Freeze etching technology

from Wikipedia, the free encyclopedia

The freeze-etching technique (syn. Freeze fracture technique ) is a process for the production of electron microscopic preparations . It is mainly used to examine the membrane structures in cells . The basis of our modern conception of cell membranes is the concept of the lipid bilayer by Gorter and Grendel. The Danielli-Davson-Robertson model of the lipid double layer supplements the original concept with the assumption that the membranes contain proteins. This additional assumption explains the low measured surface tension of real biological membranes in contrast to the model calculations based on the assumption of Gorter and Grendel. Robertson coined the term “standard membrane”, which is still used today. Experimental evidence for the existence of the bilayer has been provided by various methods.

The freeze fracture techniques are believed to be the surest clue to the adoption of Robertson's unitary membrane. Cell components or model membranes are very quickly frozen, broken and then etched by sublimating the ice. In order to make the samples visible in the scanning electron microscope , they are then vaporized with a heavy metal and the wafer-thin metal film is displayed like a surface imprint in the microscope. Since with the freeze fracture technique the membranes are partially split in their inner plane, the images obtained show the intra- and extracellular parts of the membrane and their respective protein components. On the basis of the data obtained by this method, the model of Robertson's unit membrane could be confirmed and extended by Singer and Nicolson by the so-called fluid mosaic model.

The technology was developed in the 1960s by Kurt Mühlethaler and Hans J. Moor at the ETH Zurich.

literature

  • CE Hall: Introduction to Electron Microscopy . McGraw-Hill, New York 1966.
  • L. Reimer: Electron microscopic examination and preparation techniques . Springer, Berlin 1967.
  • HE Huxley, A. Klug: New Developments in Electron Microscopy. Royal Society, London 1971.
  • RG Kessel, CY Shih: Scanning Electron Microscopy in Biology. Berlin 1974.

Web links

Individual evidence

  1. ^ JF Danielli et al .: A contribution to the theory of permeability of thin films . J. Cell Physiol. 5: 495-508. (1935).
  2. ^ E. Gorter, F. Grendel: On bimolecular Layers of lipoid on the chromocytes of the blood. J. Exp. Med. 41, 439-443. (1925). [1]
  3. ^ JD Robertson: The infrastructure of cell membranes and their derivatives. Biochem. Symp. 16, 3-43 (1959).
  4. ^ JD Robertson .: The molecular structure and contact relationships of cell membranes Progr. Biophys. 10, 344-418 (1960) PMID 13742209 .
  5. ^ SJ Singer, GL Nicolson: The fluid mosaic model of the structure of cell membranes. Science 175: 720-731 (1972). PMID 4333397