Interactions between cargo-carrying biomolecular shuttles

Microtubule shuttles propelled by the motor protein kinesin embedded in self-assembled monolayers are being developed for active transport functions in artificial microfluidic systems. As a model system, biotinylated microtubules have been laden with streptavidin-coated particles as cargo. The behaviour of cargo-laden microtubules has been observed using fluorescence microscopy upon activation of kinesin-driven transport processes. Collisions between mobile microtubules and their particulate cargo result in six distinct behaviours: bypass, microtubule bending, particle knock-off, particle transfers between nicrotubules, co-joining of microtubules to a common particle, and particle-induced severing of microtubules. The distribution of observed events can be described qualitatively on the basis of the mechanics of motor proteins and microtubules, the geometry of the collision events, and the loading rate dependence of the strength of microtubule-particle binding. Implications of the results for the use of motor proteins in active transport and cargo-handling systems for nanomaterials are described.