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The study of interactions between particles organized in a linear configuration is interesting from a quantum mechanical perspective, and the anisotropic properties of linear assemblies is of potential interest for the development of solid-state devices. [1][2][3] This anisotropy may be manifested as a difference in the magnetization and coercivity obtained in a magneticnanoparticle array when a field is applied along the chain or orthogonal to it. [4,5] Nonlinear electrical characteristics [3] or dichroism in the optical spectra with longitudinal and transverse polarizations of light [6,7] in metal nanoparticle arrays are other examples of such anisotropy, and the construction of such arrays would offer opportunities in multiple applications. Engineering matter at submicron length scales has been an area largely dominated by top-down methodologies. Control of interparticle spacing in metal-nanoparticle arrays by using techniques such as electron beam lithography has been found to have a dramatic impact on the optical response of the nanoparticle assembly, [8][9][10] and has implications in fields such as plasmonics [11] and energy transport. [12,13] The use of templates such as carbon nanotubes [14] and linear pores [15] to construct one-dimensional nanostructures has been demonstrated previously. In addition, polymers have recently begun to play an increasingly active role as elements that can reproducibly direct the arrangement of nanoparticles into functional geometries. [16,17] Self assembling systems offer convenient yet powerful bottom-up strategies for the creation of nanostructures that can be deployed in the realization of functional nanoscale devices. [18,19] The utilization of biomolecules such as DNA, [3,[20][21][22][23][24] and protein-based materials [25][26][27] or viruses [28,29] to dictate the organization of nanoparticles has been shown to be an effective and robust paradigm. The use of peptide-based structures [30,31] in nanotechnology confers numerous advantages such as the specification of assembled nanostructure by changes in the primary sequence of the peptide, as well as the adoption of various hierarchical morphologies in solution. [32][33][34][35] This approach consequently permits the engineering of chemical functionality at precise positions in the nanoarchitecture of the assembled morphology. This functionality can be highly selective toward the binding of different inorganic materials [36] and may be engineered for biological recognition.[37] Herein, we demonstrate the construction of one-dimensional gold nanoparticle arrays with precise axial separations using self-assembling polypeptide fibrils. We elucidate the self-assembly of an alanine-rich polypeptide (designated 17H6) into fibrils that present regularly spaced charged patches along the fibril length. These positively charged patches are then utilized for the electrostatic binding of oppositely charged inorganic nanoparticles, thus resulting in linear nanoparticle arrays. The nanoparticles are immobilized on the fibril templa...

Thermal unfolding, reversible self-association, and irreversible aggregation were investigated for an alanine-rich helical polypeptide, 17-H-6, with sequence [AAAQEAAAAQAAAQAEAAQAAQ] 6. Dynamic light scattering, transmission electron microscopy, and thermal unfolding measurements indicate that 17-H-6 spontaneously and reversibly self-associates at acidic pH and low temperature. The resulting multimers have a compact, globular morphology with an average hydrodynamic radius approximately 10-20 nm and reversibly dissociate to monomers upon an increase to pH 7.4. Both free monomer and 17-H-6 chains within the multimers are alpha-helical and folded at low temperature. Reversible unfolding of the monomer occurs upon heating of solutions at pH 7.4. At pH 2.3, heating first causes incomplete dissociation and unfolding of the constituent chains. Further incubation at elevated temperature induces additional structural and morphological changes and results in fibrils with a beta-sheet 2 degrees structure and a characteristic diameter of 5-10 nm (7 nm mean). The ability to modulate association and aggregation suggests opportunities for this class of polypeptides in nanotechnology and biomedical applications.

h i g h l i g h t s g r a p h i c a l a b s t r a c tAqueous precipitation products of Zn(NO 3 ) 2 and NaOH were prepared. Synthesis route and lysozyme addition affected morphology of the products. Aqueous precipitation products of Zn(NO 3 ) 2 and NaOH obtained by changing the method of combining the reactants and by using lysozyme as an additive were investigated. In the case of single addition method, octahedral ε-Zn(OH) 2 and plate-like b-Zn(OH) 2 structures formed in the absence and in the presence of lysozyme, respectively. Calcination of these Zn(OH) 2 samples at 700 C yielded porous ZnO structures by conserving the template crystals. When zinc source was added dropwise into NaOH solution, predominantly clover-like ZnO crystals were obtained independent of lysozyme addition. Mixed spherical and elongated ZnO morphology was observed when NaOH was added dropwise into Zn(NO 3 ) 2 solution containing lysozyme. Lysozyme contents of the precipitation products were estimated as in the range of~5e20% and FTIR indicated no significant conformational change of lysozyme in the composite. These results suggest that lysozyme-ZnO/Zn(OH) 2 composite materials may have a value as an antibacterial material.