Quarterly Reviews of Biophysics II, 4 (1978), pp. 629-635 Printed in Great Britain

Opening Address by the President of IUPAB 3 September 1978 V I T H CONGRESS INTERNATIONAL U N I O N OF PURE AND APPLIED BIOPHYSICS

President of the Science Council, of Congress, Chairman of the Organizing Committee, Chairman of the Programme Committee, Ladies and Gentlemen, and students (who are also ladies and gentlemen): I offer my thanks to the Japanese organizing and program committees, especially my dear friends Professor Kotani, Setsuro Ebashi, Fumio Oosawa and the others whom you find listed in the program. They have thoughtfully and independently selected from many suggestions twenty-four symposia and several speakers of international fame for each one, to such good results that the list of twenty-four symposia is an excellent guide to new directions in biophysics. However, each one of us has his own personal intuition as to 'where to go' in science - and in fact that is the great strength of individualistic investigator-initiated research programmes - no single leader and no select committee can match the collective genius of the world constituency of scientists! Thus, I am bold enough to present my personal views, endorsed by no one. I should also state that this is not a plenary lecture, it is only an outline of the topics that I think will be of importance in the science of pure and applied biophysics. My departure to new directions and my presence here has as its perspective 20 years of pleasant contacts with Japanese science. My first visit was to Tokyo and Kyoto to participate in the Japanese Science Council's International Symposium on Enzyme Chemistry. Indeed, two of the symposium speakers at that meeting are now your past and current president. They attempted to predict the future of their fields; Professor Lynen prognosticated that' details of the topography of living cells' would be needed and I seem to have stressed 'metabolic mechanisms' and' metabolic health'. However, it was a time of new directions and of innovation in biophysical techniques: X-ray crystallography

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was about to give us enzyme topography, the NMR technique was about to give us the geometry of active sites of enzymes, and the laser was about to afford a kinetic dissection of electron transfer reactions involving electron, molecular and nuclear tunneling. So new directions in biophysics are closely linked to technical developments and innovations in Physics. But more important to the biophysicist than the technique is the nature of the scientific problem - a technique is useful because it solves a problem - so let me list problems that I think may be important. Biological structure comes high on my priority list, yet present research is limited to snapshots of the dynamic pictures. The dynamic aspects are now of great interest: good time resolution and chemical specificity are required in structure determinations in crystalline and amorphous proteins and enzymes, and distinction must be made between enzymes and substrates in soluble and in membrane-bound proteins. Correlations of structural and chemical changes in the very short time range of elementary, primary events, together with comprehensive theories of nuclear and electronic processes that are ratedetermining in biological reactions, are of great current interest. And the words 'applied biophysics' in the Union's title suggest appropriate studies of environmental and medical problems. I choose to emphasize the medical aspects - for example, tissue-imaging procedures that diminish or eliminate body exposure to dangerous radiation, and the perfection of innovative non-invasive non-destructive diagnostic methods for clinical use, are useful new directions. So the future of biophysics requires new approaches, new technologies, and usually new physical instruments, and indeed these three are emerging nearly continuously in modern physics. As an example let us consider radiation itself as one of the most general ways of probing biological structure and function, but such studies have been limited by both the intensity (brightness) and the energy (wavelength) of radiation available. One example of current progress in pure physics that is of interest to biology is progress on the Large Torus experiment at Princeton, reported this week. A hydrogen-and-deuterium plasma reached a temperature of 60 million degrees for 20 milliseconds - this represents a flash of intense continuous radiation from infra-red to less than 1 A - a performance that outshines the already super-bright and continuous light obtainable from the Stanford Synchrotron storage ring, sometimes called 'National Light Source', one of which you will soon

