KLUG, Sir Aaron
Nature, 217, 130-34, 1968.
Klug and deRosier invented methods for two-dimensional and three-dimensional digital image processing of electron microscope images. The latter method provided the theory behind the development of computed tomography (CT) by Hounsfield in the early 1970s. Hounsfield's invention of CT in the early 1970s benefited from several discussions with Klug about digital imaging (personal communication from Klug to Jeremy Norman). Hounsfield received a share of the 1979 Nobel Prize in physiology/medicine for his invention of CT, which provided the first means for visualizing, in three dimensions, virtually all types of tissue within the body (see GM 2700.4 and Grolier Medical Hundred 100). Klug received the Nobel Prize for chemistry in 1982 "for his development of crystallographic electron microscopy and his structural elucidation of biologically important nucleic acid-protein complexes." A press release written at the time refers to Klug's two- and three-dimensional imaging methods as an important part of his work: "Electron microscopy has long been used to obtain a two-dimensional picture of biological objects. The power of the method to give a clear picture of the structure is, however, limited by several factors. The molecules of life consist mainly of light atoms, which makes the picture lacking in contrast. Increased contrast can be achieved with long exposure times, but this entails the danger that the structure is destroyed by radiation damage. Instead the contrast is generally improved by "staining" with heavy metals, which can also lead to a distortion of the structure. Klug has shown that pictures of biological objects seemingly lacking in contrast often contain a large amount of structural information, which can be made available by a mathematical manipulation of the original picture. His method allows electron microscope pictures of high quality to be obtained with very low radiation doses and without the use of heavy metal stains. In this way changes in the sample are minimized, so that the electron microscope picture at high resolution is a true representation of the original biological structure. The method gives a two-dimensional projection of the sample only, but Klug has shown that a three-dimensional reconstruction of the object can be obtained by collecting pictures in several different directions of projection" (Nobel e-museum).
Subjects: BIOLOGY › MOLECULAR BIOLOGY › Genomics, IMAGING
EMBO Journal, 4, 1609-1614, 1985.
Discovery of Zinc fingers, a protein structural motif. "Zinc fingers were first identified in a study of transcription in the African clawed frog, Xenopus laevis in the laboratory of Aaron Klug. A study of the transcription of a particular RNA sequence revealed that the binding strength of a small transcription factor (transcription factor IIIA; TFIIIA) was due to the presence of zinc-coordinating finger-like structures. Amino acid sequencing of TFIIIA revealed nine tandem sequences of 30 amino acids, including two invariant pairs of cysteine and histidine residues. Extended x-ray absorption fine structure confirmed the identity of the zinc ligands: two cysteines and two histidines. The DNA-binding loop formed by the coordination of these ligands by zinc were thought to resemble fingers, hence the name" (Wikipedia article on Zinc finger, accessed 7-22).
Subjects: BIOLOGY › MOLECULAR BIOLOGY › Protein Structure