Alpha-particle-induced changes in the stability and size of DNA

The effect of alpha-particle radiation on the thermal stability and size of calf thymus DNA molecules in deoxygenated aqueous solutions was investigat ed by thermal transition spectrophotometry, pulsed-field gel electrophoresi s, and standard agarose gel electrophoresis, The thermal transition of DNA from helix to coil was studied through analysis of the UV A(260) absorbance . The results obtained for or particles of mean LET of 128 keV mu m(-1) rev eal a dual dose response: a tendency for thermal stability of the DNA helix at "low" doses, followed by an increasing instability at higher doses. The same phenomenon was observed for the mean molecular weight of DNA molecule s exposed to cr particles. The results reported here for or particles in th e low-dose region of 0-16 Gy are consistent with our previous hypothesis of inter- and intra-molecular interactions of a covalent character in gamma-i rradiated DNA molecules in the dose region of 0-4 Gy. (C) 2000 by Radiation Research Society.