Natural micromachines get the points

By adapting life’s own microscopic machinery, some researchers hope to create minuscule factories that will churn out novel drugs and materials. In that quest, scientists have already commandeered mobile threadlike cell structures called microtubules as potential factory workers. But those wriggly strands have tended to wander aimlessly, preventing any useful work from getting done.

Arrows direct biological structures called microtubules (not shown) to slither one way along these circular grooves. Y. Hiratsuka et. al/Biophysical J.

Now, Taro Q.P. Uyeda of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, and his colleagues have devised a novel way to boss microtubules into following one-way paths. The trick is to construct routes with wee trail makers shaped like arrowheads.

In the past, researchers have deposited tiny ridges of polymers and other materials on glass. Coating those lines with so-called motor proteins made microtubules scurry along the ridges. That’s a reversal of the arrangement in cells, where motor proteins ferrying chemical cargo travel along a scaffolding of microtubules. In most of these earlier experiments, the mobile strands headed either way along the ridges and eventually strayed away from them.

Instead of making ridges, Uyeda and his colleagues etch steep-walled grooves into coatings deposited on glass plates. Then they use the grooves as microtubule tracks.

Microtubules moving along these channels rarely climb out, the researchers report in the September Biophysical Journal. Moreover, by punctuating the channels with arrowhead-shaped nodes, the scientists could make sure the microtubules all travel one way along the channels. When a straying microtubule reaches an arrowhead, it does an about-face, Uyeda notes.

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