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

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

Xiong Gui, Xi Kun, Zhang Xi^†, Tan Zhi-Jie^‡

(color online) (a) Spherical representation of an RNA molecule. (b) Normalized population of surface charge density from statistical analysis over the 80 RNAs whose lengths N (-nt) are in the range of [22, 158], where N and represent the number of phosphates and the radius of gyration for nucleic acids. The PDB codes of the 80 RNAs are listed in Appendix A.