M E Galassi

Publications (5)9.58 Total impact

• Article: Distorted wave calculations for electron loss process induced by bare ion impact on biological targets.

  J M Monti, C A Tachino, J Hanssen, O A Fojón, M E Galassi, C Champion, R D Rivarola
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  ABSTRACT: Distorted wave models are employed to investigate the electron loss process induced by bare ions on biological targets. The two main reactions which contribute to this process, namely, the single electron ionization as well as the single electron capture are here studied. In order to further assess the validity of the theoretical descriptions used, the influence of particular mechanisms are studied, like dynamic screening for the case of electron ionization and energy deposition on the target by the impacting projectile for the electron capture one. Results are compared with existing experimental data.
  Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 01/2013; · 1.09 Impact Factor
• Article: Proton-induced single electron capture on DNA/RNA bases.

  C Champion, P F Weck, H Lekadir, M E Galassi, O A Fojón, P Abufager, R D Rivarola, J Hanssen
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  ABSTRACT: In this work, we report total cross sections for the single electron capture process induced on DNA/RNA bases by high-energy protons. The calculations are performed within both the continuum distorted wave and the continuum distorted wave-eikonal initial state approximations. The biological targets are described within the framework of self-consistent methods based on the complete neglect of differential overlap model whose accuracy has first been checked for simpler bio-molecules such as water vapour. Furthermore, the multi-electronic problem investigated here is reduced to a mono-electronic one using a version of the independent electron approximation. Finally, the obtained theoretical predictions are confronted with the scarcely available experimental results.
  Physics in Medicine and Biology 04/2012; 57(10):3039-49. · 2.83 Impact Factor
• Article: Ionization of uracil in collisions with highly charged carbon and oxygen ions of energy 100 keV to 78 MeV

  A. N. Agnihotri, S. Kasthurirangan, S. Nandi, A. Kumar, M. E. Galassi, R. D. Rivarola, O. Fojón, C. Champion, J. Hanssen, H. Lekadir, P. F. Weck, L. C. Tribedi
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  ABSTRACT: Fast highly charged C and O ion-induced total ionization of an RNA base molecule, uracil (C4H4N2O2, m=112 amu), has been investigated in a wide energy range of keV to MeV. A combined study of the collision products using a time-of-flight mass spectrometer and an electron spectrometer allows one to determine absolute total ionization cross sections (TCSs). Experimental measurements of TCSs are compared to theoretical predictions performed in the classical trajectory Monte Carlo and classical over-barrier (CTMC-COB) and quantum mechanical (Continuum Distorted Wave with Eikonal Initial State and first-order Born with correct boundary condition) frameworks. The overall energy dependence of the TCSs is approximately reproduced by the models, especially well in the high energy range. The CTMC-COB model provides an excellent agreement for the high-energy data. The projectile charge-state q dependence of TCSs deviates from the well-known quadratic behavior in ion-atom collisions.
  Phys. Rev. A. 03/2012; 85(3).
• Article: Quantum-mechanical predictions of DNA and RNA ionization by energetic proton beams.

  M E Galassi, C Champion, P F Weck, R D Rivarola, O Fojón, J Hanssen
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  ABSTRACT: Among the numerous constituents of eukaryotic cells, the DNA macromolecule is considered as the most important critical target for radiation-induced damages. However, up to now ion-induced collisions on DNA components remain scarcely approached and theoretical support is still lacking for describing the main ionizing processes. In this context, we here report a theoretical description of the proton-induced ionization of the DNA and RNA bases as well as the sugar-phosphate backbone. Two different quantum-mechanical models are proposed: the first one based on a continuum distorted wave-eikonal initial state treatment and the second perturbative one developed within the first Born approximation with correct boundary conditions (CB1). Besides, the molecular structure information of the biological targets studied here was determined by ab initio calculations with the Gaussian 09 software at the restricted Hartree-Fock level of theory with geometry optimization. Doubly, singly differential and total ionization cross sections also provided by the two models were compared for a large range of incident and ejection energies and a very good agreement was observed for all the configurations investigated. Finally, in comparison with the rare experiment, we have noted a large underestimation of the total ionization cross sections of uracil impacted by 80 keV protons,whereas a very good agreement was shown with the recently reported ionization cross sections for protons on adenine, at both the differential and the total scale.
  Physics in Medicine and Biology 03/2012; 57(7):2081-99. · 2.83 Impact Factor
• Article: Theoretical predictions for ionization cross sections of DNA nucleobases impacted by light ions.

  C Champion, H Lekadir, M E Galassi, O Fojón, R D Rivarola, J Hanssen
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  ABSTRACT: Induction of DNA double strand breaks after irradiation is considered of prime importance for producing radio-induced cellular death or injury. However, up to now ion-induced collisions on DNA bases remain essentially experimentally approached and a theoretical model for cross section calculation is still lacking. Under these conditions, we here propose a quantum mechanical description of the ionization process induced by light bare ions on DNA bases. Theoretical predictions in terms of differential and total cross sections for proton, α-particle and bare ion carbon beams impacting on adenine, cytosine, thymine and guanine bases are then reported in the 10 keV amu(-1)-10 MeV amu(-1) energy range. The calculations are performed within the first-order Born approximation (FBA) with biological targets described at the restricted Hartree-Fock level with geometry optimization. Comparisons to recent theoretical data for collisions between protons and cytosine point out huge discrepancies in terms of differential as well as total cross sections whereas very good agreement is shown with our previous classical predictions, especially at high impact energies (E(i) ≥ 100 keV amu(-1)). Finally, in comparison to the rare existing experimental data a systematic underestimation is observed in particular for adenine and thymine whereas a good agreement is reported for cytosine. Thus, further improvements appear as necessary, in particular by using higher order theories like the continuum-distorted-wave one in order to obtain a better understanding of the underlying physics involved in such ion-DNA reactions.
  Physics in Medicine and Biology 10/2010; 55(20):6053-67. · 2.83 Impact Factor