Experimental methods can provide accurate information on binding affinities of charged molecules to membranes, but it is not straightforward to define a concentration and model-independent binding coefficient that would correctly describe the binding affinity of charged biomolecules to membranes with a single number, as demonstrated in figure . While the relative binding affinities can be judged by examining the whole experimental binding isotherm, detailed information such as the depth of binding or the potential mechanism of penetration remains unaccessible from the experimental data alone. On the other hand, simulations that reproduce the experimental data can be used to interpret such properties from the experimental data.