Chemical Effects of the Decay of ¹²⁵l in [¹⁴C , ¹²⁵l] lodobenzene in Different Solvents

Abstract

Doubly-labeled [U-14 C, 1,5 I] iodobenzene was synthesized, and its dilute solutions in hexane, benzene or methanol were stored at room or at low temperature to accumulate 1 ,S I decays. The 14 C-labeled products remaining after 1 "I had decayed were separated by gas chromatography and their yield determined radioanalytically. The fate of the highly excited [U-14 C]C,H S formed after the 155 I decay depends strongly on the matrix. In hexane aromatic rings decompose efficiently into fragments. In benzene they largely escape fragmentation, because of the ability of the surrounding ττ-electron molecules to facilitate intermolecular energy transfer. The results suggest that the charge built-up after the Auger transition and the energy deposited during neutralization, leading to super-excitation, is the main damaging event.

Mechanisms Underlying Production of Double-Strand Breaks in Plasmid DNA after Decay of125I-Hoechst

“…These strand breaks are attributed to direct, highly localized energy deposition by the cascade of electrons in the immediate vicinity (ϳ4-nm-radius sphere) of the decay site (18) and indirect effects in DNA (including adjacent molecules) mostly mediated by the cloud of hydroxyl radicals produced along the tracks of these Auger electrons after radiolysis of water molecules (19)(20)(21)(22)(23). It has also been postulated that neutralization of the high positive charge (ϳ7 ϩ ) generated transiently on the metastable 125m Te results in Coulombic repulsion between regions of the nucleotide molecular structure, leading to DNA strand breaks (3,(24)(25)(26)(27)(28).…”