PMID: 6537362Apr 1, 1984Paper

Osmium-induced alteration in DNA structure

General Physiology and Biophysics
E LukásováE Palecek

Abstract

In the presence of pyridine and other ligands osmium tetroxide binds covalently to pyrimidine bases in DNA. Properties of osmium-modified native and denatured calf thymus DNA, and plasmid Co1E1 DNA were investigated by means of differential pulse polarography, absorption spectrophotometry, circular dichroism, agarose gel electrophoresis, and nuclease S1 digestion. A great difference in the reaction kinetics of native and denatured DNAs with osmium, pyridine was observed. On the ground of the slow stepwise reaction kinetics of native DNA in the initial stage of its modification by osmium it has been suggested that the primary reaction sites do not include bases contained in the intact double helix. Osmium binding to sporadic primary reaction sites (represented e.g. by bases in the vicinity of a single-strand break) in native calf thymus DNA resulted in local changes in DNA conformation limited to a close neighbourhood of the binding site. At higher osmium/nucleotide ratios disordering of the DNA structure over a region extending beyond the immediate binding site was observed. With denatured DNA the same type of structure disordering was detected already in the initial stage of the reaction at osmium/nucleotide ratios as low as 0...Continue Reading

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