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have in Japan, too. Such bright radiation can be extremely useful in Xray structure determinations, because the intensities are about a million times greater than the best conventional X-ray sources. Lasers give more powerful and shorter light pulses at longer wavelengths, i.e. of several thousand angstroms - too long for atomic structure determinations, but appropriate for molecular size determinations and for early events in photobiology. Short intense flashes of monochromatic light as obtained from a synchrotron storage ring or from a mode-locked solid-state or liquidstate laser have extended the range of kinetic, mechanistic studies to the very borders of the physical knowledge of excitation processes, both in photobiological systems and in the study of the photochemistry of enzyme-ligand compounds. And at the borders of physics and chemistry, classical processes and classical mechanics are more clearly resolved from quantum processes. A particularly important case in biology is the departure from the Arrhenius 'over the barrier' transfer of electrons and protons to a quantum mechanical 'through or under the barrier' tunnelling processes at rates sufficient for biological function - for example, in cytochrome c oxidation in photosynthetic bacteria, the laser-flash-activated reaction centres transfer millions of electrons per second by a tunnelling process. Indeed, often a biochemical application follows closely a physical breakthrough. Tunnelling theory itself appeared just a few years after the emergence of modern quantum theory. Tunneling under the energy barrier in radioactive decay involving a-particle formation revolutionized ideas on nuclear disintegration, and to paraphrase Gurney and Condon, ' the a particle slips [through] the barrier almost unnoticed'. In solid-state electronics Japan should properly be proud of Esaki's invention of the 'tunnel diode'. Such a case might be considered analogous to the above-mentioned electron conductivity (we call it electron transfer) observed between cytochrome c and the laserflash-activated reaction centre of the photosynthetic bacteria. Highly simplified quantum-mechanical concepts explain the biological data: a rectangular barrier 30 A wide and 1 eV high affords electron tunnelling at the observed rate of 2000 times per sec at 4 °K in photosynthetic bacteria. Tunneling may be nature's way of solving the problem of electron transfer over longer distances than are possible by the Arrhenius ' over the barrier' process. Macromolecular architecture, especially that of

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two-dimensional planar systems represented by immobilized macromolecules embedded in membrane lipid, requires not only electron transfer over long distances, but also specificity and the rate control necessary for biological function in bioenergetics, biosynthesis and possibly information transfer. Thus the constraints on distance between active centres were diminished so that instead of distances of a few angstroms, distances of up to 30 A and perhaps more are feasible, and many more structural possibilities may have a biological function. The nuclei of atoms between which an electron tunnels may themselves shift a few hundredths of an angstrom to new positions before tunneling occurs. Thus the state of the nucleus can control the rate. And in addition, energy-level matching on both sides of the tunneled barrier may afford recognition or specificity factors essential for biological control. Edge absorption spectra characterize the charge state of the metal atom, and exafs identifies the distance to and, in some cases, the nature of the neighbouring atoms. With the aid of synchrotron radiation and improved detectors, both these techniques can now be applied in the millimolar, and in the future to the submillimolar concentration ranges of metallo-enzymes. Time resolution of changes in charge density and distances in edge and exafs studies seems possible due to the pulse nature of the synchrotron radiation, which has nanosecond duration and microsecond repetition intervals. For example, time-resolved structural data may be obtained by repetitive flash photolysis of haem-CO compounds in synchrony with the synchrotron pulses. X-ray crystallography at low and high angles becomes a more rapid and selective process using synchrotron radiation; for example, as in the case of anomalous diffraction of monochromatic X-rays specifically absorbed at the K edge of one or more metal atoms in a metalloenzyme, or of a heavy metal derivative of a non-metalloenzyme. This will help solve the phase problem for the total crystal structure and locate the heavy atoms as well. Again the availability of pulsed intense X-rays suggests their use on time-resolved structure determinations. The study of the cell constituents is traditionally based upon the historic approach, used particularly well by Otto Warburg in the 1930s, involving cell and organelle rupture, homogenization, extraction, isolation, purification and crystallization of cell proteins and enzymes. In fact, nearly 1000 enzymes have been isolated by these methods, and X-ray crystal structures are available on many. But the natural environ-

