To what extent of ion neutralization can multivalent ion distributions around RNA-like macroions be described by Poisson-Boltzmann theory?  

作　　者：熊贵 席昆 张曦 谭志杰 

机构地区：[1]Center for Theoretical Physics and Key Laboratory of Artificial Micro & Nano-structures of Ministry of Education,School of Physics and Technology, Wuhan University

出　　处：《Chinese Physics B》2018年第1期164-174,共11页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant Nos.11374234,11575128,11774272,and 11647312)

摘　　要：Nucleic acids are negatively charged biomolecules, and metal ions in solutions are important to their folding structures and thermodynamics, especially multivalent ions. However, it has been suggested that the binding of multivalent ions to nucleic acids cannot be quantitatively described by the well-established Poisson-Boltzmann （PB） theory. In this work, we made extensive calculations of ion distributions around various RNA-like macroions in divalent and trivalent salt solutions by PB theory and Monte Carlo （MC） simulations. Our calculations show that PB theory appears to underestimate multi- valent ion distributions around RNA-like macroions while can reliably predict monovalent ion distributions. Our extensive comparisons between PB theory and MC simulations indicate that when an RNA-like macroion gets ion neutralization be- yond a ＂critical＂ value, the multivalent ion distribution around that macroion can be approximately described by PB theory. Furthermore, an empirical formula was obtained to approximately quantify the critical ion neutralization for various RNA- like macroions in multivalent salt solutions, and this empirical formula was shown to work well for various real nucleic acids including RNAs and DNAs.Nucleic acids are negatively charged biomolecules, and metal ions in solutions are important to their folding structures and thermodynamics, especially multivalent ions. However, it has been suggested that the binding of multivalent ions to nucleic acids cannot be quantitatively described by the well-established Poisson-Boltzmann （PB） theory. In this work, we made extensive calculations of ion distributions around various RNA-like macroions in divalent and trivalent salt solutions by PB theory and Monte Carlo （MC） simulations. Our calculations show that PB theory appears to underestimate multi- valent ion distributions around RNA-like macroions while can reliably predict monovalent ion distributions. Our extensive comparisons between PB theory and MC simulations indicate that when an RNA-like macroion gets ion neutralization be- yond a ＂critical＂ value, the multivalent ion distribution around that macroion can be approximately described by PB theory. Furthermore, an empirical formula was obtained to approximately quantify the critical ion neutralization for various RNA- like macroions in multivalent salt solutions, and this empirical formula was shown to work well for various real nucleic acids including RNAs and DNAs.

关 键 词：nucleic acids ion binding Poisson-Boltzmann theory Monte Carlo simulation 

分 类 号：O4[理学—物理]