DNA gelation in concentrated solutions

✍ Scribed by Michael G. Fried; Victor A. Bloomfield

• Publisher: Wiley (John Wiley & Sons)
• Year: 1984
• Tongue: English
• Weight: 684 KB
• Volume: 23
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360231104

✦ Synopsis

Synopsis

Sonicated calf-thymus DNA (200 i 30 base pairs) spontaneously forms viscoelastic gels over a wide range of concentration, temperature, and buffer conditions. Quasielastic light scattering (QLS) can be used to monitor this process, because the ratio of dynamicto-static scattering intensity decreases dramatically as gelation occurs. Using QLS, we have explored the effects of DNA concentration and mono-and divalent cations on the thermal stability of DNA gels. We found that the gel-sol transition temperature (Tge,) varies linearly with [DNA] from 7.5 to 17 mg/mL. Both Na+ and Mg2+ strongly stabilize the gel state. The sharpness of the transition increases with increasing ionic and DNA concentrations. Analysis of the Na+-dependent gelation indicates that the process requires the association of one Na+ per 118 base pairs. Mg2+ effectively stabilizes the gel a t concentrations 10-fold below those required for Na+. The unexpectedly large effect of Mg2+ suggests that ion-specific interactions may play an important role in determining gel stability.