Dyamics of calf-thymus DNA by single-clipped photon correlation

Time-dependent correlation functions of calf-thymus DNA (Mw=12×106 dalton) and homogenized calf-thymus DNA (Mw=1.5×106 dalton) were measured by means of a 96-channel single-clipped digital photon correlation spectrometer over a range of scattering angles varying from 15° to 120°. Several models as well as the method of cumulants were used to analyze our experimental data which were found to contain at least two decay times. While we agree with earlier findings on the complexity of the time-dependent correlation functions for DNA, our results have led us to different conclusions. For example, we could not find the ’’longest relaxation time.’’ Instead, we observed a simple K2 dependence on the linewidth (Γ) of the low-frequency component of time-dependent correlation functions at small scattering angles, where K is the magnitude of the momentum transfer vector. Furthermore, we were able to identify those low-frequency component (Γ/K2) values with the translational self-diffusion coefficient which had been determined by independent light scattering and ultracentrifugal studies.