Trade in Services for Growth and Structural Transformation in West Africa

The structure of pre-mRNA and mRNA from erythroid cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082030 ◽

1978 ◽

Vol 36 (2) ◽

pp. 234-235

Author(s):

A.-M. Ladhoff ◽

B.J. Thiele ◽

Ch. Coutelle ◽

S. Rosenthal

Keyword(s):

Bone Marrow ◽

Structural Transformation ◽

Electron Micrographs ◽

Ammonium Acetate ◽

Bone Marrow Cells ◽

Erythroid Cells ◽

Globin Mrna ◽

Ordered Structures ◽

Rabbit Bone ◽

Rabbit Reticulocytes

The suggested precursor-product relationship between the nuclear pre-mRNA and the cytoplasmic mRNA has created increased interest also in the structure of these RNA species. Previously we have been published electron micrographs of individual pre-mRNA molecules from erythroid cells. An intersting observation was the appearance of a contour, probably corresponding to higher ordered structures, on one end of 10 % of the pre-mRNA molecules from erythroid rabbit bone marrow cells (Fig. 1A). A virtual similar contour was observed in molecules of 9S globin mRNA from rabbit reticulocytes (Fig. 1B). A structural transformation in a linear contour occurs if the RNA is heated for 10 min to 90°C in the presence of 80 % formamide. This structural transformation is reversible when the denatured RNA is precipitated and redissolved in 0.2 M ammonium acetate.

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Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179014 ◽

1990 ◽

Vol 48 (1) ◽

pp. 52-53 ◽

Cited By ~ 1

Author(s):

Jean-Luc Rouvière ◽

Alain Bourret

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Grain Boundary ◽

Structural Transformation ◽

Mirror Symmetry ◽

High Resolution Electron Microscopy ◽

Structural Transformations ◽

Covalent Bonds ◽

Resolution Electron ◽

Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

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