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

Abstract

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-

Quasi-elastic light-scattering investigation of microemulsions

“…The light-scattering spectrometer used in this study was similar to those described in the literature (16). The light source was the 514.5-nm line of a Lexel 2-W stabilized argon ion laser.…”

On the nature of the slow modes appearing in quasi-elastic light scattering by semi-dilute polymer solutions

“…Following the first papers of Pecora [l, 2] predicting that the spectrum of scattered light by long polymers should be composed of a large number of modes, a number of experimental papers [3][4][5][6][7][8][9][10] appeared, some reporting, the existence of several modes and some reporting the absence of several modes.…”

“…Apart from a single, but important exception [22], slow modes are only reported in polynucleotides (but not in every case). The studies on polynucleotides are numerous [5][6][7][8][9][10][17][18][19]. In most cases, the polymer under study is DNA.…”

Slow modes in semi-dilute solutions of polynucleotides

“…The situation is much less favourable as far as rigid polymers like DNA are concerned [4][5][6][7][8][9][10]. Experimenters are aware of the fact that interactions between chains might be responsible for some of the surprising behaviour of the scattered light, but one actually misses a theoretical corpus that would allow a clear understanding of the experimental results.…”