WAVELENGTH DEPENDENCE OF SOME EFFECTS OF ULTRAVIOLET RADIATION ON IN VITRO DNA OF PHAGE ALPHA

The wavelength dependence of some of the effects of ultraviolet radiation on the physicochemical properties of DNA of phage α irradiated in vitro are discussed. An analytical ultracentrifuge and a spectrophotometer were used to study (a) the breaking of individual polynucleotide strands; (b) the local denaturation; (c) the presence of a fraction of molecules resistant to denaturation; and (d) the increase in the buoyant density of irradiated DNA. All the curves show a slight variation of the radiation efficiency in the range 2600–2800 A, and a well defined peak at λ = 2880 A. © 1968, The Biophysical Society. All rights reserved.