Radiation damage in biomolecular systems
In the Nuclear and Environmental Research Laboratory of the Institute of Physics, the radiation damage research started in 1980. Laboratory was involved in Chernobyl accident evaluation in terms of radioactive contamination and its influence on population. Numerous calculations and experiments on radiotoxicity and radiation level determination in INPP nuclear waste are performed until now. Concerning the radiation protection, measurements of radiation doses and contaminated source identification we have at our disposal the best available experimental basis in Lithuania.
The radiation induced damage in biomolecular systems is the new activity in the Nuclear Physics Department of Nuclear and Environmental Research Laboratory developed together with Vilnius University Plant Physiology and Microbiology department and within European cooperation in the field of scientific and technical research (COST Action P9).
In the Department of Plant Physiology and Microbiology of Vilnius University the biological structures such as yeast Saccharomyces cerevisiae are investigated. This unicellular microorganism is very convenient because of growth speed, fast reproduction cycle and metabolic signal pathways having many analogies in higher eukaryotes. One can affect the population of yeast by changing their environmental conditions (physical and chemical parameters) and observe the response of object - mutation or adaptation in a short period. The main controlling parameters are alterations in cell division, cell growth and evolution. The yeast mutants with a dysfunctional RAS/cAMP signal pathway are used. By this pathway the cell receives the signals from the growth environment. Mutations originating during the cell growth under extreme conditions determine differences in the activity of RAS/cAMP pathway.
The recent two years have been dedicated to investigation of yeast prions � proteins with altered conformation. Prions are the aggregated proteins which have lost their functions due to abnormal folding mutations. The analysis of the dynamics of proteins aggregation and it dependence on the RAS/cAMP pathway activity is performed. The environmental factors which have influence on prionization and/or prion elimination from the cells are being studied. At this point the apoptosis process � programmed death of the cell - is under investigation. Apoptosis is important for cancer cells treatment. It was pointed out, that prions provide adaptability for yeast cells and prevent apoptosis.
The study of the several phenomena related to the radiation effect on behavior of yeast systems is previewed by exposing it to ionizing radiation (α, b, g, X-ray and UV).
* Investigation of the different radiation kind and dose effect on cell vital regulation processes including cell sensitivity analysis at different stages of the cell cycle.
* Radiation effect on prionization, prion elimination in the yeast cells. The lethality of the prionic protein.
* The apoptosis phenomena.
The external or internal irradiation of the sample (yeast) by desired ionizing source is foreseen. It could be a strong α source such as 239Pu, b - 90Sr and g or X-ray sources depending on the desirable dose level. The first step of the research consists of irradiation of synchronized yeast cells by X-rays. Irradiation (depending on the dose) can be concentrated on different parts of the cell (nucleus or cytoplasm) and at different stages of the cell cycle. Cell is most sensitive to irradiation at the cell cycle division stage. Viability of the cell is observed control parameter.
For detailed calculation of the deposited ionizing radiation dose in the sample (cell and its surroundings) the available simulation codes are used. A simulation model of the ionizing source and the sample allows one to obtain the exact radiation dose rate received by the yeast (nucleus and cytoplasm) during the irradiation time. Calculations and the observation of the radiation-induced perturbation of normal physiological processes, along with the biological system responses, will help to understand the damage level: free radicals production, breakup of chemical bonds, new chemical bonds production or damage molecules that regulate vital cell processes.
Publications on investigations of Saccharomyces cerevisiae (Department of Plant Physiology and Microbiology of Vilnius University):
(see link for references)
http://www.fi.lt/directions/radbio.htm