A theory was developed to explain how charge selectivity is reversed in tight junctions (TJs) between epithelial cells when the sign of the TJ fixed charge changes. An original method that allows for the ion cavity effect was used to calculate the changes in ion solvation energies that occur upon ion transfer in TJs. An equation was derived to describe the Na⁺ to Cl^– permeability ratio of TJs as a function of the concentration and sign of TJ fixed charges and the correlation length of water. The theory agrees with published experimental data that Na⁺/Cl^– selectivity is reversed in Madin–Darby canine kidney (MDCK) cells when claudin-15 protein molecules with a changed sign of amino acid residues are expressed in TJs.

开发了一种理论来解释当TJ固定电荷的符号改变时，上皮细胞之间紧密连接（TJ）中的电荷选择性如何反转。使用允许离子腔效应的原始方法来计算在TJ中转移离子时发生的溶剂化能的变化。的方程推导来描述的Na ⁺以氯^-作为浓度的函数的紧密连接渗透性比和TJ的签名的固定电荷，并且水的相关长度。该理论与已发表的实验数据一致，即当TJ中表达具有氨基酸残基符号改变的claudin-15蛋白分子时，Na ⁺ / Cl ^–选择性在Madin-Darby犬肾（MDCK）细胞中被逆转。