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companies and the NIH have invested many million of dollars in instrumentation at these facilities to support this kind of research.

Knowing the structure of proteins is essential for understanding their function, but we must also learn how parts of proteins move as they carry out their tasks. Biophysicists have combined the methods of modern molecular biology with sophisticated physical techniques to learn just how many types of proteins do their job. All cells contain tiny molecular motors—these motors are a large family of proteins—that help the cell to move or that move material within the cell from one place to another. The most familiar manifestation of these motors at work is muscle contraction and the pumping of the heart, but molecular motors are essential for the jobs performed by all cells, from the dividing of cells to produce replacements for cells that die to the carting of essential chemicals to where they are needed in the brain (see sidebar “Optical Tweezers”). Unraveling how these motors work has required developing clever physical methods to measure the motions of single protein molecules over distances that are smaller than can be seen with microscopes.

The beating of the heart and all functions of the brain require another kind of protein that produces electrical signals in cells. The electrocardiogram and the electroencephalogram are manifestations of the operation of these proteins and are used for the diagnosis of heart and neurological diseases. Biophysicists have also learned how these proteins generate their electrical signals, and this knowledge has given us many therapies, ranging from drugs to treat abnormal heartbeats to the treatment of epilepsy.

SUMMARY

In small ways and large, from the treatment of nearsightedness to the diagnosis of neurological diseases, applications of the discoveries of physics have revolutionized medical practice. Although this transformation began 100 years ago, it has greatly accelerated in the past several decades as our increased ability to process information has been applied to a variety of physical phenomena. In the 21st century, physics will continue to provide the foundation for striking advances in biomedicine and health. The increasingly interdisciplinary nature of physics research is focusing more of the field's intellectual and technical resources on addressing opportunities in biology and medicine, both to increase our understanding of basic mechanisms and to provide novel technologies for research and application. In the coming decades we can confidently expect that physics will continue to contribute to the nation's health and, in fact, that these contributions will increase.



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