Crosslinking and Degradation of Deoxyribonucleic Acid Gels with Varying Water Contents When Irradiated with Electrons

Journal Article · Tue Aug 01 04:00:00 EDT 1961 · Radiation Research

DOI:https://doi.org/10.2307/3571248· OSTI ID:4024099

Lett, J. T.; Alexander, P.

DNA gels containing between 0 and 400% of water were irradiated with 1- and 2-Mev electrons. The changes in Lett and P. Alexander (Royal Cancer Hospital, London). Radiation Research, 15: 159-73(Aug. 1961). DNA gels containing between 0 and 400% of water were irradiated with 1- and 2-Mev electrons. The changes in the viscosity, molecular weight, and solubility of the DNA were determined. The degradation of the molecule due to breaks of both strands in the twin helix becomes increasingly more efficient as the water content is increased. This is attributed to the free radicals formed in the water, and in the presence of oxygen indirect action is approximately 1.3 times as efficient as direct action in producing one double break. Direct action also leads to crosslinking, and the magnitude of this process depends both on the water content and on the presence of oxygen. In dry DNA crosslinking is relatively inefficient but is not greatly affected by the presence or absence of oxygen. Crosslinking occurs more readily in DNA gels swollen with water (up to 200% water content) as long as oxygen is absent. In such gels oxygen can completely prevent crosslinking. Insoluble DXA gels are produced by radiation so long as crosslinking predominatss over degradation. As the moisture content is increased, the mobility of the molecules becomes greater and interaction between molecules occurs more readily. But at the same time the efficiency of degradation also becomes greater. These two opposing factors lead to the situation that the rate of gel firmation for a dose of lO⁶ rads at first increases as the moisture content goes up, but at abcut 200% of water it falls again, and above 300% water gel is not formed. It was concluded that direct action leads to the rupture of polynucleotide chains to give a reactive end that can, under sterically favorable conditions, combine intermolecularly to give a crosslink if there is no oxygen present. Double bresks (resulting in a scission of the DNA double helix) occur at regions of high ionization density. Radicals produced in the water produce single breaks that are not reactive and cannot give rise to crosslinks. Main-chain breaks occur from single breaks when there are two such breaks fairly close together in each of the chains. (auth)

• Research Organization: Royal Cancer Hospital, London
• Sponsoring Organization: USDOE
• NSA Number: NSA-15-024705
• OSTI ID: 4024099
• Journal Information: Radiation Research, Journal Name: Radiation Research Journal Issue: 2 Vol. 15; ISSN 0033-7587
• Publisher: Radiation Research Society
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

BIOLOGY AND MEDICINE
DENSITY
ELECTRONS
FREE RADICALS
IONIZATION
MOLECULAR WEIGHT
MOLECULES
NUCLEIC ACIDS
OXYGEN
VISCOSITY
WATER
WEIGHT