Freeze-Etching Electron Microscopy: Recent Developments and Application to the Study of Biological Membranes and Their Components

1985 ◽  
pp. 55-71 ◽  
Author(s):  
T. Gulik-Krzywicki
Keyword(s):  
Electron Microscopy ◽  
Biological Membranes ◽  
Recent Developments ◽  
Freeze Etching

scholarly journals Fracture faces of frozen membranes: 50th anniversary

2016 ◽  
Vol 27 (3) ◽  
pp. 421-423
Author(s):  
Daniel Branton
Keyword(s):  
Electron Microscopy ◽  
Lipid Bilayers ◽  
Fracture Process ◽  
Relative Proportion ◽  
50Th Anniversary ◽  
Biological Membranes ◽  
Bilayer Membrane ◽  
Biological Cells ◽  
Membrane Surfaces ◽  
Freeze Etching

In 1961, the development of an improved freeze-etching (FE) procedure to prepare rapidly frozen biological cells or tissues for electron microscopy raised two important questions. How does a frozen cell membrane fracture? What do the extensive face views of the cell’s membranes exposed by the fracture process of FE tell us about the overall structure of biological membranes? I discovered that all frozen membranes tend to split along weakly bonded lipid bilayers. Consequently, the fracture process exposes internal membrane faces rather than either of the membrane’s two external surfaces. During etching, when ice is allowed to sublime after fracturing, limited regions of the actual membrane surfaces are revealed. Examination of the fractured faces and etched surfaces provided strong evidence that biological membranes are organized as lipid bilayers with some proteins on the surface and other proteins extending through the bilayer. Membrane splitting made it possible for electron microscopy to show the relative proportion of a membrane’s area that exists in either of these two organizational modes.

Freeze-etching studies of membrane structure

1971 ◽  
Vol 261 (837) ◽  
pp. 133-138 ◽  
Keyword(s):  
Electron Microscopy ◽  
Fatty Acids ◽  
Membrane Structure ◽  
Molecular Model ◽  
Biological Membrane ◽  
Biological Membranes ◽  
Thin Sections ◽  
Polar Groups ◽  
Freeze Etching ◽  
Made In

Thin sections of biological membranes examined by electron microscopy appear as two dark lines separated by a lighter space. This observation, first made in the 1950s, has been interpreted as confirmation of the Danielli-Davson model of the biological membrane (Robertson 1959) . Proponents of this interpretation have equated the dark lines to proteins and other polar groups in the membrane and the intervening light space to the lipid fatty acids (Stoeckenius 1960) . However, it has become clear that other interpretations are possible (Korn 1966; Branton & Park 1968) and that the electron microscope observations do not in fact prove the validity of any one molecular model of the biological membrane (Stoeckenius & Engelman 1969). During the last few years a number of biochemical and physical probes have given us more direct information regarding the composition and molecular configurations within biological membranes.

Freeze-Fracture Replication of Frozen Outer Segments of Rat Retinal Rods

1969 ◽  
Vol 27 ◽  
pp. 392-393
Author(s):  
Thomas S. Leeson ◽  
C. Roland Leeson
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Outer Segment ◽  
Freeze Fracture ◽  
X Ray Diffraction ◽  
X Ray ◽  
Outer Segments ◽  
Retinal Rods ◽  
Temperature Electron ◽  
Freeze Etching

Numerous previous studies of outer segments of retinal receptors have demonstrated a complex internal structure of a series of transversely orientated membranous lamellae, discs, or saccules. In cones, these lamellae probably are invaginations of the covering plasma membrane. In rods, however, they appear to be isolated and separate discs although some authors report interconnections and some continuities with the surface near the base of the outer segment, i.e. toward the inner segment. In some species, variations have been reported, such as longitudinally orientated lamellae and lamellar whorls. In cross section, the discs or saccules show one or more incisures. The saccules probably contain photolabile pigment, with resulting potentials after dipole formation during bleaching of pigment. Continuity between the lamina of rod saccules and extracellular space may be necessary for the detection of dipoles, although such continuity usually is not found by electron microscopy. Particles on the membranes have been found by low angle X-ray diffraction, by low temperature electron microscopy and by freeze-etching techniques.

Chloroplast division in spinach leaves examined by scanning electron microscopy and freeze-etching

1980 ◽  
Vol 46 (1) ◽  
pp. 87-96
Author(s):  
N. Chaly ◽  
J.V. Possingham ◽  
W.W. Thomson
Keyword(s):  
Electron Microscopy ◽  
Green Light ◽  
Cell Area ◽  
Low Intensity ◽  
Spinach Leaf ◽  
Freeze Etching ◽  
Leaf Disks ◽  
Scanning Electron ◽  
Spinach Leaves

Spinach leaf disks were cultured for 5 days in low-intensity green light and then were transferred to high-intensity white light. Harvests over the next 16 h established that cell area increased by about 80% and chloroplast number per cell increased by about 65%, while the percentage of dumbbell-shaped chloroplasts per cell decreased by 65%. Freeze-etch replicas of fixed and unfixed leaf disks, as well as scanning electron-microscope preparations of fixed material, contained dumbbell-shaped chloroplasts constricted to various degrees. Freeze-etch replicas of unfixed cells from young leaf bases, in which the number of chloroplasts per cell is known to be rapidly increasing, also contained many constricted chloroplasts. It is concluded that dumbbell-shaped chloroplasts occur in vivo and represent a stage in the division of chloroplasts.

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