Ultrasonic Scission of Deoxyribonucleic Acid in Aqueous Solution III. The Solution Properties of Sonicated Low Molecular Weight Samples as Revealed by Light Scattering and Viscosity

Abstract

The light scattering and viscosity measurements were carried out at 25°C in 0.2 M NaCl solutions for 14 fractionated low molecular weight DNA (sDNA) samples, which were prepared by the precipitational fractionation of the sonicated calf thymus DNA fragments. The relationship between the intrinsic viscosity [η] and the weight-average molecular weight Mw could be expressed with an empirical formula, [η]=9.54×10−6Mw1.35 in cm3g−1 for 1.2×105≤Mw≤3×105, but a sigmoidal change followed with an inflection region (3×105≤Mw≤6×105). The z-averaged square radius of gyration ‹S2›z was also determined from the angular dependence of scattered light intensity for each sDNA sample. The dependence of ‹S2›z and [η] on Mw was calculated theoretically at various values of the persistence length for the A- and B-DNA conformations. It was found that the effect of the polydispersity on ‹S2›z and [η] is important, if a quantitative comparison is made between the observed and calculated quantities.