Bioeffects Of Melamine And Its Analogues On DsDNA,EcoR? And Other Nucleases

Melamine(MEL),cyanuric acid(CYA)are high-yield chemical products and raw materials.MEL and other triazine substances have come into wide use.MEL has been illegally added to infant milk powder and many dairy products and agricultural by-products,they have been sold all over the world with serious consequences.These food scandals have prompted continued global attention to the emergence of melamine in food and in natural world.Triazine such as MEL can enter the natural environment through a variety of ways.These include the using of melamine as raw materials for chemical fertilizer production;and the using of fertilizer causes MEL migrate into the soils and aquatic environment.In addition,MEL enter the food chain as metabolites of animal feed additives,pesticide and disinfectants;and migration from industrial products is also included.Facing the existence of MEL and other triazine pollutants in the environment at low doses,most of the studies focused on the acute toxicity and subacute toxicity of MEL,and fewer studies focus on the mechanism of action at molecular level.Therefore,it's necessary to study their effects at the molecular level on biological macromolecular structure,function and participation of activities.Nucleic acid is a kind of biological macromolecules that carry genetic information of living organisms and plays an important role in life.In this study,the reaction between dsDNA and nuclease was selected.The aim of this study is to understand the effect of MEL etc on the activity of nucleic acid biomolecules.MEL's ability to change the thermal differential spectra of DNA indirectly reflects that the base stacking is disturbed by MEL and that CYA&MEL can interfere with complementary double strand pairing.CYA&MEL can increase the thermal stability of dsDNA and increase the temperature of melting.There is weak interaction between MEL or CYA and DNA and does not change the superhelix state of cyclic DNA.CYA,MEL and its analogues(2,4-diamino-6-methyl-1,3,5-triazine and 2,4,6-triaminopyrimidine)mainly binds to the minor-groove region on DNA double helix.They all act on nucleic acids and proteins.When nuclease BAL-31 reacts with dsDNA,both MEL and CYA can promote the reaction.The fluorescence of BAL-31 can be quenched by CYA.The synchronous fluorescence peaks of tyrosine and tryptophan were blue-shifted under the influence of CYA,indicating the interaction between them.MEL and CYA promote the reaction of DNA with EcoR I,Nde I and Pst I nonmonotonicity.In the simulated docking results,MEL and its structural analogues,including CYA,all bind in the same position with EcoR I,and they are all close to the active sites of EcoR I;so all four small molecules may interfere with the conformation at the active sites.The results of circular dichroism showed that the interaction of MEL and other small molecules with BSA led to the unfolding of the secondary structure of peptide chain.Synchronous fluorescence experiments showed that all four small molecules could change the microenvironment of tryptophan residues on EcoR I,and 2,4,6-triamino-pyrimidine had a stronger effect on EcoR I and BSA.The type of interaction between the two proteins was hydrophobic interaction.