ESPSim: A JAVA Application for Calculating Electrostatic Potential Map   Similarity Scores
  ESPSim is an open source JAVA program that enables the comparisons of protein electrostatic potential maps via the computation of an electrostatic similarity measure. This program has been utilized to demonstrate a high degree of electrostatic similarity among the potential maps of lysozyme proteins, suggesting that protein electrostatic states are conserved within lysozyme proteins. ESPSim is freely available under the AGPL License from http://www.bioinformatics.org/project/?group_id=830 
Gregory Martyn, Christopher M. Frenz