The Influence Of Surfactants On The Interaction Between Drugs And Nucleic Acid

The interaction of vitamin B₂ (VB₂) with single stranded DNA (ssDNA) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the reaction of VB₂ at the glassy carbon electrode is a quasi-reversible process. With the addition of ssDNA into VB₂ solution, the oxidation peak and the reduction peak currents(ip) of VB2 both decrease, and the oxidation peak potential shifts negatively whereas the reduction peak potential shifts positively. With the increasing ssDNA concentration, the oxidation peak current of VB₂ decreases. With the increase of pH value of the system, both peaks of VB₂ shift negatively and linearly. The reaction of VB₂ at ssDNA modified GCE is a absoption-controlled quasi-reversible process. The decrease of i_p value and the peak potential shift of both peaks of VB₂ at a ssDNA modified GCE were more significant than that at a bare GCE. Furthermore, VB₂ and ssDNA forms a 1:1 type supermolecular complex, which is similar to the interaction of VB₂ with double stranded DNA (dsDNA). The results above will provide theoretical basis for understanding the interaction of denatured DNA with drugs and the repair of denatured DNA.The effects of cationic surfactants, cetyltrimethylammonium bromide (CTAB) and dodecyltrimethyl ammonium bromide (DTAB), on the interaction of thionin with DNA were investigated by UV-vis spectroscopy, fluorescence spectroscopy, conductivity and freeze-fracture etching method. The results show that thionin interacts with DNA mostly by intercalation in addition to static interaction of thionin, and that they form a new complex (DNA-TH_n). The intercalation of thionin into G-C rich region of DNA facilitates the fast electron tranfer between Guanine (G) and singe excited state of thionin, making the fluorescence of thionin quench with the apparent quenching coefficient of 4.54x10³ L/(mol s). The addition of cationic surfactant weakens thehypochromic and red-shift effect of the system, which indicates that cationic surfactants inhibit the intercalation of thionin into the DNA strands, and that the inhibition becomes stronger with the increasing concentration and chain length of the surfactants. The inhibition can be ascribed to the change of DNA conformation induced by cationic surfactants. The freeze fracture transmission electron micrographes of the systems show that the conformation of DNA changes from supercoiled state to global state with the addition of cationic surfactants, which confirms the above spectral explanation. The results above will provide guidance for the effective control of the interaction of drugs and DNA.The effects of anionic surfactants, sodium dodecyl phosphate (SDS), on the interaction of thionin with DNA were investigated by UV-vis spectroscopy. The results show that negatively-charged SDS combines with positively-charged thionin and forms H-type and J-type aggregates. With the addition of anionic surfactant SDS into the thionin-DNA system, the absoption intensity of thionin monomer increases rather than decreases, which indicates that the formation of thionin-SDS complex hinders the intercalation of thionin into the DNA strands due to the larger spatial effect. The results above will provide further guidance for the effective control of the interaction of drugs and DNA.