Intrinsic DNA fluorescence

Intrinsic DNA fluorescence is the fluorescence emitted directly by DNA when it absorbs ultraviolet (UV) radiation. It contrasts to that stemming from fluorescent labels that are either simply bound to DNA or covalently attached to it, widely used in biological applications; such labels may be chemically modified, not naturally occurring, nucleobases.

The intrinsic DNA fluorescence was discovered in the 1960s by studying nucleic acids in low temperature glasses. Since the beginning of the 21st century, the much weaker emission of nucleic acids in fluid solutions is being studied at room temperature by means sophisticated spectroscopic techniques, using as UV source femtosecond laser pulses, and following the evolution of the emitted light from femtoseconds to nanoseconds. The development of specific experimental protocols has been crucial for obtaining reliable results.

Fluorescence studies combined to theoretical computations and transient absorption measurements bring information about the relaxation of the electronic excited states and, thus, contribute to understanding the very first steps of a complex series of events triggered by UV radiation, ultimately leading to DNA damage. The principles governing the behavior of the intrinsic RNA fluorescence, to which only a few studies have been dedicated, are the same as those described for DNA.

The knowledge of the fundamental processes underlying the DNA fluorescence paves the way for the development of label-free biosensors. The development of such optoelectronic devices for certain applications would have the advantage of bypassing the step of chemical synthesis or avoiding the uncertainties due to non-covalent biding of fluorescent dyes to nucleic acids.