Project Significance:
Photolysis of aryl azides in aqueous solutions containing guanosine, 2’-deoxyguanosine or some C8-substituted guanine derivatives enabled the use of nanosecond-LFP and nanosecond-time-resolved resonance Raman (ns-TR3) experiments to directly observe and characterize C8-intermediates that are formed prior to loss of the C8 proton (or substituent) to give the C8 adduct final product. These kinetic and spectroscopic studies using monomeric guanine have provided valuable characterization and insight into the reaction mechanism of guanine derivatives with arylnitrenium ions and have confirmed the existence of the C8-intermediate and suggest the arylnitrenium-N tends to attach very fast to the guanine-C8 position. However, there are still important unanswered questions for how arylnitrenium ions attack guanine residues of DNA oligomers. For example, are there any dif-ferences between the monomeric and polymeric (or oligomeric) guanines in their reaction with ar-ylnitrenium ions? Does the primary structure of DNA influence the reaction of DNA with arylnitreni-um ions? Here we have employed nanosecond-transient absorption (ns-TA) and ns-TR3 spectroscopies and DFT to directly observe the reaction of the 2-fluorenylnitrenium ion with selected DNA oligomers and de-tected an intermediate possessing a similar C8-structure with the intermediates produced from the re-action of monomeric guanosine derivatives with arylnitrenium ions. Our results suggest that the oli-gomeric structure can lead to a faster reaction rate of arylnitrenium ions with guanine residues in DNA oligomers and the reaction of arylnitrenium ions proceeds in a manner similar to reactions with mon-omeric guanosine derivatives.
Results Achieved:
Our results suggest that the oligomeric structure can lead to a faster reaction rate of arylnitrenium ions with guanine residues in DNA oligomers and the reaction of arylnitrenium ions take place in a manner similar to reactions with monomeric guanosine derivatives.
