Osmium ammine

Fig. 3. (A) Stereo pair of starfish sperm chromatin fibers stained with osmium ammine-B. Bracket indicates the fine deposition of stain on nucleosomes and linker DNA. Arrowheads indicate where fibers enter and exit the plane of the section, and asterisks indicate sharp bends in the fibre axis. (B) Stereo pair of a reconstructed volume of a starfish sperm head by EM tomography. Axes of some fibers have been marked. Arrowhead indicates where individual fibers cannot be distinguished (from Ref. [27]). Scale bar 100 nm.

Ammonia forms a number of complexes with osmium (see Table 5), though the only fully established unsubstituted osmium ammine which has been isolated is the hexaammine [Os(NH3)6]3+ there is, however, electrochemical evidence for the existence both of [Os(NH3)6]2+ and of [Os(NH3)6]4+. Amongst the substituted ammines which have been isolated and characterized are several of osmium(II), all with supporting (or stabilizing) ir-acceptor ligands, e.g. [Os(N-H3)sCO]2 [Os(NH3)s(NO)]3+ and [Os(NH3)5(N2)]2+. 

Significantly, all three of these DNA-specific staining protocols have pictures of intranuclear DNA distribution very similar to that obtained by prior detergent premeabilization in appropriate isolation buffers (Belmont etal., 1989)—namely, the absence of DNA stain from the euchromatic compartment, and the packaging of most DNA within condensed structures well above the 30-nm chromatin fiber size. More impressively, both the osmium ammine and the chemical pretreatment (NAMA-Ur) methods have the sensitivity to detect mitochondrial and viral DNA... 

Derenzini. M.. and Farabegoli, F. (1990). Selective training of nucleic acids by osmium-ammine complex in thin sections from Lowicryl-embedded samples. J. Histochem. Cytochem. 38, 1405. 

Mikhaylova, V. T., and Markov, D. V. (1994). An alternative method for preparation of Schiff-like reagent from osmium-ammine complex for selective staining of DNA on thin Lowicryl sections. J. Histochem. Cytochem. 42, 1643-1649. 

Woodcock, C. L., Horowitz, R. A., Bazett-Jones, D. P., and Olins, A. L. (1990). Localization of DNA in chromatin using electron spectroscopic imaging and osmium-ammine staining. Proc. Int. Congr. Electron Microsc., 12th, Seattle, WA, 1990, pp. 116-117. 

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