code: public static final boolean isCharged(char aa) {
  		if (negChargedAAs.contains(String.valueOf(aa))) {
  			return true;
  		}
  		else if (posChargedAAs.contains(String.valueOf(aa))) {
  			return true;
  		}
  		return false;
  	}
docs: At pH=7, two are negative charged: aspartic acid (Asp, D) and glutamic acid (Glu, E) (acidic side chains),
  and three are positive charged: lysine (Lys, K), arginine (Arg, R) and histidine (His, H) (basic side chains).
  
  @param aa The one-letter amino acid code
  @return true if amino acid is charged