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biophysics,application of various methods and principles of physical science to the study of biological problems. In physiological biophysics physical mechanisms have been used to explain such biological processes as the transmission of nerve impulses, the muscle contraction mechanism, and the visual mechanism. Theoretical biophysics tries to use mathematical and physical models to explain life processes. Radiation biophysics studies the response of organisms to various kinds of radiations. Biophysics has contributed important tools for the study of organic molecules, and especially of large molecules, which play an important part in biological processes. Paper chromatography, a direct development of adsorption techniques, is widely used to analyze tissues for chemical components. X-ray crystallography is used to determine molecular structures and has been useful with such problems as the complex structure of proteinsprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
..... Click the link for more information. . Among the optical methods used in the study of biological problems are photochemistry, light scattering, absorption spectroscopy (including the use of visible, ultraviolet, and infrared radiation), laserlaser
[acronym for light amplification by stimulated emission of radiation], device for the creation, amplification, and transmission of a narrow, intense beam of coherent light. The laser is sometimes referred to as an optical maser.
..... Click the link for more information. beams, and double refraction birefringence. These techniques and others permit the biophysicist to determine the structure of molecules in plants and animals to a degree not readily possible with ordinary chemical methods.
A hybrid science involving the overlap of physics, chemistry, and biology. A dominant aspect is the use of the ideas and methods of physics and chemistry to study and explain the structures of living organisms and the mechanisms of life processes. The recognition of biophysics as a separate field is relatively recent, having been brought about, in part, by the invention of physical tools such as the electron microscope, the ultracentrifuge, and the electronic amplifier, which greatly facilitate biophysical research. These tools are peculiarly adapted to the study of problems of great current importance to medicine, problems related to virus diseases, cancer, heart disease, and the like.
The major areas of biophysics are the following:
Molecular biophysics has to do with the study of large molecules and particles of comparable size which play important roles in biology. The most important physical tools for such research are the electron microscope, the ultracentrifuge, and the x-ray diffraction camera. See Molecular biology
Radiation biophysics consists of the study of the response of organisms to ionizing radiations, such as alpha, beta, gamma, and x-rays, and to ultraviolet light. The biological responses are death of cells and tissues, if not of whole organisms, and mutation, either somatic or genetic.
Physiological biophysics, called by some classical biophysics, is concerned with the use of physical mechanisms to explain the behavior and the functioning of living organisms or parts of living organisms and with the response of living organisms to physical forces.
Mathematical and theoretical biophysics deals primarily with the attempt to explain the behavior of living organisms on the basis of mathematics and physical theory. Biological processes are being examined in terms of thermodynamics, hydrodynamics, and statistical mechanics. Mathematical models are being investigated to see how closely they simulate biological processes. See Biomechanics, Biopotentials and ionic currents, Mathematical biology, Muscle proteins, Muscular system, Thermoregulation
(biological physics), the science that investigates the physical and physicochemical processes taking place in living organisms, and also the ultrastructure of biological systems on all levels of organization of living material—from submolecular and molecular to cells and entire organisms. The development of biophysics is closely connected with the intensive interpenetration of ideas, theoretical approaches, and methods of modern biology, physics, chemistry, and mathematics. The development of biology demonstrated that in order to understand and study elementary biological phenomena it is necessary to utilize the concepts and methods of the exact sciences. Such an approach is justified by the fact that, in the final analysis, all biological objects represent a collection of atoms and molecules and obey physical and chemical laws. But because biological systems are self-organizing systems that took shape in the process of evolution, many properties that do not take place in nonliving substances are intrinsic to them. The complexity of biological systems provides for the occurrence of processes that have only slight probability under the conditions usually considered in physics. Biophysics considers primarily complete systems and, as far as possible, does not break them down into chemical components. In connection with this, the necessity arises of revising the known physicochemical methods and creating highly specialized biophysical methods and procedures.
Modern biophysics, according to the classification accepted by the International Union of Pure and Applied Biophysics (1961), includes the following basic branches: molecular biophysics, which consists in the investigation of the physical and physicochemical properties of the macromolecules and molecular complexes that compose living organisms, and also the character of the interactions and the energetics of the processes that take place in them; cellular biophysics, which studies the physicochemical basis of cell function, the connection of the molecular structure of membranes and cell organelles with their functions and mechanical and electrical properties and with the energetics and thermodynamics of cellular processes; and the biophysics of control and regulatory processes, which deals with the investigation and modeling of the internal connections of control systems in the organism, their physical nature, and the physical mechanisms of life at the level of the entire organism.
