Noncovalent sidewall functionalization of single-walled carbon nanotubes for protein immobilization

Spontaneous reduction of metal ions on the sidewalls of carbon nanotubes

Nanotube/nanoparticle hybrid structures are prepared by forming Au and Pt nanoparticles on the sidewalls of single-walled carbon nanotubes. Reducing agent or catalyst-free electroless deposition, which purely utilizes the redox potential difference between Au3+, Pt2+, and the carbon nanotube, is the main driving force for this reaction. It is also shown that carbon nanotubes act as a template for wire-like metal structures. The successful formation of the hybrid structures is monitored by atomic force microscopy (AFM) and electrical measurements.

Structural characterization, optical properties, and improved solubility of carbon nanotubes functionalized with Wilkinson's catalyst

Oxidized carbon nanotubes have been reacted with Wilkinson's complex. It has been found that the Rh metal coordinates to these nanotubes through the increased number of oxygen atoms, forming a hexacoordinate structure around the Rh atom. The reaction process increases oxidized nanotube solubility in DMSO (>150 mg/L) as well as to a certain extent in DMF and THF. The functionalization process results in exfoliation of larger bundles of SWNTs and may select for the presence of distributions of smaller-diameter tubes. Optical data on the derivatized adducts suggest the possibility of interesting charge-transfer behavior across the metal-nanotube interface. An application has been made of this system as supports for homogeneous catalysis.

Molecular dynamics analysis of a buckyball-antibody complex

This is a multinanosecond molecular dynamics study of a bio-nano complex formed by a carbon nanoparticle, a buckyball C(60), and a biological molecule, an antibody, with high binding affinity and specificity. In the simulation, the ball is completely desolvated by the binding site of the antibody by means of a nearly perfect shape complementarity and extensive side-chain interactions, with the exception that about 17% of the surface is persistently exposed to solvent and could be used for functional derivatization. The interactions are predominantly hydrophobic, but significant polar interactions occur as well. There exists a rich body of various pi-stacking interactions. Aromatic side chains are involved in both double and triple stackings with the ball. Some ionic side chains, such as the guanidinium group of arginine, also form pi-stackings with the ball. The results suggest that pi-stackings are very efficient and common modes of biological recognition of pi-electron-rich carbon nanoparticles. Most importantly, the results demonstrate that, in general, an ordinary protein binding site, such as that of an antibody, can readily bind to a carbon nanoparticle with high affinity and specificity through recognition modes that are common in protein-ligand recognition.