HYDRODYNAMIC STUDY OF SHORT RANGE INTERACTIONS IN SINGLE-STRANDED POLYNUCLEOTIDES

Equations are presented for the analysis of sedimentation-molecular weight and viscosity-molecular weight data on flexible polymers, which enable determination of the effective monomer length b in nonideal solvents. The treatment is applied to published data on single-stranded polynucleotides. b decreases from 14.4 ± 0.8 Å in 0.013 M Na+ to 12.9 ± 0.8 Å in 0.2 M Na+, but appears to remain constant at higher ionic strengths. These results are consistent with the damping out of repulsive Coulombic interactions between the phosphates, and may also reflect an increase in the amount of single-stranded helix, with increasing salt. © 1969.