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| Do physicists make better biologists? |
| An effective war on disease can only be waged if the energies of many disciplines, not just biology and medicine, are harnessed together. These allied disciplines range from mathematics, engineering, and computer sciences to sociology, anthropology, and behavioural sciences. But the weight of historical evidence and the prospects for the future place physics and chemistry most prominently among them. |
| The human body and its components are physical objects that can be viewed and measured and altered in ways that resemble what a physicist might do with any physical object. |
| There are contemporary problems in the biomedical sciences that can challenge physicists, young and old. |
| Formal training in physics can help play an active investigative role in biomedical sciences. |
| Biological forms as physical objects |
| For several hundred years physicists—and especially their principles, methods and machines—have been illuminating our views of the human body and of every other living thing. |
| Some examples of the hundreds of physics-based methods applied to view living bodies without the disruption of anatomical dissection or to visualise very small components of living things: |
| Macro-imaging: Conventional X-radiology, computerised tomography scanning, ultrasound, positron-emission tomography (PET), and magnetic resonance imaging (MRI). |
| The impact of these procedures on medical practice is unquestioned and continues to grow as new methods and new applications appear. Two recent examples convey the exciting potential for both clinical and investigative work—the use of PET to provide images of the human brain at work and the use of MRI to analyse both structural and functional characteristics of the human heart in disease states. |
| Micro-imaging: Electron microscopy, X-ray crystallography, and nuclear magnetic resonance. Sometimes a collection of methods proves important, as in the use of molecular hybridisation, fluorochrome chemistry, wave optics, and computer science in spectral karyotyping, a procedure that allows rapid identification of each of the 23 pairs of normal human chromosomes and the origins of recombined chromosomes that often appear in cancer cells. |
Physicists, the physical basis of heredity, and the rise of molecular biology Max Delbruck, a leading physicist turned biologist of the 1940s, attracted many other physicists to biology with the assistance of Niels Bohr’s book, Light and Life and Schrodinger’s book, What is Life? Leading physicist Leo Szilard, one of the converts, claimed that physicists brought to biology “not any skills acquired in physics, but rather an attitude: the conviction which few Delbruck and his converts were important, but there were, in fact, multiple intellectual lineages connected with physics that helped to create the modern world of molecular biology. For instance, Warren Weaver was a mathematical physicist turned science administrator, who, in 1932, first used the term “molecular biology”. British scientists with a strong physical bent, such as Astbury, Bragg, and others, used X-ray diffraction to study the organisation of fibres of many kinds, mainly proteins found in textiles, in an intellectual lineage that led to Wilkins and Franklin and, of course, DNA. The American geneticists, T H Morgan and H J Muller used physical agents, X rays, to induce mutations in fruit flies. |
| Some important findings that form the pillars of modern molecular biology |
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The identification of DNA as genetic material, a description of the physical organisation of DNA through X-ray crystallography |
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The deduction of the principles of base pairing and the strategy of replication from the organisation of the double helix |
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The deciphering of the genetic code as triplets chosen from a set of four nucleotides |
| Contemporary biology, especially the deciphering of genomes by nucleotide sequencing, is rapidly becoming a science that demands more intense mathematical and physical analysis than biologists have been accustomed to, and such analysis will be required to understand the workings of cells. |
| (Based on a plenary talk delivered by Harold Varmus, M.D., Director, NIH, at the centennial meeting of the American Physical Society, Atlanta, GA., US, on March 22, 1999) |
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