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Biomolecules and Nanotechnology

Evolution has forced innovative solutions to biomolecular problems. Some may inform the growing field of nanotechnology

David Goodsell

The term "nanotechnology" commonly refers to a speculative field that proposes to build machinery so small its components are measured on a scale of billionths of a meter (nanometers) using many of the principles of macroscopic engineering. In his books, K. Eric Drexler has popularized the design and computer modeling of many of these machines, including nano-scale manipulators to build objects atom by atom, bearings and axles built of diamond-like lattices of carbon, waterwheel-like pumps to extract and purify molecules and tiny computers with moving parts whose size is within atomic scale. The goals of these compelling machines are precision, with every structure and action controlled at the level of individual atoms, and parsimony, performing tasks at the minimum size necessary.

Figure 1. Biomolecular machines . . .Click to Enlarge Image

You might be surprised to learn that nanotechnology was perfected more than three billion years ago. Indeed, working examples of each of these machines exist today within living cells. Nanoscale manipulators for building molecule-sized objects were discovered by the earliest cells and are now used to build proteins and other molecules atom by atom according to defined instructions. Rotating bearings are found in many forms: Clamps that encircle DNA and slide along its length may be found in the simplest bacteria. Our own cells contain a rotary motor used not to power motion but instead to generate energy. Cells use a large collection of molecule-selective pumps to import ions, amino acids, sugars, vitamins and all of the other nutrients needed for living. Cells also use molecular computers, which, by altering their shapes, "read" the concentration of surrounding molecules and compute the proper functional outcome. By evolutionary search and modification over trillions of generations, living organisms have perfected a plethora of molecular machines, structures and processes. Figure 2 presents a few examples of the rich bio-nanotechnology that may be found in every modern cell.

Figure 2. Using a few basic structural plans . . .Click to Enlarge Image

Biological molecules are proven examples of the feasibility, and the utility, of nanotechnology. Our lives depend on them. They are foreign, however, to our everyday experience, with unusual organic shapes and unfamiliar properties. Bio-nanomachines are often the same size and complexity as the speculative nanomachines being designed today, but they bear little resemblance to the machinery of our macroscopic world. Eric Drexler's nanomanipulators and gears seem more familiar, because they are built by engineers along the familiar rigid, rectilinear designs of our macroscopic world. To understand the organic, flexible forms of bio-nanomachines, we must forget the processes of design and engineering in our familiar world and look instead at the forces that shaped the evolution of life.

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