13C spectrum of oligodeoxynucleotide 18 annealed with its complement to yield the duplex 5'-d(GCTAGCXAGTCC)-3'•5'-d(GGACTCGCTAGC)-3', X=γ-13C-OH PdG, adduct 2. The bottom spectrum was collected in the first day after annealing the duplex. The top spectrum was collected after 6 days at 37 °C. Assignments of resonances: a, aldehyde 3; b, hydrated-aldehyde 3a; c, carbinolamines 4.