Biophysics, interdisciplinary study of biological phenomena and problems, using the principles and techniques of physics. The science of biophysics developed after World War II, stimulated in part by the application of nuclear physics to biological systems, including the investigation of radiation effects on living matter. In the course of these studies, physicists were introduced to biologists and biological problems, and biophysics evolved as a new scientific field.
Today biophysics is closely related to a number of biological disciplines, including biochemistry, genetics, molecular biology, microbiology, physiology, neurobiology, histology, and virology. An extension of physics and physical chemistry, biophysics relies on techniques derived from the physical sciences but focuses on biological problems.
An important area of biophysical study is the detailed analysis of the structure of molecules in living systems. The best-known achievement in that respect is the model of deoxyribonucleic acid (DNA), the hereditary material of life. This model forms the basis of the greatest accomplishments of molecular biology and genetics in recent years and was formulated from X-ray crystallographic data. Similar crystallographic techniques have proved invaluable in determining the structures of myoglobin and hemoglobin, which are oxygen-binding pigments of muscles and red blood cells, respectively, and of such enzymes as lysozyme and ribonuclease.
Another important area of biophysics has been the study of information transmittal, in the form of impulses, in the nerve cells of organisms. Such information is transmitted as discrete events, called action potentials, and is specified by the frequency at which these are transmitted and by the connections each nerve cell makes with its neighbors. For example, the British biophysicist Alan Lloyd Hodgkin and the physicist Andrew Fielding Huxley studied nerve cells of the squid, whose large size permits the insertion of several electrodes directly into the cell interior. With a judicious combination of electrochemistry, modern electronics, and mathematical modeling, they were able to show that the action potential is caused by selective changes in the permeability of the cell membrane to sodium and potassium. The technique has since been applied with minor modifications to other excitable tissues and has come to form the basis for all modern attempts to understand the function of the central nervous system.
The domain of biophysics today can encompass biological subsystems that are so small that they are best studied with the techniques of quantum mechanics. It can also be applied to larger biological systems and their interactions, as among several organs of the body, which can be analyzed by control theory.
