Luminescence of the nucleic acid bases uracil molecules in different phase states under the electron beam

Background. The interaction of high-energy radiation (α, β, γ- rays or heavy ions) on living cells, basically, does not lead directly to the degradation of the biopolymer molecules, including covalent bonds in the primary structure of nucleic acids. This function is performed by the secondary electrons that are produced in large quantities during the passing of the high-energy radiation stream through biostructures. The aim of this work is to identify the luminescence of uracil molecules under electron beam in the environment where these molecules are placed on the surface of the polycrystalline matrix.
Materials and methods. Research carried out using the method of electron-photon spectroscopy. Experimental samples were the planar ceramic plates with the size 10×10×2 mm. Immobilization of biomolecules performed by their precipitate from an aqueous solution on the surface of the ceramic matrix.
Results. For the first time the radiation spectrum of the surface with absorbed molecules of nitrogenous base uracil NA under the electron beam energy of 600 eV under the conditions of ultrahigh vacuum P ≤ 5·10^-9 Thor was obtained. In the energy range of 200–800 nm three broad molecular bands with maxima at λ ~ 335 nm, λ ~ 435 nm and λ ~ 495 nm were discovered.
Conclusion. It appears that the mechanisms of formation of radiation bands caused by excitation of π - electron of the uracil molecules from the ground singlet state S₀ to S_n excited singlet state and excited triplet state T_n, with their deactivation into S₁ and T₁ states. The radiation decay of S₁ state to the ground state generates fluorescence band with a maximum at λ ~ 335 nm. Molecular band with a maximum at λ ~ 435 nm is phosphorescence band and is caused by the radiation decay of T₁ states to the ground S₀ state

electron beam, surface, uracil, spectrum, spectral bands