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DNA gelation in concentrated solutions
Author(s) -
Fried Michael G.,
Bloomfield Victor A.
Publication year - 1984
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360231104
Subject(s) - chemistry , divalent , dna , dynamic light scattering , ionic bonding , thermal stability , base pair , base (topology) , analytical chemistry (journal) , ion , crystallography , chemical engineering , chromatography , organic chemistry , biochemistry , mathematical analysis , mathematics , nanoparticle , engineering
Sonicated calf‐thymus DNA (200 ± 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 dynamic‐to‐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 ( T gel ) varies linearly with [DNA] from 7.5 to 17 mg/mL. Both Na + and Mg 2+ 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. Mg 2+ effectively stabilizes the gel at concentrations 10‐fold below those required for Na + . The unexpectedly large effect of Mg 2+ suggests that ion‐specific interactions may play an important role in determining gel stability.