Complex studies have been carried out of the interactions of electrons and photons with the constituent components of nucleic acids: cytosine, thymine, uracil, guanine, D-ribose, bromouracil and fluorouracil molecules, which are used for cancer treatment.
The investigated gas state luminescence spectra of cytosine molecules initiated by electrons with energies of 40 and 60 eV was studied. In the region of 270-500 nm, molecular bands and lines with peaks at wavelengths of: 280-290, 309-316, 336, 360, 386, 415, 425-435 and 487 nm were detected. It is shown that they are the result of radiation characteristic of such molecules as OH, NCN, HNCN, CN, CNC and CH, Нβ of the Balmer series. The shapes of the obtained spectra indicate intensive fragmentation of cytosine molecules under the action of electrons.
In the conditions of longitudinal pulse-periodic discharge in mixtures of inert gases helium, argon and vapors of cytosine and thymine, luminescence spectra in the spectral range of 200-1000 nm were investigated. It was established that the luminescence spectra contain molecular bands and lines with peaks at 280-290, 310-317, 336, 360, 386, 415, 425-435, 487 (for cytosine), 280-290, 307, 310 - 317, 337, 360, 408, 432, 487 and 525 nm (for thymine). It is shown that the nature of the appearance of these bands indicates intensive fragmentation of cytosine and thymine molecules due to the processes of dissociative excitation, dissociative excitation with ionization, and excitation of electronic levels of the original molecule.
The photoluminescence spectra of water, dimexide, and sodium bicarbonate solutions of guanine under the influence of ultraviolet irradiation were investigated. Photoluminescence spectra of guanine in a neutral solution were obtained for the first time. The luminescence maximum for a water solution of guanine with a neutral pH value is observed in the region of 360 nm. For a weakly acidic solution, the luminescence maximum is observed in the region of 380 nm, as it shifts to the long-wavelength part of the spectrum. The opposite picture occurs for a weakly alkaline solution. It was established that the given spectra of various solutions reflect only the fluorescence of guanine molecules and phosphorescence is practically absent. For the first time, the photoluminescence of a neutral solution of cytosine was investigated under the simultaneous action of radiation from a xenon lamp with an excitation wavelength of λ=280 nm and a laser with a wavelength of λ=530 nm). The luminescence curve is characterized by the presence of a broad maximum in the spectral interval ~365-380 nm and an additional maximum at a wavelength of λ ~410 nm.
For the first time, the process of two-photon excitation of cytosine photoluminescence in the polycrystalline state by Nd+:YAG laser radiation (λ=530 nm) was investigated. It was established that the luminescence spectrum has a complex character and reflects the superposition of two spectra – the fluorescence spectrum and the phosphorescence spectrum.
The photoluminescence of bromo- and fluorouracil in polycrystalline states under the action of a titanium-sapphire laser with a wavelength of λ=380 nm was studied. For fluorouracil, the luminescence peak occurs at λ=450 nm for the emission lines with λ=253 nm and λ=380 nm. For bromouracil molecules, due to the effect of the halogen on the substance's fluorophore, the position of the photoluminescence maxima changes dramatically. Thus, when excited by a laser with λ=253 nm, the maximum is in the region of 360 nm, and when excited by a laser with λ=380 nm – at 500 nm.
The zonal structure of cytosine was studied.
For the first time, the photoluminescence spectra of D-ribose in the polycrystalline state under the action of laser radiation with wavelengths of 253 and 380 nm investigated, which showed that the position of the band maxima does not significantly depend on the wavelengths of their excitation, and are at λ ~490 nm for a laser with a wavelength of λ=253 nm, and at λ ~500 nm for a laser with λ=380 nm.
The mass spectra of D-ribose molecules at the temperature of 320-430 K were studied, and the peaks at m/z=31, 30, 61, 91, 121 were identified. For the first time, the energies of the appearance of the D-ribose molecule in the threshold region of the energy dependence of the effective ionization cross section were calculated.
The mass spectra of the D-ribose molecule were studied for an electron energy of 70 eV. For the first time, the energies of the appearance of positively charged fragments of the D-ribose molecule were determined and its ionization potential was determined. For the first time, the temperature dependence of the formation of positively charged ions of D-ribose fragments was investigated in a wide range of temperatures.
