Nanoparticle Ring Structures based on Protein Assemblies
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0901-Ra03-02.1
Nanoparticle Ring Structures based on Protein Assemblies Silke Behrens,1 Wilhelm Habicht,1 Kerstin Wagner,2 and Eberhard Unger2 1
Institut für Technische Chemie, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany. 2 Institut für Molekulare Biotechnologie, Beutenbergstr. 11, D-07745 Jena, Germany.
ABSTRACT The wet-chemical synthesis of inorganic materials provides tools for generating nanostructures from particles to one-dimensional structures, but these conventional chemical techniques usually offer little control over the deposition of metals or metal particles into nanosized ring structures although interesting properties and applications, e.g., Aharonov-Bohm rings are expected. Our results provide a straightforward and rapid wet-chemical synthesis to ring-like metal particle arrays. Applying appropriate conditions, tubulin dimers, proteins of 45 nm diameter and a length of 8 nm, self-assemble by specific recognitions capabilities into defined superstructures. Ca2+ ions, e.g., direct the assembly of tubulin into 56 nm sized, ring-like structures. In our approach, these ring-like protein assemblies serve as a functionalized scaffold where the metal particles are generated in situ and deposited into spiral-shaped particle arrays, reflecting the arrangement of the protein subunits within the assembly. The resulting size and crystalline structure of the materials were examined using transmission electron microscopy and scanning force microscopy. INTRODUCTION One of the challenges facing chemists and materials scientists is the fabrication of well defined nanoscale materials, exhibiting interesting optical, electric, catalytic, or magnetic properties. Up to now, the wet-chemical synthesis of metallic nanostructures of controlled size and shape has been developed for generating nanostructures with various morphologies, from spherical nanoparticles, nanocubes [1], nanoprisms [2,3], nanoplates to nanobelts and nanorods [4]. These techniques, however, are based on direct crystal growth in solution and, thus, can only yield shape of simple topology, e.g., spheroids or polyhedrons. In contrast, nanostructures with a toroidal shape (nanorings) could not be produced by such a direct growth technique. Hence, the only way of producing ring-shaped nanostructures has been to use a toroidal template of nanoscale-dimensions. Nanoparticle arrays [5], mesoporous polymer membranes [6], or toroidal DNA condensates [7] have been applied as a primary template for fabricating Au or Ag rings, exhibiting outer diameters from 100 to 300 nm. We address the template-directed synthesis of ring-like nanoparticle arrays by applying toroidal protein assemblies. EXPERIMENTAL DETAILS Spiral assembly: Tubulin was isolated from porcine brain by temperature dependent assembly-disassembly cycles. Tubulin spirals were assembled from tubulin protein (final protein concentration ~1 mg/ml) in glycerine (0.5 M) by adding guanosine-5’-triphosphate lithium salt (0.5 mM) in the presence of Ca2+ ions and warming up the sample
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