Accelerated Degradation of Active Nanosystems by Biomolecular Motors

The research objective of this award is to develop an understanding of the degradation pathways of active nanosystems. At the macroscale, a car engine will rust when inactive, but wear out when running. Similarly, active nanosystems which incorporate mechanical motion degrade faster when activated. This project will utilize molecular shuttles, nanoscale transport systems powered by the motor protein kinesin, as a model system. Microfabricated guiding structures will be used to exert defined, cyclic loads on the moving shuttles, and optical microscopy will be employed to observe the breaking of the central part of the shuttle. Investigating degradation within these active

nanostructures explores new ground, since the molecular shuttle system is too large to be readily described in atomic-level terms of force-activated dissociation of single bonds, but too small to apply macroscopic concepts of wear and fatigue. Thus a mesoscale view of these systems on the nanoscale is required and will be developed through a combination of experiment,simulation, and theory.

The result of this research will be an improved understanding of wear and fatigue at the nanoscale. This understanding is on one hand critical for the design of durable devices which can function for their intended lifetime without failure. On the other hand, degradation products may be released from the system, similar to the ?brake dust? created from brake pads in a car. To assess the potential environmental and toxicological impact of active nanosystems it is therefore important to understand how the nanosystem evolves over its lifetime and ultimately fails. While this research is only a first step towards understanding these complex processes, it will ? if successful ? create a template for the evaluation of other active nanosystems and provide a basic scientific framework to understand these degradation processes.