Investigation of protonated base pairs between hypoxanthine and DNA bases by MS and MP2 methods

Hypoxanthine (I) is the nucleobase of inosine. In this work, we employed second-order Moller-Plesset perturbation(MP2) method to investigate the protonation properties of hypoxanthine(I), adenine(A), cytosine (C), guanine (G), and thymine (T). The order of proton affinity is as follows: cytosine (N 3 and O 2 (N 3 ) side) approximate to guanine (N 7 ) > adenine (N 1 ) > hypoxanthine (N 7 ) > thymine(O 4 (N 3 side)). To compare the stability of protonated base pairs between I and DNA bases, we investigated the collision-induced dissociation (CID) behavior of the pairs using tandem mass spectrometry method. And the full geometry optimization has been performed for the studied complexes by the MP2 method. Based on the CID results and calculated structures, the stability of the protonated base pairs in DNA decreased in the following order: (I:A + H) + > (I:C + H) + > (I:G + H) + > (I + H:T) + .

Automated summary

In this study, the protonation properties of hypoxanthine (I) and DNA bases were investigated using the MP2 method. The stability of protonated base pairs in DNA was found to decrease in the order of (I:A + H) + > (I:C + H) + > (I:G + H) + > (I + H:T) + based on CID results and calculated structures.