However, the historically formed set of problems with which biophysics deals is broader. Subjects included in biophysics are the study of the influence of physical factors on the organism (vibration, acceleration, weightlessness) and of the biological effects of ionizing radiation, which in view of its importance and actuality has become the subject matter of radiobiology—a special science that has separated from biophysics. The physical analysis of the activity of the sensory organs (above all the optics of the eye); the analysis of the operation of the organs of motion, respiration, and circulation as physical systems; and questions of the strength and elasticity of tissues are essential, historically developed branches of biophysics. The development of physical methods of investigation of biological systems from macromolecules to the entire organism—without which modern biological research would be impossible—is also of great significance.
Individual research of a biophysical nature can be traced from the 17th century. In this period attempts were made to apply concepts established in physics and chemistry to the analysis of biological phenomena. The French scientist R. Descartes considered the human body as a complex machine. He published a number of works on the investigation of the sensory organs—bioacoustics and optics. The Italian scientist G. A. Borelli, a follower of Descartes, attempted to explain the motion of living beings by purely physical mechanisms. L. Eiler, a professor at the University of St. Petersburg, first described mathematically the motion of blood in the blood vessels. In 1756, M. V. Lomonosov introduced one of the first hypotheses on color vision. A strong impetus toward physicochemical research on living phenomena was given by the experiments of the Italian scientist L. Galvani, who showed the presence of “animal electricity.” In the second half of the 19th century, the German scientists H. Helmholtz and W. Wundt formulated the basic principles of physiological acoustics and optics. The German physician J. R. von Mayer, observing the saturation of hemoglobin by oxygen in human blood in tropical and temperate climates, formulated the law of conservation of energy. H. Helmholtz and M. Rubner continued the investigation of this law on living organisms. The works of the German scientists H. Helmholtz. E. Dubois-Reymond, D. Bernstein, and a number of others formed the basis for representations of the mechanisms of the origin of electrical potentials in tissues and the propagation of excitation along the nerve. The significance of the ionic composition and the reaction of the environment in the life of cells and tissues was explained in the works of the American researcher J. Loeb and the German scientists W. Nernst and R. Höber.
In Russia at the end of the 19th century, I. M. Sechenov studied the physical principles of the dissolution of gases in the blood and the biomechanics of motion. K. A. Timiriazev studied the photosynthetic activity of the separate regions of the solar spectrum in connection with the distribution of energy in it and the properties of the absorption spectrum of chlorophyll (1903). A. F. Samoilov described the acoustic properties of the middle ear. Credit for the development of the ionic theory of excitation (1916) belongs to P. P. Lazarev. M. N. Shaternikov used thermodynamic representations in studies of the energy balance of organisms (1910–20). Classical research was carried out from 1905 to 1915 by N. K. Kol’tsov on the role of physicochemical factors in the life of cells (surface tension, hydrogen ion and cation concentration). This phase of the prehistory of biophysics, which encompassed the 1920’s, is characterized by the appearance of individual works using the ideas and methods of physics and physical chemistry in the investigation of motion, the auditory and visual apparatus, photosynthesis, the mechanism of generation of electromotive force in nerves and muscles, and the significance of ionic media for the activity of cells and tissues.
After the October Revolution, favorable conditions existed for the development of biophysics in the USSR. In 1919, P. P. Lazarev created the Institute of Biological Physics in Moscow, where work was done on the ionic theory of excitation and the kinetics of reactions that take place under the influence of light, and studies were carried out on the absorption spectra and fluorescence of biological objects and also on the processes of primary action on the organism of various factors of the external environment. Later such institutes were created in other nations. In the 1920’s, Kol’tsov formulated the concept of the molecular structure of the gene and the concept of the matrix mechanism of transmission of hereditary information and synthesis of macromolecules. In the 1920’s and 1930’s, a number of books came out which had profound influence on the subsequent development of biophysics in the USSR: The Biosphere by V. I. Vernadskii (1926), Theoretical Biology by E. S. Bauer (1935), Physicochemical Principles of Biology by D. L. Rubinshtein (1932), The Organization of Cells by N. K. Kol’tsov (1936), and Reactions of Living Matter to External Excitations by D. N. Nasonov and V. Ia. Aleksandrov (1940).
In these years the gradual formation of the bases for biophysical research proceeded, new methods were developed, and the technical equipment of laboratories grew. In the USSR and the leading capitalist nations after World War II—as a result of the vast scope of investigations in physics and chemistry, the emergence of a powerful instrument-building industry, and a sharp increase in the funds for biological investigations—a vigorous development of biophysics began.
