Electron spin resosnance of gamma-irradiated oriented DNA prepared by wet spinning.

When moist, oriented DNA is gamma-irradiated and its electron spin resonance spectrum is recorded at 77 degrees K, an unresolved spectrum is obtained, the amplitude of which is strongly dependent on the angle between the direction of the DNA helices and the field. Annealing at 199 degrees K gives an eight-line thymine-like spectrum which also has a marked angular dependence. For dry, oriented DNA, the unresolved spectrum dominates even at room temperature, and the spectra exhibit lower degrees of anisotropy.