Laue method

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The Laue method (also known as Laue diffraction ) is a method for crystal structure analysis . It is named after the German physicist Max von Laue and was carried out for the first time in 1912 by Walter Friedrich and Paul Knipping . Historically, it is the oldest method of X-ray diffraction and thus substantiates Laue's theory.

description

Basic sketch of the structure

In the Laue method, a single crystal is used to diffract the X-rays . Point-like reflections can be seen on the photographic film placed behind it . This differs from the Debye-Scherrer method , for example , in which the X-rays are diffracted by many small crystals of a crystal powder and continuous diffraction lines or circles can be seen.

In the Laue process so-called white, non-monochromatic X-rays ( bremsstrahlung ) are used. This means that several grating layers simultaneously meet the diffraction condition (see Bragg equation and Laue condition ). The Laue method is therefore much faster than the diffraction with monochromatic X-ray radiation used in other methods , which therefore only has a discrete or line spectrum of a certain wavelength .

The Laue method can therefore also be used to follow dynamic processes in crystals. In the case of protein crystals in particular , (dynamic) changes in the protein structure in the crystal can be observed and conclusions can be drawn about how the proteins function. The disadvantage, however, is that you don't know which reflex originates from which wavelength ( indexing problem ). In addition, many reflexes occur at the same time, so they often overlap with each other. While the experiment of the Laue method is very fast, the subsequent data processing is very difficult and time-consuming.

literature

  • W. Friedrich, P. Knipping, M. von Laue: Interference phenomena in X-rays . In: Bavarian Academy of Sciences, meeting reports . 1913, p. 303-322 , doi : 10.1002 / andp.19133461004 . W. Friedrich, P. Knipping, M. von Laue: Interference phenomena in X-rays . In: M. von Laue (Ed.): Collected writings and lectures . tape
     I. . Friedr. Vieweg & Son., 1961, p. 183-207 .
  • Jose Luis Amoros, MJ Buerger , MC Amoros: Laue Method . Cambridge University Press, Cambridge 1975, ISBN 0-12-057450-0 .
  • JR Helliwell: Macromolecular crystallography with synchrotron radiation . Academic Press, New York 2005, ISBN 0-521-54404-1 .
  • JJ Rousseau: Cristallographie geométrique et radiocristallographie . Masson, 1995, ISBN 2-225-84990-0 , Chapter 11: "Diagrams de Laue".