Formation of separate branches of biophysics. Molecular biophysics studies the mechanisms of biological phenomena from the point of view of the interactions of atoms and molecules, ions, and radicals. The investigation of the spatial structure and physicochemical properties of biological systems at the molecular level is part of the task of this field. These problems are closely connected with biochemistry; this is particularly clear in the example of the study of the structure of biologically important macromolecules, the explanation of whose spatial configurations requires a biophysical approach and is solved by the method of X-ray analysis. The latter was successfully used for the interpretation of relatively simple biological molecules. (In the 1920’s in England, W. Astbury succeeded in partially deciphering the structure of the cellulose molecule.) Work on the structure of protein was begun in the 1930’s by the English scientist J. Bernal. By 1954 the English researchers J. Kendrew and M. Perutz discovered a method of calculating the spatial location of atoms in protein molecules. This permitted the calculation of the structure of myoglobin and hemoglobin, which in turn made possible the discovery of the mechanism of development of sickle-cell anemia and a deeper understanding of the nature of the active center of a protein molecule. Work on the investigation of the spatial structure of proteins is being conducted in the USSR in the department of physics of Moscow State University, the Institute of Biophysics of the Academy of Sciences of the USSR, and other institutions. Investigations of the structure of fibrous proteins (collagen, the fibroin of silk) indicated the presence of a regular structure with periodically alternating amino-acid groups. A statistical theory of the reproduction (duplication) of deoxyribonucleic acid (DNA) has been developed. By 1968 the structure of almost 200 proteins had been determined. Together with the study of the construction of individual molecules, great progress was achieved in the investigation of molecular complexes—the ultrastructures that form the functional units of the cell.
Studies in molecular biophysics are closely connected with biochemistry, genetics, cytology, and molecular biology.
The problem of the excited states of molecules in biological systems occupies a significant place in molecular biophysics; such molecules acquire high chemical activity. Of the excited states that develop in the primary stages of photobiological processes, those which have received the most study are photosynthesis, vision, and bioluminescence.
The original trend in domestic biophysics can be taken to be the study of superweak ultraviolet radiation of biological systems (mitogenetic radiation; A. G. Gurvich, 1923–48). In the 1930’s, G. M. Frank and S. F. Rodionov developed a physical method of detecting the superweak radiance of biological objects. Progress in the development of methods of recording superweak light fluxes by means of photoelectric multipliers led in the 1950’s to the discovery of super-weak radiation of a number of animals and plants in the visible region of the spectrum. The connection of this radiation with the recombination of free radicals was shown. A. N. Terenin and his coworkers studied the mechanisms of elementary photophysical processes with the participation of pigments, demonstrated the role of molecular states, discovered the mechanism of migration of energy in them during photochemical reactions, and studied the mechanism of luminescence in proteins (1950–65). A. A. Krasnovskii discovered and studied the reaction of reversible photochemical reduction of chlorophyll and its analogues (1949–60). This work furthered the development of biological photochemistry.
In bioenergetics—one of the important branches of biophysics—the conversion of energy in living organisms is examined, beginning with the conversion and migration of energy at the molecular level and concluding with the energy balance of the whole organism. The mutual transformation of chemical and mechanical energy during the contraction of muscle fiber, the molecular mechanisms of motion of cilia and flagella in the protozoa, and the motion of protoplasm and cellular organelles have become the subject matter of mechanochemistry, which exists at the junction of biochemistry and molecular biophysics. In 1938, in the works of the Soviet scientists V. A. Engel’gardt and M. N. Liubimova, who studied the mechanism of muscle contraction, the presence of a direct connection between mechanical and chemical processes was demonstrated for the first time. This work was subsequently developed by the American scientist A. Szent-Györgyi.
A traditional branch of biophysics is the study of the physicochemical properties of cells and the permeability of biological membranes to different substances. An ever-increasing importance has been acquired by the problem of modeling artificial membranes and active ion transport. One example of the practical application of values obtained in this field of biophysics—by biochemistry and physiology—is the creation of the artificial kidney.
An important problem of biophysics is the investigation of bioelectric phenomena. In this field, biophysics is closely connected with physiology. Studies have shown that a potential difference of approximately 0.1 volt is maintained between the external and internal mediums of every living cell. The source of this difference is the ionic gradient between the external and intracellular mediums created by the cell. These data served as the basis for the creation of the membrane theory of the generation of potentials in the cell, introduced at the beginning of the century by the German scientist D. Bernstein and substantiated experimentally in the 1950’s and 1960’s in the work of the English scientists A. Hodgkin, A. Huxley, and B. Katz, who studied the variation of the permeability of the nerve fiber membrane and the ionic fluxes in the nerve during excitation. A significant place is also occupied by the investigation of other physico-chemical properties of cells—viscosity and optical properties and their variation under various physiological conditions and certain influences.
