Cross-linking of Deoxyribonucleic Acid to Protein following Ultra-Violet Irradiation of Different Cells

Abstract

IF deoxyribonucleic acid is exposed to ultra-violet light, especially to the 2537 Å. mercury arc line, a variety of changes occur. In very dilute solution the first physicochemical change is denaturation leading to a fall in viscosity without a change in molecular weight¹. With higher doses, main-chain scission occurs and this is markedly enhanced by the presence of oxygen. There is chemical evidence for the formation of a dimer when thymine is irradiated in frozen aqueous solution² and for cross-linking between molecules when DNA is irradiated in dilute solution³ or as a thin film⁴. The work reported here has shown that the changes produced in DNA when irradiated as a nucleoprotein inside cells are qualitatively and quantitatively different from those that are produced when pure DNA is treated.