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W8.7.1

Nanowiring Enzymes to Carbon Nanotube Probes

C.P. Collier, M.J. Esplandiu, V.G. Bittner, and I.R. Shapiro California Institute of Technology Division of Chemistry and Chemical Engineering ABSTRACT The observation of spectroscopic signals in response to mechanically induced changes in biological macromolecules can be enabled at an unprecedented level of resolution by coupling single-molecule manipulation/sensing using carbon nanotubes with single-molecule fluorescence imaging. Proteins, DNA and other biomolecules can be attached to nanotubes to give highly specific single-molecule probes for the investigation of intermolecular dynamics, the assembly of hybrid biological and nanoscale materials and the development of molecular electronics. Recent advances in nanotube fabrication and Atomic Force Microscope (AFM) imaging with nanotube tips have demonstrated the potential of these tools to achieve high-resolution images of single molecules. In addition, proof-of-principle demonstrations of nanotube functionalization and attachment of single molecules to these probes have been successfully made. Improved techniques for the growth and attachment of single wall carbon nanotubes as robust and well-characterized tools for AFM imaging are being developed. This work serves as a foundation toward development of single-molecule sensors and manipulators on nanotube AFM tips for a hybrid atomic force microscope that also has single-molecule fluorescence imaging capability. An individual single wall carbon nanotube (SWNT) attached to an AFM tip can function as a structural scaffold for nanoscale device fabrication on a scanning probe. Such a probe can have a novel role, to trigger specific biochemical reactions or conformational changes in a biological system with nanometer precision. The consequences of these perturbations can be read out in real time by single-molecule fluorescence and/or AFM sensing. For example, electrical wiring of single redox enzymes to carbon nanotube scanning probes will allow for observation and electrochemical control of single enzymatic reactions, by monitoring fluorescence from a redox-active cofactor or the formation of fluorescent products. Enzymes “nanowired” to carbon nanotube tips may enable extremely sensitive probing of biological stimulus-response with high spatial resolution, including product-induced signal transduction. INTRODUCTION Recent developments in two key technologies, single-molecule fluorescence imaging and single-molecule nanomanipulation, have directly revealed the dynamic behavior of biological molecules such as motor proteins, enzymes and cell-signaling proteins.1 Single-molecule fluorescence imaging employs fluorescent tags to measure conformational changes in single biomolecules, most often using a far-field optical microscope. The extreme sensitivity of single fluorophores to the presence of other fluorophores or quenchers, and the fact that they have individual transition dipoles, provides real-time information on dynamic changes in orientation and distance. Single