Studies On The Catalytic Function Of Oxytricha G-quadruplex DNA

We have known that the various catalytic function of enzymes mainly depend on proteins in-vivo,later the scientists have discovered RNA(Ribonucleic acid)also has catalytic function.With the development of research,an increasing number of attempts has carried out whether DNA(deoxyribonucleic acid)possesses catalysis.But so far,in addition to artificial synthetic DNA,scientists have not found the presence of natural DNA has catalytic activities.However,studies have found that although it can't act as the catalyst,DNA was able to participate in many reactions and contribute to the reactions.For example,in recent years chemists have found double-stranded DNA(dsDNA)can be assembled with Cu2+ ion and catalyze asymmetric reactions,and two years ago scientists discovered human telomere G-quadruplex DNA(G4DNA,repeat sequence GGGTTA)also has the same functions.This thesis paper is based on these studies,we were employ Oxytricha G4DNA(repeat sequence GGGGTTTT)and its expansion sequences to investigate their catalytic functions on Diels-Alder reaction and ABTS oxidation reaction in aqueous media.The main results obtained are summarized as follows:(1)Through the study,we found G4DNA metalloenzymes assembled with different repeat sequences and Cu2+ ion have different catalyzed capability for Diels-Alder reaction.In aqueous media with Na+ ion,the G4TG4-Cu2+ metalloenzyme had the maximum enantioselectivity was 46%ee;when Na+ replaced by K+,OXY28(G4T4G4T4G4T4G4)-Cu2+ and OXY22(G4T2G4T2 G4T2G4)-Cu2+ metalloenzymes had the best enantioselectivity,results were 61%ee and-34%ee,respectively.Studies have shown that different Na+,K+ concentration in aqueous solution affects the enantioselectivity of Diels-Alder reaction.Meanwhile,we used circular dichroism to collect various G4DNA sequence spectra at different Na+/K+ ion concentrations,and preliminary summarized the various-quadruplex sequence conformation according to the reference.(2)In this study,we reported that the presence of G4DNA could help improve the oxidation ability of ABTS with hemin and H2O2 in aqueous media,confirmed the potential of G4DNA on assemble oxidase.The experimental model were able to be used to detect telomerase activity,and provided some theoretical support for the G4DNA may act as functional molecules in early world.These works demonstrated not only human telomeric G4DNA has catalytic functions,but also other G4DNA has the same functions.Besides all,more research of G4DNA may provide new ways to treat cancer.