Collapse of DNA caused by trivalent cations: pH and ionic specificity effects

✍ Scribed by T. J. Thomas; V. A. Bloomfield

• Publisher: Wiley (John Wiley & Sons)
• Year: 1983
• Tongue: English
• Weight: 620 KB
• Volume: 22
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360220407

✦ Synopsis

Abstract

A comparison of the condensation of T4 phage DNA by spermidine and Co(NH~3~) at pH values between 5.1 and 10.2 has been made using quasielastic light scattering to determine translational diffusion coefficients and Stokes radii. Co(NH~3~) is more effective than spermidine in causing condensation at all pH, indicating that the differences observed in previous work were not due to pH effects, as might have been inferred from recent theories of intermolecular forces. The DNA particles collapsed with Co(NH~3~) are smaller than those obtained with spermidine. The hydrodynamic radius of spermide‐collapsed structures decreases slightly with increasing pH, while the size of the Co(NH~3~)collapsed structures is almost independent of pH. These results confirm that there are specific ion effects in DNA condensation by oligocations, in addition to the dominant general polyelectrolyte effects.