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

Tianyong Gao,Wei Zhang,Guangcan Yang,Yanwei Wang

doi:10.3390/polym11020337

Abstract

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 × 10−4 cm2 V−1 s−1 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.

Highlights

IntroductionIn self-assembling materials, DNA molecules are closely packed, suggesting that electrostatic repulsion between negatively charged DNA in the condensed state is balanced by counterion-induced attraction [3]
DNA has promising features for use in nanotechnology and is becoming one of the most extensively used molecular building blocks for engineering self-assembling materials [1,2].In self-assembling materials, DNA molecules are closely packed, suggesting that electrostatic repulsion between negatively charged DNA in the condensed state is balanced by counterion-induced attraction [3]
We found that the electrophoretic mobility of DNA is promoted to around −1.0 × 10−4 cm2 V−1 s−1 to incur DNA compaction or condensation in solution, which corresponds to the charge of DNA that is neutralized by about 89%

Summary

Introduction

In self-assembling materials, DNA molecules are closely packed, suggesting that electrostatic repulsion between negatively charged DNA in the condensed state is balanced by counterion-induced attraction [3]. The identification of the modes of compaction was possible thanks to the remarkable contribution of the Yoshikawa group, who brought the analysis of DNA compaction to the level of individual molecules [6,7] They showed three pathways that can be followed by DNA to go from the elongated coil state to the compact state. There is coexistence between the elongated coil state and the compact state This process is usually observed when attraction is induced between DNA monomers all along the chain, either by adding small multi-valent counterions or by inducing unfavorable contacts between

Methods

Discussion

Conclusion