Acidity and proton affinity measurement of cytosine by multiple methods in the gas phase

The measurement of the intrinsic acidity of nucleic bases is essential for understanding the fundamental properties in biological systems. The Hydrogen bonding is critical to DNA stability and reactivity of oligonucleotides. The strength of hydrogen bonding can be gauged by the intrinsic acidity of the donor NH groups and the intrinsic basicity of acceptor atoms. Acidity is also indicative of the leaving group ability of a nucleobase in deglycosylation processes. In this dissertation, we examine the gas phase acidity and proton affinity of cytosine using Fourior transform mass spectrometry (FTMS), liquid chromatography mass spectrometry (LCMS) and ab initio calculations at B3LYP/6-31+G*. The experimental gas phase acidities and proton affinities were established using bracketing method, equilibrium method and Cooks kinetic method. Finally, we discuss the tautomer problem and deuterated experiments and the possible mechanism of the base excision repair by TDG enzyme.M.S.Includes bibliographical references (p. 27-28)