Study On The Interaction Properties Of Chitin Synthesis Inhibitor With Calf Thymus DNA

Along with the development of modern agriculture,the problems aroused from the residue of pesticides are getting more and more serious.Chitin synthetic inhibitors,one of effective and low-toxic pesticide,have been widely used and detected in soil,water,sediment and crops,due to their hydrophobicity and persistence.It has been proved that they could enrich in the food chain through various routes and lead to the adverse genetic effects of non-target organisms.DNA,as an important genetic material of organisms,may be damaged by exogenous compounds and produce a serious of adverse effects such as gene mutation,chromosome aberration,and strand breakage.Because that the change of DNA may causes significant impacts on organisms,it is of great significant to study the interaction between chitin synthetic inhibitors and DNA.In this study,we used UV-vis absorption spectroscopy and fluorescent spectroscopy to investigate the interaction between calf thymus DNA and the Chitin synthetic inhibitors in vitro.The selected pesticides included diflubenzuron,teflubenzuron,bistrifluron,hexaflumuron,lufenuron,novaluron,chlorflua-zuron,flufenxuron and buprofezin.The interaction mode and the type of binding force among them were firstly studied.The binding constants and the number of binding sites were calculated as well.Then the relationship between the structure of pesticides and its binding to DNA at molecular level was analyzed.The results provided experimental theoretical basis for the risk assessment of non-target genetic toxicity.The main contents and results are as follows:?1?The interaction between eight benzoylurea insecticides and ctDNA was investigated by UV-vis absorption spectroscopy and fluorescent spectroscopy at pH 7.4 under physiological conditions.It is found that the binding ability of pesticides declined with the increase of the length of the substituent on the N-phenyl aromatic ring.In brief,the pesticides substitutedby chlorine and fluorine have the best binding capacity.The pesticides substituted by Chlorofluoro-alkoxy follows it.And the pesticides substituted by Chlorofluoro-phenoxy are the last one.It is also found that the interaction between benzoylurea insecticides and ct DNA mainly depends on hydrogen bonds and Vander Waals forces by calculating the thermodynamic parameters of the interaction between the pesticides and ctDNA.?2?The binding mode of eight pesticides with ctDNA were researched by DNA melting point,KI quenching experiment and salt effect experiment.The results showed that the binding of diflubenzuron,teflubenzuron and hexaflumuron to ctDNA was an intercalative mode.Novaluron and flufenxuron bind to ct DNA in a grooveing mode and lufenuron binds to ct DNA in an electrostatic interaction.Bistrifluron binds to ct DNA with intercalative effect and grooveing mode.Chlorfluazuron binds to ctDNA in grooveing mode and electrostatic interaction.?3?The methylene blue?MB?was used as DNA probe to investigate the interaction between buprofezin and ctDNA and the influence of heavy metals(Cd²⁺,Co²⁺,Cu²⁺and Ni²⁺)on their binding properties.The results showed that buprofezin binds to ct DNA in an intercalative mode.The presence of metal ions did not change the interaction mode between buprofezin and ct DNA,but influenced the binding intensity of buprofezin to ct DNA.A small quantity of Cu²⁺ and Ni²⁺ showed a promotion between buprofezin and ct DNA via an ionic-bridge mechanism,but a large quantity of ions would modify the structure of ctDNA and weaken the binding capacity.Meanwhile,Co²⁺ and Cd²⁺ could penetrate the ctDNA and competitively bind to ctDNA,resulting in the declination of binding constant.