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Klug, Sir Aaron

viruses ray methods tmv

(1926– ) South African–British biophysicist: developed crystallographic electron microscopy and applied it to viruses and other nucleic acid-protein complexes.

Klug was born in Lithuania but, aged two, he moved with his parents to South Africa. Planning to graduate in medicine he took the premedical course at Witwatersrand, but found the science components attracted him enough to drop medicine and take a science degree. This was followed by research in X-ray crystallography at Cape Town and then a move to Cambridge with the intention of using X-ray methods in biophysics; but this unit was full and Klug was deflected to theoretical work in metallurgy. However, this gained him his PhD and made him familiar with computing, and the concepts of nucleation and growth within cooling metals later proved useful in his work on viruses.

In 1953 by a move to London he achieved his desire to work in biophysics. There he met Rosalind , whose X-ray diffraction pictures of crystals of tobacco mosaic virus (TMV) fascinated him; he was able to interpret the curious curved layer lines in these pictures as due to helical molecular shapes with irregular parameters. After her death in 1958 he continued working on TMV and on spherical viruses and in 1962 he joined the strong X-ray group led by at the MRC lab in Cambridge. There he devised mathematical methods for extracting more information on the structure of viruses than had been obtained previously. Viruses are composed of a nucleic acid linked with a protein: these being made mainly of light atoms (C, H, O, N), they give X-ray patterns and electron micrographs of rather low contrast. Klug’s methods used with a combination of these techniques enhanced the images, and gave a three-dimensional picture of the structure. He found that TMV has a nucleic acid chain of helical form wrapped by protein molecules; and he went on to apply similar methods to other viruses and to the bigger DNA–protein complex found in cell nuclei, chromatin, threads of which condense to become a chromosome during cell division. Klug was awarded the Nobel Prize for chemistry in 1982.

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