Effects of gamma radiation on the pBs-KS DNA plasmid
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2001
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REUNIAO DE TRABALHO SOBRE FISICA NUCLEAR NO BRASIL, 24.
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DNA is considered to be the most important and critical target in a cell from the point of view of radiation
damage. It is responsible for conservation and transmission of all the cell genetic information. It is constantly
submitted to different kind of damages, where repair could or couldn't take place. The energy transferred by
ionizing radiation to the DNA strands can induce mutation, carcinogenic process and cell death. The DNA damage
involves nucleotide base alterations, single (SSB) and double (DSB) strand breaks and also chromatin rupture. The
DNA strand break (mainly DSB) is the most critical damage induced by ionizing radiation. Specifically. gamma
radiation is used in a large number of illness treatment including cancer diagnosis, treatment and cure. In fact, this
radiation is the base of conventional radiotherapy using ®9Co and ?%7Cs sources. Beside, this radiation is also present
in treatment which involves neutrons and others types of particles, such as protons, alphas and heavy ions ( e.g. Ne.
Ar). The 250 MeV proton beam therapy, largely used in recent years as an effective non invasive cancer treatment.
produces gamma rays as a secondary radiation which can generate radiobiological effects on healthy tissue. This
kind of radiation with low linear energy transfer (LET) interacts with the tissue producing secondary electrons.
which directly produce excited and ionized states into the DNA strands and inducing the formation of energetic free radicals in the aqueous solution containing the DNA molecule. The DNA strand damages produced by these
interactions must be well known in order to prevent the radiobiological effects on human being The investigation
of DNA radiation effects has been very intensive in the last years!'=3), and the present study is a contribution to
better understand the mechanism of single (SSB) and double (DSB) strand breaks of pBs KS (+) plasmid DNA
with 1 MeV gamma radiation. About 10 ml of DNA was irradiated at a concentration of 15 ng/ml in a cylindrical
plastic tube (eppendorf) in the ®®Co Gamma Cell at IPEN ( Instituto de Pesquisas Energeticas e Nucleares, Sao
Paulo) facility. The dose rate was 5 kGy/h, and the biological material was submitted to total doses ranging from
0 to 200 Gy. Supercoiled (FI),Circular (FII) and Linear (FIII) forms of the plasmid were separated by agarose gel
electrophoresis at 10 volts overnight with 1% agarose. The results exhibit a decreasing of the FI plasmid fraction
and an increasing number of the FII and FIII fractions with the dose, suggesting the presence of SSBs and DSBs
in the irradiated DNA plasmid. The detectable molecule fractions of each form of plasmid were analyzed by means
of a statistical treatment[%) allowing the
calculation of the average number of SSB and DSB per plasmid for each interaction dose.These two quantities
are shown in the figure. The curve is only to guide the eyes(preliminary data).
In this analysis it was assumed that the strand break distribution obeys Poisson' laws. These calculations were
compared with the corresponding experimental data. It was found that the statistical results describe satisfactory the data for gamma radiation.
Como referenciar
ARRUDA NETO, J.D.T.; ZAMBONI, C.B.; DUARTE, C.L.; SEMMLER, R.; JORGE, S.A.C.; ARAUJO, G.W.; SHTEJER, K.; GOUVEIA, A.N.; DEPPMAN, A.; HELENE, O.A.M.; VANIN, V.R.; LIKHACHEV, V.P.; MANSO GUEVARA, M.V.; MIRANDA, A.; RODRIGUEZ, O. Effects of gamma radiation on the pBs-KS DNA plasmid. In: REUNIAO DE TRABALHO SOBRE FISICA NUCLEAR NO BRASIL, 24., 1-5 set, 2001, Aguas de Lindoia, SP. Resumos... p. 61. Disponível em: http://repositorio.ipen.br/handle/123456789/20772. Acesso em: 15 Mar 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.