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ment of all the molecules was destroyed by the preparative method. Now we need the answer to a more penetrating question: how are such enzymes arranged in their natural state, and how do they interact within the cytoplasm of the cell, in the matrix space organelles, and in the lipid membranes? Indeed, what are the supramolecular structures? For this question we need non-destructive biophysical methods that provide biochemical and structural assays of enzyme function in the living cells and organelles. Non-destructive optical methods have served well to measure the kinetics and reactivities of pigmented enzymes in cells, but we have not adequately applied structural methods to these problems of supramolecular biology. A logical extension of such non-destructive approaches to cell function is their non-invasive character - and here we see another useful facet when considered in connection with studies of the organs of animals and man. Not only is the structure and function of the organ preserved during the non-destructive analytical procedure, but the trauma of the destructive analytical procedure is avoided. In fact, reliance upon historical methods has led to the acceptance of medical procedures that are often painful, and even undignified. Thus biophysics of the future may offer to medicine and biology less invasion, less destruction and a more direct and precise information on normal and diseased states of tissues and organs of the body. One especially destructive biophysical tool is X-rays, and the doses of irradiation that the cells of the body can tolerate are limited. Highenergy radiation used for computer-tomography 3D-scans of tissue density involve damaging interaction of radiation with tissue molecules that can lead to cancer. Lower-energy radiation can be now used energies so low that the chemistry of the tissue is undisturbed. Ultrasound, for example, currently provides 3D images of the larger body structures and is employed increasingly in the study of the radiationsensitive fetus. One could greatly improve imaging methods if they were specific for any one of the body chemicals. Visible and infra-red light is specifically absorbed by cell pigments that are involved in tissue-oxygen metabolism, and 2D (two-dimensional) reflectance or fluorescence scanning of the surface layers of organs which are exposed in the course of surgical blood-vessel repair in the heart to avoid cardiac infarcts, and in the brain to avoid stroke, is now in progress in several medical centres. Such non-destructive techniques provide immediate information on

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the possible improvement of tissue-oxygen metabolism due to blood vessel surgery. Chemical signals from deep within the body tissues are obtainable with the lowest energy level of perturbation, namely that of the nuclear spins. Thus, nuclear magnetic resonance seems an innocuous procedure. Water is the most prevalent chemical of the body (~ 100 M), and proton NMR requires only a low radio frequency and a moderate magnetic field for good imaging. Differences of water content of tissues can be displayed in three dimensions in a computerized tomography called zeugmatography. Excellent images can be obtained for small diameters such as the wrist, and imaging of body organs such as the heart or liver is possible. Alterations of tissue water distribution due to failure of the cell metabolism and to tissue oxygen lack in heart disease may be detectable in the 3D images, especially when the changes are enhanced by the selective infusion of paramagnetic ions. A more direct measure of cell and organ metabolism may be obtained by using slightly higher magnetic fields and radio frequencies, and observing the nuclear spins of tissue phosphate compounds such as the energy-rich CrP and ATP. In this case a direct assay of the tissue energy metabolism is obtained. While 3D imaging with phosphorus NMR may be some years in the future, the non-destructive and non-invasive assay of large unresolved portions of organs or of the extremities that lack sufficient oxygen for adequate energy metabolism would be a great boon — and a suitable example might well be studies of the brain by NMR in premature infants that are in danger of inadequate brain oxygen, and thus require precisely controlled oxygen atmospheres. Such is my personal view of new directions in biophysics and I am sure that another biophysicist would point you in other directions. But the directions are no more important than how to travel along the road to new destinations. First and foremost is the self-evident necessity for the closest interaction of the physicist, the chemist, the biologist and, in some cases, the clinician, to both experimental and theoretical problems in pure and applied Biophysics. But such interactions are facilitated by the rather rare interdisciplinary scientist who has skills, or who can readily assimilate them, in these four diverse study areas. Secondly, I suggest to the young scientists here - and we are glad you are here - that a new direction is not a substitute for good science a new idea poorly documented, a good technique poorly and unreliably executed may lead to slower scientific progress than a completed

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research. What science needs is hard work on good ideas, with reliable methods, of course, if the breakthrough is a really novel idea. Let's hear about that too! These are the roads I hope we all travel in our several directions to continue Professor Kotani's revolution! It is customary to bring some gift characteristic of the particular locale of my origin. Dr. P. L. Dutton of the Johnson Research Foundation of Medical Physics has struck off a special emblem, appropriate to this occasion, examples of which I have especially for my dear friends and colleagues Professors Kotani, Ebashi and Oosawa. The statements of this overview are based upon the works of my colleagues at the Johnson Research Foundation and elsewhere over the world. I have referred to many such works, some of which are published and some unpublished. I wish to thank my colleagues for their contributions to Biophysics that make the overview possible. Thank you, BRITTON CHANCE

Opening address by the president of IUPAB. 3 September 1978. VIth congress International Union of Pure and Applied Biophysics.

Quarterly Reviews of Biophysics II, 4 (1978), pp. 629-635 Printed in Great Britain Opening Address by the President of IUPAB 3 September 1978 V I T H...
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