“…The measurement of an absorption or electronic circular dichroism (ECD) spectrum is one of the first and most basic steps to identify and characterize the static and dynamical behavior of a DNA sequence. − Indeed, the formation of a DNA duplex is mirrored by typical changes in the UV absorption spectrum relative to the isolated nucleobases, typically manifested as a relatively large hypochromic effect. ,, At the same time, the different possible duplex conformations, that is, B-DNA, A-DNA, and Z-DNA, are characterized by well-defined ECD signatures. , Unfortunately, the UV light absorption by DNA has also potentially harmful consequences, since it can trigger a cascade of photophysical and photochemical processes − that can lead to apoptosis or to the damage of the genetic code and, therefore, to carcinogenesis. , The study of the interaction between DNA and UV light is thus important from several perspectives, from the (bio)analytical to the (bio)medical one, explaining the huge number of experimental and theoretical studies devoted to characterize the photophysics of oligo- and polynucleotides. − Independently of the particular aspect of the UV/DNA interaction one is interested in, a proper inclusion of conformational effects is surely important. Despite the overall stability, at room temperature, DNA (and RNA) are fluctuating multichromophore assemblies (MCAs), , which can exhibit significant deviations from the “average” structure, with consequent different interactions with UV light.…”