The biophysical principles characteristic of the organism as a whole are considered in the corresponding branches of bioenergetics (the study of the mechanism of heat transfer, heat insulation, and heat production; the rate of cooling under various conditions; and so on).
The biophysics of control processes is inseparably connected with biocybernetics and biomechanics. The creation of control systems and the explanation of the principles of the control of the movements of animals and man were initiated in the studies of the Soviet scientist N. A. Bernshtein. He was the first to set about the investigation of feedback in biological systems (1934). The study of the biomechanics of motions (walking, running, work motions, and so on), respiration, and blood circulation have exceptional importance in connection with questions of the physiology of work, sport, and cosmic flights, as well as in the study of the cause of cardiac and vascular illness and in the creation of apparatus for artificial respiration and blood circulation.
Biophysical investigations are conducted in the USSR at many scientific establishments; in particular, at the institutes of biophysics, cytology, and molecular biology of the Academy of Sciences of the USSR, in biophysics sub-departments at Moscow State University and Leningrad State University, and in other institutions. One of the first biophysics subdepartments in the world was founded at Moscow State University in 1953 by B. N. Tarusov. Studies in biophysics and the training of personnel are conducted in many nations: in the People’s Republic of China, at the Institute of Biophysics in Peking; in Czechoslovakia, at the Institute of Biophysics in Brno and Charles University in Prague; in the Federal Republic of Germany, at the Institute of Biophysics of the Max Planck Society in Frankfurt am Main, the Institute of Biological and Medical Physics at the University of Göttingen, and others; in France, at the Institute of Physicochemical Biology in Paris, the Institute of Macromolecular Studies in Strasbourg, and others; in the German Democratic Republic, at the Institute of Biology and Medicine in Berlin; in Great Britain, at the University of London and the Institute of Molecular Biology in Cambridge; in Hungary, at the University of Pécs; in India, at the Institute of Crystallography, Molecular Biology, and Nuclear Physics in Delhi and the University of Madras; in Israel, at the Weizmann Institute in Rehovoth; in Japan, at Osaka University, the Protein Institute in Osaka, and the University of Tokyo; in Poland, at the University of Warsaw and the Institute of Biochemistry and Biophysics of the Academy of Sciences of the Polish People’s Republic; in Rumania, at the Institute of Biophysics in Bucharest; in Sweden, in the Division of Biophysics at the Nobel Institute in Stockholm; and in the USA, at Yale University, the Massachusetts Institute of Technology, the University of California, Harvard University, the Rockefeller Institute, and many others.
At the First International Biophysics Congress, held in Stockholm in 1961, the International Union of Theoretical and Applied Biophysics was created, with representatives of the USSR in its central council.
Periodical publications in which works in biophysics appear are the following: Biofizika (Moscow, 1956—), Molekuliarnaia biologiia (Moscow, 1967—), Radiobiologiia (Moscow, 1961—), Advances in Biological and Medical Physics (New York, 1948—), Biochimica et Biophysica Acta (New York-Amsterdam, 1947—), Biophysical Journal (New York, 1960—), Bulletin of Mathematical Biophysics(Chicago, 1939—), Journal of Cell Biology (New York, 1962—; called the Journal of Biophysical and Biochemical Cytology from 1955 to 1961), Journal of Molecular Biology (New York-London, 1959—), Journal of Ultrastructure Research (New York-London, 1957—), and Progress in Biophysics and Biophysical Chemistry (London, 1950—).
REFERENCESBernshtein, N. A. O postroenii dvizhenii. Moscow, 1947.
Lazarev, P. P. Sochineniia, vol. 2. Moscow-Leningrad, 1950.
Bresler, S. E. Vvedenie ν molekuliarnuiu biologiiu. Moscow-Leningrad, 1966.
Molekuliarnaia biologiia (collection of articles). Moscow, 1963. (Translated from English.)
Pasynskii, A. G. Biofizicheskaia khimiia. Moscow, 1963.
Ackerman, E. Biofizika. Moscow, 1964. (Translated from English.)
Voprosy biofiziki: Materialy I Mezhdunarodnogo biofizicheskogo kongressa: Stokgol’m, iiul’-avgust 1961. Moscow, 1964.
Setlow, R, and E. Pollard. Molekuliarnaia biofizika. Moscow, 1964. (Translated from English.)
Vol’kenshtein, M. V. Molekuly i zhizn’: Vvedenie ν molekuliarnuiu biofiziku. Moscow, 1965.
Biofizika. Moscow, 1968.
Casey, E. Biophysics: Concepts and Mechanisms. New York-London, 1962.
Physical Techniques in Biological Research, vols. 1–5. New York, 1955–64.
B. N. VEPRINTSEV