Biological Examples of Nanomotors and Nanodevices

Biology provides examples of nanometer scale motors and electrical devices, which can be seen as limits of smallness. If nature can make these (only recently perceived) nanoscale machines, why, some ask, cannot human technology meet and eventually exceed these results? It is certainly a challenge.

The contraction of muscle occurs through the concerted action of large numbers of muscle myosin molecules, which "walk" along actin filaments in animal tissue.

Other sorts of motors rotate flagella, providing motion of bacteria through liquid media. Myosin, Kinesin, and rotary motors for flagella appear in extremely primitive life forms. It is believed that original forms of these proteins were present in single cell organisms appearing about a billion years ago. Simpler motors (similarly ancient) resembling springs are exemplified by the spasmoneme in Vorticdla.

Electrically controlled valves in biology are exemplified by ion channels. One of the most studied is the voltage-gated potassium channel. This protein assembly con-trollably allows potassium ions to cross the lipid membrane of a neuron, generating nerve impulses.

These ion channels can be compared to transistors, in that a voltage controls a current flow. Ion channels, embedded in lipid cell walls, are truly nanometer scale electrically controlled gate devices.

0 0

Post a comment