Ionic Interactions
- At any given pH, proteins have charged groups that may participate in binding them to each other or to other types of molecules. For example, as the figure shows, negatively-charged carboxyl groups on aspartic acid(Asp) and glutamic acid (Glu) residues may be attracted by the positively-charged free amino groups on lysine(Lys) and arginine(Arg) residues.
Ionic residue (ARG, LYS, HIS, ASP, GLU) pairs falling with 6Å (default) contribute to ionic interactions.