Little Motors, Big Designer

Little Motors, Big Designer

As a student I came across the humorous definition of a nuclear physicist as one who was “learning more and more about less and less, until finally he knew everything about nothing.” In today’s world of research, this reference to the wonders of nature at its tiniest levels could also be said about the biologist. Every day we are treated to new discoveries revealing the amazing intricacies of the biological cell and the molecular machines that govern its functionality, all at a size that requires an electron microscope to even begin to see.

In the middle of last year, Science Magazine published a fascinating review article on the subject of molecular motors and their use in nanotechnology. In the first part of the article, the authors point out how the cell is best described as a miniature factory where literally thousands of machines perform various specialized tasks. These functions include: allowing the cell to replicate itself in under an hour (what factory do you know of that can perform this feat?), proofreading and repairing errors in its own manufacturing instructions (DNA), sensing its environment and responding to it, changing its shape and morphology, and obtaining energy from photosynthesis or metabolism.

To accomplish all of these tasks, the cell has a wide variety of specialized molecular motors that are direct analogs of the kind of devices that engineers design and build for man-sized factories. These include: “electric” motors having stators, rotors, shafts, bearings and universal joints; transport “trucks” that provide stepwise motion along “highways” called microtubules or filaments; and pumps made from tubes and cams that force fluids along the tubes. The major differences between these molecular motors and those made by humans are their size (a billion times smaller) and their efficiency (near 100 percent vs. 65 percent, at best).

If biomolecules can be successfully integrated into nanotechnology devices, there are several advantages, including the self-assembly characteristics of protein-based machines, the possibility of using other biological components from nature, and the fact that the processes for manufacture are environmentally benign and occur under mild conditions.

Research efforts in nanotechnology over the past several decades have produced various components of the machinery, like cogwheels or pumps, but have not yet been able to produce the motors needed to make the machinery go. The article asks whether the nano-machines found in nature can be used directly or serve as templates. So far, results indicate protein motors can be interfaced and made to drive the man-made nanoscale components but have limited lifetimes of only a few days. To date, no usable devices have been made. However, in the near future it is likely that progress will be made using the parts from cells, eventually allowing researchers to build tailor-made devices for the sorting of materials, assembly of different materials, concentration of materials for enhanced detection, along with many of the functions performed within cells.

One thing is clear: the machines found in cells are absolutely remarkable in their characteristics, challenging the minds and creativity of the most advanced researchers in nanotechnology. Yet, they are almost identical in form (but superior in efficiency and size) to the mechanical devices that the best engineers design for everyday life. Surely the biomachines found in cells require a level of intelligent design far greater than what man has accomplished!