Science and Education Publishing American Journal of Modeling and Optimization 2 4 2014 10 19 Some Critical Aspects of Molecular Interactions Between Drugs and Receptors 84 102 EN María J. R. Yunta Departamento de Química Orgánica I, Facultad de Química, Universidad Complutense, Madrid, Spain AJMO2014241 10.12691/ajmo-2-4-1 2014 09 26 2014 10 15 2014 10 19 Protonation states are sometimes crucial for free energy calculations to predict binding ability of molecules to receptors, a main subject for drug design. This mini-review seeks to identify the importance of knowing the influence of pH in such studies to better achieve correct predictions for drug candidates. Protonation states, for both proteins and drugs, need to be considered in docking studies although they have been usually neglected.