Articles you may be interested inSynthesis and characterisation of platinum (II) salphen complex and its interaction with calf thymus DNA AIP Conf.Interaction of Bis-Zn(II) salphen complex with calf thymus-DNA AIP Conf.Time-dependent correlation functions of calf-thymus DNA (Mw = l2X 10 6 dalton) and homogenized calfthymus DNA (Mw = 1.5 X 10 6 dalton) were measured by means of a 96-channel single-clipped digital photon correlation spectrometer over a range of scattering angles varying from IS' 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 timedependent 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 K 2 dependence on the linewidth (r) 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 (r I K 2) values with the translational self-diffusion coefficient which had been determined by independent light scattering and ultracentrifugal studies.Eq. (1. 1), they obtained r 2 = DK2 for the high-frequency component, indicating that 6.-l ""0 rather than a finite value as reported by Schmidt. 2 Based on the fmff C"'.)mponent of the autocorrelation function for polarited light scattering at finite angles, Schmitz and Schurr 4 then presented translational diffusion coefficients D 20 ,w varying from O. 95X 10-8 to 1. 9X 10-8 cm 2 /sec for C-T DNA measured at temperatures ranging from 56 to 86 °C.Recently, Schmitz and Pecora 5 again used a 400-point Saicor 43A autocorrelator and Showed that the timecorrelation function of C-T DNA and A DNA contained contributions from at least two relaxation processes. The authors knew that, in the limit of infinite dilution, most light-scattering theories applicable to macromolecules predicted the longest relaxation time to be due to translational diffusion. 6 Nevertheless, they concluded that, in the case of DNA, the longest time could be interpreted as possible contributions due to restricted translational motion or anisotropic diffusion. Unfortunately, in their study of C-T DNA, they were mainly interested in the behavior of rf2) and failed to report their findings on the high-frequency component (r?»). Secondly, the time-correlation functions were analyzed mainly according to Eq. (1. 2) even though in attempting to fit their measured data to Eq. (1. 2) several computations failed to converge. Again, Schmitz and Pecora 5 observed that Eq. (1. 3) holds, with r1 2 ) being the low-
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