Figure 4. The potential of mean force (PMF) as a function of the distance between the COMs of PSI monomers.

The PMF as a function of the intra-peptide distance between the PSI dimer monomers at pH 3.0 (blue line) and pH 7.4 (orange line) revealed that dissociation of the dimer requires increased energy as pH is lowered from pH 7.4 (95.7 kJ mol⁻¹) to pH 3.0 (108.8 kJ mol⁻¹), possibly the result of charge neutralization of carboxylate groups at acidic pH thereby minimizing charge-charge repulsion.