Assembly of Nanoparticle Ring Structures Based on Protein Templates

Abstract

Commercial requirements for miniaturized microelectronic devices provide strong motivation for exploring the synthesis of nanoscale systems using bottom-up techniques. The manipulation of charges at the single-electron level in regularly arranged nanoparticles can be utilized to create devices, such as switches, transistors, and digital electronic circuits.[1] An interesting feature of nanoscale ring systems is the AharonovBohm effect: interference phenomena of electron wave functions observed for electrons in ring systems. [2] Up to now, the bottom-up wet-chemical synthesis of inorganic materials has provided a tool for the fabrication of a range of nanostructures, from particles to one-dimensional (1D) structures, [3,4] but these chemical techniques offer little control over the deposition of metals or metal particles as nanometer-sized ring structures, even though interesting properties are expected for such structures. The growth of inorganic materials on biomolecular templates as well as biomolecule-directed assembly of inorganic building blocks are other promising strategies for fabricating complex functional nanostructures, such as wires and ring structures. [5][6][7][8][9] For example, wild-type and genetically engineered viruses have been used to template quasi-1D magnetic [10] and semiconducting nanowires [11] as well as ring structures of Au nanoparticles. [12] In this communication, we address the template-directed deposition of metals on ring-shaped tubulin assemblies for synthesizing metal ring nanostructures. The controlled deposition of metals on polymorphic tubulin structures, as already shown for microtubules (MTs), [13] have great potential for use in future electronic components, for example, AharonovBohm rings to be used in nanoscale circuits. Tubulin is a protein that forms a,b-heterodimers that are about 8 nm in length with diameters ranging from 4 to 5 nm. Tubulin molecules exhibit chemically active surfaces with defined patterns of amino acid side chains, which provide a wide variety of active sites for derivatization, especially for nucleation, organization, and binding metal particles. Tubulin is able to self-assemble into a wide variety of polymorphs: tubules, sheets, ribbons, spirals, and rings, [14] all consisting of differently arranged protofilaments with a strict alternation of a-and b-tubulin monomers. In the presence of Ca 2+ ions, tubulin assembles in vitro into rings and spirals instead of MTs. [15,16] Unlike tubulin rings, MTs have been used as templates to generate metal nanoparticles and nanowires, [13,[17][18][19] for the mineralization of iron oxide, [20] as well as for the kinesinbased transport of synthetic cargo [21][22][23] and CdSe quantum dots.[24]We have investigated ring and spiral formation by transmission electron microscopy (TEM, Fig. 1a). TEM images of tubulin rings fixed by 0.1 % glutaric dialdehyde (GA) and negatively stained by uranyl acetate reveal an outer and inner diameter of 56.4 ± 4.0 nm and 27.1 ± 3.8 nm, respectively, corresponding to a wall thickne...

Preparation of acacia‐stabilized silver nanoparticles: A green approach

“…In contrast to simple organic templates, biological macromolecules, 16,17 block copolymers, 18,19 dendrimers, [20][21][22] liquid crystals, 23 latex particles, 24 mesoporous inorganic materials, 25 microgels, 26 and hydrogels 27,28 have been employed as templates for producing well-dispersed nanoparticles.…”

Gum acacia as a facile reducing, stabilizing, and templating agent for palladium nanoparticles

“…8 Of the various strategies used, chemical reduction has proved to be an ideal strategy for the generation of uniform nanoparticles with a narrow size distribution via microemulsion, 9 coprecipitation, 10 carbon nanotube, 11 and polymer protection methods. [12][13][14] Biological macromolecules, 15,16 block copolymers, 17,18 dendrimers, 19,20 liquid crystals, 21 latex particles, 22 mesoporous inorganic materials, 5,23 microgels, 24 and hydrogels 25,26 have been used as templates for the production of well-dispersed nanoparticles. Metal nanoparticles have been extensively studied for many years because they usually exhibit unique properties and can be potentially used in many applications, including optics, 1 catalysis, 2 biodiagnostics, 3 and surfaceenhanced Raman scattering.…”

Single‐walled tubulin ring polymers

“…They can be used, for example, as models for understanding the self-assembly processes of other biopolymeric closed structures [18][19][20][21][22][23][24][25][26][27][28][29] or be considered as templates for producing ring structures with different materials as reported in Ref. 30.…”