Answer:
Adding a reducing agent
Explanation:
Homodimeric proteins are formed by non-covalent interactions between two identical proteins (monomers).
Some of these intermolecular interactions are mediated by disulphide bonds which can be broken by a reducing agent like beta-mercaptoethanol (2-ME).
By adding the reducing agent to the gel, it is probable that the dimer is broken and the band observed will correspond to the two identical 22.5-kDa monomers.