Although we still consider the results obtained with the Martini simulations reasonable, in particular for the peptides, the discrepancies for the titratable residues in proteins suggest that additional parameterization efforts may be required to systematically improve the force field for constant pH MD simulations based on λ-dynamics. Such improvements would be particularly worthwhile considering coarse grained simulations pave the way to perform MD simulations of complete organelles, 66 in which many processes have a strong pH dependence. The pK a values for each titratable residue were estimated from these fits, and listed in Table . The right panel shows the protein structure with the four titratable residues highlighted in stick representation. For each of the ten titratable residues, the dots show the fraction of frames in which that residue is deprotonated.