By discussing some of the results obtained in the theoretical study of the excited state behavior of realistic oligonucleotides, we shall give some insights in the complexity of the dynamical processes triggered in DNA by absorption of UV light,[1] pointing out some of the open issues and of the challenges to be tackled, which are common to several others multi‐chromophore systems. We shall focus mainly on oligoAdenine,[2,3], dipyrimidine[4‐6] and dipurine[7] steps, GC and AT single and double strands [8‐12] and Guanine Quadruplex helices[13]. Our studies show that different kind of excited states, each one often responsible of a different spectral signature and in dynamic equilibrium, are involved in the deactivation pathways. From the methodological point of view, we shall discuss some recent results in the field of the computation of spectra (absorption, emission, IR, ECD) in semi‐flexible systems.[14]

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