UV photoelectron and ab initio quantum mechanical characterization of nucleotides: the valence electronic structures of 2'-deoxycytidine 5'-phosphate

He I UV photoelectron spectroscopy and ab initio molecular orbital calculations with the 4-31 G basis set have been employed to characterize the valence electronic structures of neutral and anionic 2'-deoxycytidine-5'-phosphate (5'-dCMP). Theoretical ionization potentials (IP's) of neutral molecules and of anions have been obtained by applying Koopmans' theorem to ab initio SCF results. The present description of orbital structure in anionic 5'-dCMP suggest that in electrophilic attack of nucleotides, product distributions of electrostatically controlled reactions will be different from product distributions of orbitally controlled reactions. A comparison of DNA and RNA alkylation patterns in methylation and ethylation reactions supports this conclusion.