Vacuum UV--photophysics and photochemistry of biomolecules.

The vacuum UV radiation absorbed by biomolecules may initiate luminescence, photodestruction and photoionization processes which lead to distortions or damage of the molecular structure. To explain the mechanisms of the processes in question and the role of different molecular fragments, it is necessary to analyse the absorption spectra. The accurate determination of the photoproducts is necessary when discussing the possible scission of molecular bonds. A knowledge of the quantum yields of vacuum UV-induced processes provides information on the relative effectiveness of different processes. In particular, the most efficient destruction of purine-pyrimidine bases, nucleotides and DNA is caused by irradiation of aqueous solutions rather than solid compounds. Additional information on molecular damage mechanisms may be obtained by comparison of data obtained using ionizing UV and UV laser irradiation.