Formation of 5′,8-cyclo-2′-deoxyadenosine in dA::T pairs as a model of double stranded DNA: A theoretical quantum mechanics study

► Free radical C5′,C8 cyclization in dA were studied in the context of dA::T. ► Results of B3LYP and MPWB1K calculation have shown that cdA(S)::T is privileged. ► Lower energy barrier (critical point) of discussed process was found for cdA(S)::T. ► Analysis of EHB have showed the following stability: cdA(S)::T > cdA(R)::T > dA::T. ► Presence of cdAs in ds-DNA can, possibly, lead to their local geometrical changes.