Excited State Pathways Leading to Formation of Adenine Dimers

The reaction intermediate in the path leading to UV-induced formation of adenine dimers A=A and AA* is identified for the first time quantum mechanically, using PCM/TD-DFT calculations on (dA)(2) (dA: 2'deoxyadenosine). In parallel, its fingerprint is detected in the absorption spectra recorded on the millisecond time-scale for the single strand (dA)(20) (dA: 2/deoxyadenosine).