[Spin polymerization of DNA/RNA nucleotides]

The Car-Parrinello molecular dynamics (CPMD) has been used to study the ion-radical (IR) polymerization (triplet (T) and singlet (S/TO) states) of adenine mononucleotides upon interaction with Mg2+(H2O)2-ATP(4-). It has been found that the IR polymerization occurs only upon Mg2+(H2O)2-ATP(4-) excitation into a T state (the Franck-Condon or femtosecond laser excitation); it naturally occurs in the dark with DNA polymerase or another Mg-holoenzyme upon interaction of Mg with two Asp residues. The IR path affects only the HO-C3' group of ribose, leaving the HO-C2' group inactive. The IR polymerization starts with the homolytic removal of the hydrogen atom from the HO-C3' group and its transfer onto the hydroxyl radical *OH, a product of the ATP cleavage, which yields a water molecule. A further progress of the reaction involves interaction between two ion-radicals *AMP. The reaction is sensitive to the recombination of *OH and *AMP. It is mostly suppressed by the appearance of identically directed electron spins on both radicals (the radical pair in the T-state) in the vicinity of the HO-C3' group and not suppressed in the vicinity of the HO-C2' group (the spins in the radical pair are oppositely directed, the radical pair in the To state), making the latter inert on the IR polymerization, but allowing it to be active in the ionic (hydrolytic) polymerization.