Effects of Drying on Deoxyribonucleic Acids

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Abstract
Effects of drying, a frequently used storage condition, on various physicochemical characteristics of DNA has been examined in DNA solution prepared from dried-DNA and original, native DNA. Drying resulted in a decrease of viscosity, a decrease of flow birefringence, a decreased sedimentation in neutral sucrose gradient, and little change in melting temperature of DNA. They imply that the drying caused a reduction of molecular weight and molecular size by 10-20 percent with little alteration in double strand character. Gamm-irradiation of DNA solution prepared from native and dried DNA showed a remarkable difference in their responses to radiation. Thirty krads of gamma-rays caused dried-DNA to decrease its molecular weight by 70 percent and its melting temperature by 26°C, while it caused native-DNA to decrease its molecular weight by 10 percent and its temperature by 10°C. The apparent efficiency of double-strand scission of dried-DNA was 20 eV per one scission, and that of native DNA was 200 eV. The increased radiosensitivity of dried DNA might be resulted from formation of ‘hidden damages’ through drying. These results implied that the commonly used storage condition, drying, is not suitable for radiation and other studies.

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