In the last six decades a large number of mathematical methods have been developed to determine the predominant function of a protein. This work uses a graphic refinement to one of these methods, the Polarity Index Method. The results show that the polarity/charge profile of a sequence, in addition to having a distinctive profile, is self-modifying to maintain an electromagnetic balance. We consider that this regularity contributes to the understanding of the understanding between the preponderant function of a sequence and its electromagnetic balance.