The potential of mean force (PMF) and its RMSD of the association and permeation of vitamin B₁₂ through BtuB upon coupling of the GF-SA method with umbrella sampling (US).

Every 0.2 ns, the RMSD of the PMF was computed taking into account accumulative data. The colors in the legend number each GF-SA-US simulation cycle after which the shown PMFs were computed. This means that the PMFs were calculated based on the data collected from 0 to 1^st cycle, from 0 to 2^nd cycle, etc., and from 0 to 10^th cycle.

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