Single-electron-loss cross sections of DNA and RNA bases impacted by energetic multicharged ions: A classical Monte Carlo approximation

Abstract

Electron loss from the four DNA nucleobases, namely, adenine, cytosine, thymine, and guanine as well as from RNA uracil base produced by high-energy impact of multiply charged bare ions are here theoretically investigated via a simple model combining two classical approximations-the classical trajectory Monte Carlo and the classical overbarrier-previously used with success to describe the ionization of water molecules by ions. We give in the present work an estimation of the single-electron ionization and single-electron capture cross sections for different incident projectiles, namely, H + , He 2+ , and C 6+ ions with impact energies ranging from 10 keV/amu to 10 MeV/amu. The obtained results are compared to the rare theoretical predictions available in the literature and therefore highlight binding effects whose existence has been already demonstrated in the case of atomic collisions but not for ͑so͒ large molecular systems.

Fragmentation of adenine and uracyl molecules through electron captures in collisions with ions

“…Using a method combining the classical over barrier transition model and the statistical approach used in the classical trajec tory model, the cross sections of single electron cap ture, capture with ionization, double capture, single ionization, and double ionization were calculated for ion-molecular systems with adenine, He 2+ + Ade, and cytosine, He 2+ + Cyt, in the collision energy range 25-3000 keV/amu [24]. With the same technique, the cross sections of single electron loss (single electron capture plus single electron ionization) by molecules of all five NA bases in their collisions with H + , He 2+ , and C 6+ ions were calculated in the energy range from 10 keV/amu to 10 MeV/amu [25].…”

On the use of additivity rules to estimate electron production cross sections in proton-biomolecule collisions

“…The additivity rules lead to cross sections in very good agreement, for E > 50 keV, with the CDW-EIS calculations [5] for all bases, and a less satisfactory agreement with CB1 [4] and CTMC-COB calculations [3]. It must be noted that Champion et al [25] have studied the validity of the these calculations for H + + Adenine, and they estimate that the CB1 method is useful for E > 60-70 keV and the CTMC-COB for energies larger than 200-300 keV, which are the energy ranges where those calculations agree with the results of applying the additivity rules.…”

“…There is also a good agreement between the values estimated from the AR (10) and the calculations of reference [10] in the range E > 100 keV, where those calculations were performed. The cross section reported by Tabet et al [7] at E = 80 keV are almost one order of magnitude higher than those estimated using the ARs and it also overestimates the calculated values of references [3] and [10].…”

“…Experimental values: , [7]; •, [10]. Calculations: (-· -·), [3]; (- * - * ),CB1 results reported in reference [10].…”

“…Cross sections for EP in proton collisions with nitrogenous bases have been calculated by Lekadir et al [3], using a classical over barrier treatment (CTMC-COB); Champion et al [4] used the first Born approximation; Galassi et al [5] employed the first Born approximation with corrected boundary conditions (CB1) and the continuum distorted wave-eikonal initial state treatment (CDW-EIS) approximations. In general, the calculations are limited to high collision energies where the perturbative methods are appropriate and they are not able to reproduce the maximum of the total cross section.…”