This book presents new developments in the study of the chemical stage of a radiobiological mechanism. The biological effect of ionizing particles in diploid cells depends on their linear energy transfer (LET) value. While for low-LET particles a pair of DSBs in the same sections of both the equal DNA molecules is to be formed by different particles in a relatively short irradiation interval, the increase of these DSB pairs at higher LET values is given by singular particles. This means that the radiobiological mechanism in physical and biological stages may be understood at least in principle, while the chemical stage represents a still rather open problem. It concerns basic process running in this stage as well as the influence of radiomodifying agents being present in a corresponding water medium during irradiation (mainly for low-LET radiation), which may be important in the regions of radiotherapy as well as radioprotection. It has been commonly assumed that this stage has been mediated by radical clusters formed by a densely ionizing end of secondary electrons. It is evident that only greater radical clusters (being able to form at least two SSBs in a given DNA molecule) may be efficient biologically. These clusters may originate, however, at different distances from DNA molecules present in a cell; they may meet a certain time after (due to heat motion and cluster diffusion). Consequently, the resulting biological effect may be influenced also by chemical processes running in diffusing clusters. A new model of corresponding cluster evolution (based on the use of a continuous Petri net and describing the concurrent influence of cluster diffusion and corresponding chemical reactions) will be presented and the possibility of its use in the analysis of a biological stage will be shown. On the basis of available data, the initial cluster characteristics (the emergence of water radicals) as well as the emergence of other radicals (if corresponding agents are present) may be established. The corresponding influence on the processes running in a biological stage may be estimated as well. (Nova)
“In radiation biology mainly the double strand breaks and to much lesser extent the single strand breaks of DNA determine the cell survival. Even in the case of low linear energy transfer irradiation (electron-, or y
-irradiation) a large fraction of the energy of the ionizing radiation is deposited in small volumes, in the so-called spurs, or blobs. In these volume elements several reactive intermediates, cations, released electrons excited molecules, etc. form in each-others vicinity. The high local intermediate concentration may facilitate multiple reactions with the large molecular mass biological molecules, e.g. DNA. These multiple reactions with high probability lead to double strand breaks. The description and mathematical modelling with the help of Petri nets of these complex reaction systems is in the centre of the manuscript written by Barilla and co-workers. Understanding the chemical steps in radiation biology is essential in cancer treatment, radiation sterilization and irradiation treatments of agricultural products. I strongly recommend the publication.” - Professor L. Wojnarovits, Professor emeritus, Editor-in-chief of Radiation Physics and Chemistry (Elsevier), Budapest
“Detailed analysis of physico-chemical processes running in water after irradiation of a living cell is of primary importance for radiobiologists to improve effectiveness of radiotherapy as well as to enhance protection against ionizing radiation. This book provides a comprehensive overview of current activity in the field of modeling of the chemical stage of radiobiological mechanism of DNA damages. Irreparable and reparable damages initiated by highly reactive radiolytic products are modeled with the help of continuous Petri nets, a structured description of ordinary differential equation, used as an integrative approach for biochemical network analysis. Engaging, and recommended for everybody interested in modeling of radiation induced damages of DNA molecules.” - Professor Dorota Swiatla-Wojcik, Lodz University of Technology, Poland
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