Study On The Interaction Mechanism Of Drug And Pesticide With DNA By Electrochemistry And Spectrometry Techniques

This thesis is divided into five parts. The research actuality of interaction between small molecules with DNA in recent years has been reviewed and the binding modes between some clinical drugs and pesticide with DNA were studied. The application of chemometrics in analysis of two-dimensional and three-dimensional data also had been developed. And the application of chemometrics in complicated biochemical system (probe-DNA-small molecular) can solve some problems and obtain the equilibrium concentration and pure spectra of each component.In part one, the chemical and biological characters of DNA were introduced simply first, then the research methods, research objects and binding modes of interaction between small molecules and DNA were reviewed in turns. DNA is the basic genetic material of all organisms and the main target of some drugs in the organism, and study on it has become an important research field of life science. Along with more attention has been given on the research of the interaction between DNA and small molecules, the mechanisms of the action of some drugs and origins of some diseases have generally been understood. Moreover, the investigation based on DNA interactions with small molecular compounds also has great significance to design new DNA-targeted drugs and to screen these drugs in vitro. At last, the development trend was forecasted and exploiting new probes, using various techniques simultaneously and the use of chemometrics were chosen as the emphasis of this thesis.In part two, the interaction between riboflavin (VB₂) and DNA was studied by using cyclic voltammetry, differential pulse voltammetry, ultraviolet spectrophotometry and fluorescence spectrometry. Neutral red also was used as electrochemical probe in this article. The results of these methods (The peak current of riboflavin decreased and the peak potential shifted positively, the UV spectrum produced hypochromic effect, the fluorescence of riboflavin had quenching effect with increasing the concentration of DNA and the competition between riboflavin and neutral red interacted with DNA) can come to a conclusion: riboflavin binds to calf thymus DNA mainly by intercalation. Information such as intrinsic binding constant and binding numbers of riboflavin per DNA also was obtained through numerous calculations simultaneously, the result is approximate and believable.In part three, the interaction of quercetin-Cu²⁺ complex with calf thymus DNA was investigated with Neutral Red (NR) as a probe and using UV-visible spectrophotometry, cyclic voltammetry and synchronous fluorescence spectroscopy. These methods are simple, convenient and reliable. The results showed that both quercetin-Cu²⁺ complex and NR molecule can intercalate into the double helix layer of DNA, and there was a competition between these two interactions. Information such as intrinsic binding constant (K=1.82×10⁵ M^-1 and ratio (K_r/K_O) of binding constants for the reduced and oxidized forms of a bound species and interaction mode was obtained. Furthermore, a chemometrics approach, alternative least squares (ALS) algorithm, was used to resolve the measured complex two-way array absorption spectral data and the equilibrium concentration profiles of each component in the reaction as well as the corresponding pure spectra were obtained. The ALS analysis showed that the intercalation of quercetin-Cu²⁺ complex molecule into DNA proceeds by exchanging with NR probe, and can be attributed to two parallel reactions.