Inter-atomic distances at the Na+ binding sites of the F. nucleatum c-ring, in the crystals at pH 5.3 and 8.7, and in simulation.

aCrystallographic values are averages, with the corresponding standard deviations, over the 11 binding sites in each of the two c-rings found in the asymmetric unit. The structural refinement was carried out without non-crystallographic symmetry restraints on the Na+ and HOH positions.bThe simulation values are time-averages extracted from the simulation of Model A (Figure 1A), over the 11 binding sites in the c-ring. The average structure of the c-ring backbone in simulation is superimposed on the crystal structure in Figure S14; the RMS difference is 0.74 Å.

a. 晶体学数值为不对称单元内两个c环（c-ring）各自11个结合位点的平均值及其对应标准差。结构精修过程未对钠离子（Na+）与水分子（HOH）的位置施加非晶体学对称性约束。
b. 模拟数值为从模型A（图1A）的模拟结果中提取的时间平均值，对应c环上的11个结合位点。模拟所得c环主链的平均结构已与晶体结构叠合（详见图S14），二者的均方根差值为0.74埃（Å）。