Nucleic acids osmium tetroxide

Miscellaneous. Aside from the oxidation chemistry described, only a few catalytic applications are reported, including hydrogenation of olefins (114,115), a, [3-unsaturated carbonyl compounds (116), and carbon monoxide (117) and the water gas shift reaction (118). This is so owing to the kinetic inertness of osmium complexes. A 1% by weight osmium tetroxide solution is used as a biological stain, particulady for preparation of samples for electron microscopy. In the presence of pyridine or other heterocyclic amines it is used as a selective reagent for single-stranded or open-form B-DNA (119) (see Nucleic acids). Osmium tetroxide has also been used as an indicator for unsaturated fats in animal tissue. Osmium tetroxide has seen limited if controversial use in the treatment of arthritis (120,121). 

Oxidation specifically attacks thymine (57,58) and is applicable to all nucleic acid analytes. This strategy aims to either eliminate or alter thymine and thymine like-moieties for better analyte recognition. Oxidation with osmium tetroxide (5% OSO4) occurs at 300 pg/ml, with nucleic acids or DNA (plasmid) in 100 mM NaCl, 10 mM Tris (pH 7.6) and 1 mM EDTA. Incubation is at 70 C for 90 minutes. Standard ethanol extraction follows, with resuspension in tm-EDTA buffer. A series of chromatograms, including thymine altered by ozone and osmium are in press. 

The immunosuppressant activity of cisplatin, as with most antitumour agents which inhibit nucleic acid synthesis, suggests application in alteration of the immune system associated with arthritis, and platinum complexes have been shown to improve some signs of inflammation [103, 104], Osmium tetroxide, as an intraarticular injection, is essentially of historical interest [105,106],... 

FIGURE 1.8 Some chemical reactions of bases and nucleotides, (a) Hydrolysis of a dinucleotide by alkali. Bases are denoted by B1 and B2. R denotes ribose or deoxyribose. (b to k) Chemical reactions (b) bisulfite, (c) chloroacetaldehyde, (d) diethyl pyrocarbonate, (e) dimethyl sulfate, (f) formaldehyde, (g) glyoxal, (h) hydrazine, (i) nitric acid, (j) nitrous acid, and (k) osmium tetroxide. Partly from R. L. P. Adams, J. P. Knowler, and D. P. Leader (1986). In The Biochemistry of the Nucleic Acids, 10th ed., pp. 5—34. Chapman Hall, with permission. 

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