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Unidirectional transport of a bead on a single microtubule immobilized in a submicrometre channel

Artificial nano-scale transportation is demonstrated by reconstructing the intracellular transport in a living cell. The transport system is established on two novel techniques: one is the introduction of a single microtubule filament with controlled polarity in a microfabricated submicrometre channel; the other is the immobilization technique of microtubules by a mercury lamp. To transport a kinesin-coated bead in a designated direction, each microtubule filament is polarly oriented by in vitro gliding assay, in which microtubules are carried by the movement of kinesin immobilized on the channel surface. Then, microtubules are immobilized by exposing kinesin to the mercury lamp, which inactivates kinesin but not microtubules. A kinesin-coated bead is newly introduced and carried on the microtubule from one end of the channel to the other as designed. This is an essential component to build up an integrated nano-scale transport system driven by motor proteins.