Determination of nanogram quantities of osmium-labeled nucleic acids by stripping (inverse) voltammetry.
Modification of nucleic acids with OSO4 in the presence of pyridine results in a formation of a covalently bound electroactive center in a polynucleotide chain detectable by polarographic (voltammetric) methods. It has been shown that DNA modified with osmium (DNA-Os) accumulates at the hanging mercury-drop electrode during a waiting time in a wide range of potentials between 0 and -1.0 V (against the saturated calomel electrode) and produce at neutral pH a well-developed reduction peak at about -1.2 V due to scanning in the cathodic direction. Using the differential-pulse stripping (inverse) voltammetry, nanogram quantities of single-stranded DNA-Os can be determined at relatively short waiting times (1-3 min). Double-stranded DNA is modified with osmium to a much lesser extent as compared to single-stranded polynucleotides. The degree of modification of double-helical DNA is influenced by the presence of single-stranded and distorted double-stranded regions in the DNA molecules and by the environmental conditions which influence the DNA conformation. Osmium can thus be used as a probe of the DNA structure, and a few micrograms of double-helical DNA sample suffice for the voltammetric analysis.
D000818:Animals; D002417:Cattle; D004247:DNA / Q000032:analysis*; D004277:DNA, Single-Stranded / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009992:Osmium; D009993:Osmium Tetroxide; D010084:Oxidation-Reduction; D010957:Plasmids; D011048:Polarography
D004277:DNA, Single-Stranded; D009992:Osmium; D004247:DNA; D009993:Osmium Tetroxide