Creation of a Nanometer-Scale Toolbox for Molecular Motor Transport-Circuits

Abstract: This thesis presents studies of molecular motors in interaction with nm-scale structures, as well as the development of a set of tools that can be used for the construction of custom-designed nano-transportation systems. In our studies, we have used the latest nanoscale technology and combined this with advanced results from chemistry and biomedical sciences. We have succeeded in transferring biomolecules from their natural habitat to an artificial environment created on a silicon-chip. The molecules - motor proteins myosin and actin - were maintained in their fully functional state by controlling the surface morphology and chemistry of the chip environment with nm-scale precision. These proteins are nanomachines, capable of transforming chemical energy into mechanical work. Our work has been concentrated on the introduction and development of a toolbox concept. A set of nm-scale tools, or components, have been defined and created, each with their unique basic transport function. The custom-designed components have been constructed as independent building blocks that can be combined into any circuit design of for example motor-driven micro-laboratories. The designing can be performed without detailed knowledge of the underlying mechanisms, e.g. lithography or motor protein biochemistry. To some extent, the concept resembles that of micro-electronics. The key components in the toolbox have been constructed of molecular monolayers and lithographic resist. We have found that monolayers of trimethylchlorosilane can be used to make conventional semiconductor materials, such as silicon, biocompatible. Furthermore, we have created a three-dimensional resist structure on the surface of a silicon-chip, that have been used to guide the mechanical motion developed by the motor proteins. With this novel design we have reduced the degrees of freedom for the proteins so that the effective guidance precision has increased successively from millimeter-, to micrometer- and eventually nanometer scale. Principally, electron-beam lithography has been used for the fabrication of the samples, although nano-imprint lithography has also been demonstrated as a powerful tool for parallel massive production on a commercial scale. In a series of experiments we have fine-tuned and characterized the properties of each toolbox component. Tools have been developed to capture and stream the molecular motors, reroute them and to analyze them. We have also demonstrated how cargo can be attached to the filaments, and performed successful experiments with chemically-linked quantum dots.