Spin effects govern DNA/RNA nucleotide polymerization

A new radical mechanism of nucleotide polymerization is found. The finding is based on the Car-Parrinello molecular dynamics computations at 310 K with an additional spin-spin coupling term for 31P and 1H atoms and a radical pair spin term included. The mechanism is initiated by a creation of a high-energy spin-separated Mg-ATP complex in a triplet state in which the Mg prefers an uncommon chelation to the O2-O3 oxygens of the ATP. The cleavage of the complex produces the AMPand Oradicals. The latter captures a proton from acidic solution (the Zundel cation) that converts it into the OH radical. The process agrees with the protoncoupled electron transfer (PCET) mechanism. Through interacting with the HO-C3’ group of the deoxyribose/ribose the OH radical captures its hydrogen atom. The process is accompanied by producing water and the AMP radical. The AMPand AMP radicals then interact yielding a dimer. The described mechanism is easily generalized for a bigger number of adjoining nucleotides and their type. The radical mechanism is highly sensitive to the AMP-OH radical pair spin symmetry and the radius of the OH diffusion. This confines the operation of the radical mechanism: it is applicable to nucleotide polymerization through the HO-C3’ group of deoxyribose/ribose (DNA/RNA polymerization) and inapplicable through the HO-C2’ group of ribose (RNA)—a result that nature has developed over evolution.