein was exposed. On the self-assembly products occasionally the inner face was also visible. Metal- and semiconductor nanoparticles 2 to 10 nm in mean diameter were covalently or electrostatically bound to the solid-supported S-layers and self-assembly products. TEM studies reveal that upon activation of carboxyl groups in the S-layer lattice with 1-ethyl-3,3'(dimethylaminopropyl)carbodiimide (EDC), a close-packed monolayer of 4-nm amino-functionalized CdSe nanoparticles could be covalently established on the S-layer lattice. Because of electrostatic interactions, anionic citrate-stabilized Au nanoparticles (5 nm in diameter) formed a superlattice at those sites where the inner face of the S-layer lattice was exposed. In contrast, cationic semiconductor nanoparticles (such as amino-functionalized CdSe particles) formed arrays on the outer face of the solid-supported S-layer lattices.
authors.affiliation: Center for Ultrastructure Research, Ludwig Bolzmann Institute for Molecular Nanotechnology, Universität für Bodenkultur Vienna, A-1180 Vienna, Austria.
authors.forename: Erika
authors.initials: E
authors.lastname: Györvary
authors.forename: Andrea
authors.initials: A
authors.lastname: Schroedter
authors.forename: Dimitri V
authors.initials: DV
authors.lastname: Talapin
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
authors.forename: Dietmar
authors.initials: D
authors.lastname: Pum
authors.forename: Uwe B
authors.initials: UB
authors.lastname: Sleytr
mesh_terms: D000327:Adsorption; D019187:Cadmium Compounds / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis / Q000737:chemistry; D003460:Crystallization / Q000295:instrumentation / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D011485:Protein Binding; D018036:Selenium Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D019187:Cadmium Compounds; D020099:Coated Materials, Biocompatible; D046911:Macromolecular Substances; D018036:Selenium Compounds; D006046:Gold; C058667:cadmium selenide