DNA Compaction and Charge Neutralization Regulated by Divalent Ions in very Low pH Solution

• Published in: Polymers Vol. 11; no. 2; p. 337
• Main Authors: Gao, Tianyong, Zhang, Wei, Wang, Yanwei, Yang, Guangcan
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 15.02.2019; MDPI
• Subjects: Cell cycle; charge neutralization; Divalent cations; DNA compaction; magnesium ions; Microscopy; pH regulation; Phase transitions; United States > US; charge neutralization; magnesium ions; pH regulation; DNA compaction
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym11020337

DNA conformation is strongly dependent on the valence of counterions in solution, and a valence of at least three is needed for DNA compaction. Recently, we directly demonstrated DNA compaction and its regulation, mediated by divalent cations, by lowering the pH of a solution. In the present study, we found that the critical electrophoretic mobility of DNA is promoted to around -1.0 × 10 cm² V s to incur DNA compaction or condensation in a tri- and tetravalent counterions solution, corresponding to an about 89% neutralized charge fraction of DNA. This is also valid for DNA compaction by divalent counterions in a low pH solution. It is notable that the critical charge neutralization of DNA for compaction is only about 1% higher than the saturated charge fraction of DNA in a mild divalent ion solution. We also found that DNA compaction by divalent cations at low pH is weakened and even decondensed with an increasing concentration of counterions.