Theoretical analysis of deoxycytidine-5'-phosphate protonation.

The electron density distribution in deoxycytidine-5'-monophosphate (5'-dCMP) molecule and dianion has been studied by the method of CNDO/2. The comparison between the results of calculation for the neutral molecule and the data obtained by Pearlman and Kim shows that there is a linear correlation between the atomic charges calculated using quantum chemistry and those derived from X-ray results. However, partial charges for the deoxyribose fragment are correlated in a nonlinear manner. The influence of the protons added to the cytosine and phosphate residues on the atomic charges and bond orders of deoxy-cytidine-5'-monophosphate has been analyzed here. The conclusion has been drawn that the semiempirical quantum-chemical CNDO/2 technique is applicable to the mononucleotide studies.