The study of small drug molecules interacting with nucleic acids is an area of intense research that has particular relevance in our understanding of relative mechanism in chemotherapeutic applications and the association between genetics (including sequence variation) and drug response. In this contribution, we demonstrate how the sequence-specic binding of an anticancer drug Dacarbazine (DTIC) to single base (A-G) mismatch could be sensitively detected by combining electrochemical detection with biosensing surface based on gold nanoparticles.

Dansylamide? has been modified by the introduction of several side chains into the sulfonamide substituent. Compounds with no, or with only one positive charge at the side chains were found not to be useful for association studies with nucleotides or nucleic acids. Relatively high binding constants with moderate base selectivities have been observed with a ligand obtained from dansyl chloride and N,N9-bis(3-aminopropyl)piperazine, which contains two dansyl units and two permanently charged peralkylammonium centers. Interactions of this ligand with double-stranded nucleic acids show a biphasic binding, the first at base pair concentrations below 1027 M being only detectable by a decrease of fluorescence intensity. The second phase is characterized by increased fluorescence and by wavelength changes similar to effects observed in lipophilic solvents and by affinities of up to 5×105 M. At higher concentrations bathochromic shifts and extinction changes in UV spectra of the dye suggest an intercalation mechanism, in line with preliminary circular dichroism studies.

The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.

The interaction between fl-cyclodextrin (β-CD) and riboflavin together with its electrogenerated intermediate anion radicals has been specifically investigated by in situ electrochemical UV-visible spectroscopy. It appears that the anion radicals are included more tightly than the parents and stabilized in the special microenvironment of the β-CD cavity. The utility of β-CD for probing the existence of an unstable intermediate species at the electrode is also demonstrated.