Study Of The Interactions Between Three Effective Components Of Three Kinds Of Chinese Herbs With DNA

The nature and dynamics of binding small molecules to biopolymers represents an area of active investigation. Studies directed toward the design of site- and conformation-specific reagents provided routes toward rational drug design as well as a means to develop sensitive chemical probes of polymer structure. Deoxyribonucleic acid (DNA) is a kind of key biologic large molecule, it plays very important role in life genetic code' interpretation, transcription and copy, it is the primary target molecule for most of anticancer and antiviral therapies according to the cell biology. The investigation of interaction of DNA with other molecules is of great importance in elucidating the structure of DNA and their functions. It is also helpful to understand some diseases and the mechanism by which some medicines (especially antitumor drugs) act. In this thesis the results of interaction of some antitumor compounds with DNA were reported.This thesis consists of three sections as follows:First, resonance light scattering spectra and UV-VIS spectra were used to study the interaction of borneol with DNA. The results indicate that the addition of DNA can increase RLS intensity of borneol at 410 and 470 nm under a physiological condition (pH=7. 40 and t=37°C), which may be one of the reasons why borneol can be one of antibacterial Chinese medicines. UV-VIS spectra showed that there appear two iso-absorptive points and a red shift of 4.0 nm, which means that borneol intercalates into the double helix of DNA. Ionic strength and pH of reaction system were changed to investigate the influencing factors. It is showed that reaction system of borneol-DNA is sensitive to increasing ionic strength and changing pH. The above results suggested that borneol binds to DNA via a weak partial intercalation, revealed by competitive and viscosity experiments. The additional sequence of reagents has little effect on RLS and Absorption intensity, and calibration graphs and linear rangewere determined under the optimal conditions.Second, the interaction of eugenol and DNA in Tris-HCl buffer solution (pH7. 40) and under low ionic strength (less than 0. 0035mol/L) was investigated by scattering spectrum. Results showed that long range assembly of three enhanced resonance light-scattering (RLS) peaks appear at 420 > 455> 470 nm. The RLS intensity can be increased in linear relationship with the increasing of DNA concentration. UV-VIS spectra were surveyed to gain more information of the mode of eugenol with DNA. Two iso-absorptive points were observed at 255 and 317 nm. Results showed that a new complex is produced and eugenol can interfere with the replication of DNA. The influencing factors and the optimum reaction conditions have been determined. The additional sequence of reagents has little effect on reaction system. As an effective ingredient of high antibacterial coefficient, eugenol can react on DNA easier and more efficient, and reaction system was steadier than borneol.Third, emission spectra, absorption spectra and viscosimetric studies have been carried out on the interaction of emodin with calf thymus DNA. Results showed that, under pH7. 40, in the presence of DNA the system of emodin-DNA exhibited a large decrease in emission spectra. A hypochromic effect at 424 nm, a red shift of 5. 0 nm and two iso-absorptive points were observed in the UV-VIS spectra, which suggested that emodin binds to DNA via an intercalation mode. Competitive experiments and viscosity studies were carried out for the further research. The fluorescence quenching data were plotted according to the Stern-Volmer equation. Ksv and Ksv were quenching constants in the absence and in the presence of DNA, respectively. Results showed that Ksv / Ksv =0. 73. In the presence of DNA, the effect of I on fluorescence intensity becomes smaller than that of emodin in the absence of DNA, which also proved that emodin react on DNA by an intercalation mode.