ABSTRACT

Kamzolova and Postnikova review the application of spin labels to the study of DNA. Spectra obtained from spin-labeled nucleic acids are characterized by dynamics that are faster than 1 nsec. Such fast times indicate weakly immobilized labels. Despite the problems associated with nonspecific labeling of nucleic acids, EPR may be used to obtain physical characteristics of DNA function. They cite examples from studies on the effects of conformational changes, radiation damage, binding with polymerase, and low melting regions detected by EPR spectra. The study of DNA flexibility began in 1970 when Wahl et al. examined the decay of the fluorescence polarization anisotropy (FPA) of the fluorescence dye, ethium, when intercalated in isolated DNA in solution. Hurley et al. examined the mode of binding of spin-labeled ethidium to chromatin and characterized the dynamics of the probe under a variety of conditions. SL-Ethidium binds to the regions of DNA which are not bound to the histones.