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.

本文研究了银电极上次黄嘌呤的电化学特性。在含次黄嘌呤的醋酸～醋酸钠缓冲溶液中（pH317），在01350V电位区间内，银电极上出现一个还原峰，扫速50mV/s时，其峰电位约在0115V。该电极过程为单电子单质子过程。电化学和光谱电化学结果表明：这是由于次黄嘌呤与银形成难溶性化合物吸附于银电极表面而造成的。实验测得此难溶化合物的组成为1∶1，其溶度积为3110×10-7。用DPSV作阴极溶出分析，峰电流与次黄嘌呤浓度在810×10-71.0×10-4mol/L范围内呈良好的线性关系，此法可用于嘌呤类碱基的测定。

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.

A series of new dansylamide derivatives have been synthesized and the specific binding affinity of such fluorophores to nucleic acids has been investigated by using absorption, circular dichroism (CD), fluorescence and atomic force microscopy (AFM). The results indicate that the positive charge of the ligand and the π-π stacking between the dansyl part of the ligand and the DNA base pair may play an important role when binding to polynucleotides.

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.