A challenge for nanotechnology is the dynamic and specific control of nanomachines by the user. Molecular shuttles, consisting of cargobinding microtubules propelled by surface-immobilized kinesin motor proteins, are an example of a nanoscale system that ideally can be selectively activated at programmable locations and times. Here we discuss a biomimetic solution where activating molecules are delivered locally via photolysis of a caged compound and subsequently sequestered in an enzymatic network. The controlled sequestration of the activator not only creates a rapid deactivation when the stimulus is removed but also sharpens the concentration profile of the rapidly diffusing activator. This improvement comes at the expense of a reduced efficiency in the utilization of the activator molecules, suggesting that these nanosystems are most efficiently addressed as a swarm rather than as individuals. Our work represents a step toward transferring the cellular control strategies of molecular activation to bionanotechnology.Bionanotechnology is concerned with the utilization of biological components in nanotechnology, 1 which to a varying degree necessitates the use of biological engineering approaches in a wider sense, for example, in the use of selfassembly to create extended structures. However, a striking accomplishment of nature is not only to create nanomachines and weave them into larger structures, but also to control their spatial and temporal activation via specific signals. This controlled activation is often achieved through the delivery of small molecules, whose spatial and temporal distribution is shaped by the actions of multiple enzymes releasing or sequestering the activating species. Examples include intracellular signaling via calcium, 2,3 NAD(P)H, 4 or cAMP.
5In contrast, the dynamic and controlled activation of specific nanomachines has been addressed in a technological context primarily by making light-activation an integral part of the design as in the light-driven synthetic motors based on rotaxanes or catenanes 6 or by designing devices that can be individually activated with a highly specific fuel molecule. 7 A new, chemical approach is to exploit reactiondiffusion systems to locally change buffer conditions and activate enzymes. 8 Here, we present a biomimetic approach to dynamically control motor protein-driven bionanodevices 9 in particular kinesin-driven molecular shuttles. 10 Molecular shuttles consist of a surface patterned with stationary kinesin motors and cargo-binding microtubules transported by the motors. Localized release and enzymatic sequestration of the substrate ATP creates a spatially and temporally well-defined concentration profile, which in turn leads to controlled activation of a small number of molecular shuttles, as shown in Figure 1. This approach significantly expands the scope of previous work, 11 which demonstrated that repeated, stepwise activation of kinesin-driven molecular shuttles can be achieved by A nearly cylindrical cone of UV light is produced ...