Selective interaction of ultrashort ultraviolet laser pulses with components of macromolecules

The first successful experiments on selective interaction with a specific type of base in DNA and RNA are reported. It is shown that when dilute aqueous solutions of bases are irradiated by high-power ultrashort ultraviolet laser pulses, two-stage excitation of high electronic levels takes place, resulting in the formation of irreversible photoproducts. The quantum yield of photoproducts depends on many parameters and may be made essentially different for bases of different types. By varying the experimental conditions, selective interaction with a specific type of base was achieved both by irradiating mixtures of bases and by irradiating more complex components of nucleic acids.