Detection of DNA segment utilizing an immobilized DNA electrode and an osmium complex

The interactions of an osmium complex with immobilized dsDNA and ssDNA electrodes were studied by linear sweep voltammetry. The appearance of an oxidation peak of the complex indicated that the osmium complex specifically interacted with dsDNA. The osmium complex was concluded to interact electrostatically with phosphate groups, and nonelectrostatically with base pairs and/or the sugar backbone. Recognition of DNA sequences by the osmium complex was examined. The immobilized ssDNA electrode was hybridized with probes, and then the charge of DNA hybrids were measured in phosphate buffer (pH 7.0). After interaction of this electrode with the osmium complex, the charge of the complex was measured in phosphate buffer (pH 7.0). Results showed that complementary probes of more than 12 mers were recognized by the osmium complex, and so that the osmium complex binds to major or minor grooves of the DNA helix.