INFLUENCE OF N 2 O AND ETHANOL ON THE CHEMICAL STAGE OF RADIOBIOLOGICAL MECHANISM

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1 INFLUENCE OF N 2 O AND ETHANOL ON THE CHEMICAL STAGE OF RADIOBIOLOGICAL MECHANISM J. Barilla *1, M. V. Lokajíček 2, H. Pisaková 2, P. Simr 1 1 J. E. Purkinje University in Usti nad Labem, Faculty of Science 2 Institute of Physics, Academy of Sciences of the Czech Republic

2 THREE STAGES OF RADIOBIOLOGICAL MECHANISM Physical stage energy transfer from particles to a water solution formation of radical clusters Chemical stage diffusion of radicals and their chemical reactions primary damages of DNA molecules Biological stage repairing of arising damages inactivation mechanisms in a cell 2

3 MECHANISM OF RADIOBIOLOGICAL EFFECT Direct effect Indirect effect Fot low-let radiation can be direct effect neglected! The decisive factor for cell damage is a double strand break of DNA molecule! 3

4 FORMATION OF RADICALS AND RECOMBINATION REACTIONS Ionization Excitation H 2 O H 2 O + + e H 2 O + H + + OH H 2 O H 2 O H + OH e + H 2 O n e aq + H 2 O OH +H e aq Formation of oxygen radicals e + O 2 O + O O H 2 O H + HO 2 O + H 2 O H + HO 2 Reaction Rate constants (dm 3.mole -1.s -1 ) 1. H + H H e aq + H H 2 + OH e aq + e aq H 2 + 2OH e aq + OH OH + H 2 O H + OH H 2 O OH + OH H 2 O H 3 O + + e aq H + H 2 O H 3 O + + OH H 2 O H + H 2 O 2 H 2 O + OH e aq + H 2 O 2 OH + OH OH + H 2 O 2 H 2 O + HO OH + H 2 H 2 O + H HO 2 + H H 2 O e aq + O 2 O 2 + H 2 O HO 2 + OH H 2 O + O HO 2 + HO 2 H 2 O 2 + O H + O 2 HO O 2 + H 3 O + HO H 2 O H 3 O + + OH HO 2 H 3 O + + O

5 INFLUENCE OF N 2 O AND ETHANOL ON THE CHEMICAL STAGE If N 2 O is present in the solution its reaction with hydrated electrons e aq to form OH radicals may be important: e aq + N 2 O N 2 + OH + OH. The presence of ethanol in the solution results in its reactions with H radicals and OH radicals C 2 H 5 OH + H C 3 CHOH + H 2, C 2 H 5 OH + OH C 3 CHOH + H 2 O, which causes their decrease and thereby protect DNA molecule against ionizing radiation. 5

6 GENERAL MODEL OF DIFFUSION AND RECOMBINATION Time change of species number dn i t dt = j k ij N i t N j t V j t + V i t j,k i k jk i N j t N k t V j t V k t dv i (t) dt = 128 D i 3 t π Formation of SSB p H = t0 t m α H N H t dt, p O = t0 t m α O N O t dt, p OH = t0 t m α OH N OH t dt p e = t0 t m α e N e t dt p S = p H +p OH +p O +p e +p 1 Formation of DSB p D = 1 2 p S 2 6

7 7

8 concentration [mmol/dm 3 ] concentration [mmol/dm 3 ] concentration [mmol/dm 3 ] CONCENTRATIONS DEPENDING ON TIME 3 2,5 2 1,5 1 0,5 0 Oxygen H OH e HO time [ns] Oxygen concentration Mmol.dm 3 N 2 O concentration Mmol.dm 3 Ethanol concentration Mmol.dm 3 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 N 2 O time [ns] H OH e HO2 3 2,5 2 1,5 1 0,5 0 Ethanol H OH e HO time [ns]

9 CONCLUSION a) The proposed simulation model makes it possible to take into account all chemical reactions running during cluster diffusion. b) The model will enable us to study the influence of LET value of ionizing radiation on DNA damage to a greater detail and to better understand the influence of chemical stage. c) It will be possible to study the influence of radioprotective and radiosensitive substances on DNA damage, which may be made use of in radiotherapy or in protection against ionizing radiation. 9

10 REFERENCES 1. Barilla, J., Lokajíček, M.: The role of Oxygen in DNA Damage by Ionizing Particles, Journal of Theoretical Biology 207, (2000). 2. Barilla, J., Lokajíček, M., Pisakova, H., Simr, P.: Simulation of the chemical phase in water radiolysis with help of Petri nets. Curr Opin Biotechnol. 22, S58-S59 (2011). 3. Barilla J., Lokajíček M., Pisakova H., Simr P.: Analytical model of chemical phase and formation of DSB in chromosomes by ionizing radiation. Australasian Physical & Engineering Sciences in Medicine. 36, ISSN DOI: /s (2013). 4. Barilla, J., Lokajíček M., Pisakova H., Simr, P.: Modeling of the chemical phase of radiobiological mechanism. Curr Opin Biotechnol. 24, S62-S63 (2013). 5. Barilla, J., Lokajíček, M., Pisakova, H., Simr, P.: Simulation of the chemical stage in water radiolysis with the help of Continuous Petri nets. Radiation Physics and Chemistry. 97, DOI: /j.radphyschem (2014). 6. Barilla, J., Lokajíček, M., Pisakova, H., Simr, P.: Modeling of the chemical stage in water radiolysis using Petri nets. Journal of Physics: Conference Series 490 (2014) , DOI: / /490/1/ (2014). 7. Barilla, J., Lokajíček, M., Pisakova, H., Simr, P.: Applying Petri nets to modeling the chemical stage of radiobiological mechanism. Physics and Chemistry in Solids. 78, , DOI: /j.jpcs (2015). 8. Barilla, J., Lokajíček, M., Pisakova, H., Simr, P.: Influence of oxygen on the chemical stage of radiobiological mechanism. Radiation Physics and Chemistry. 124, , DOI: /j.radphyschem (2016). 10

11 THANK YOU FOR YOUR ATTENTION

MODELING OF THE CHEMICAL STAGE OF RADIOBIOLOGICAL MECHANISM USING PETRI NETS

MODELING OF THE CHEMICAL STAGE OF RADIOBIOLOGICAL MECHANISM USING PETRI NETS J. Barilla 1, M. V. Lokajíček 2, H. Pisaková 2, P. Simr 1 1 J. E. Purkinje University in Usti nad Labem, Faculty of Science