Hi there,

Usually increasing the protein concentration increases the oligomerization. It also depends on the oligomerization process. It might be induced by the binding of a ligand for instance. In that case you will have to add ligand to your protein sample. In any case if you need homogenous sample you will have to run SEC in order to separate the different forms.

If your protein has appreciable (theoretical) charge increase the buffer salt concentration (this can been seen from the sequence).You may also try density gradient centrifugation,or in case a ligand induces the aggregation follow the suggestion of@dominique.

If you do some negative staining EM you can try Grafix protocol to crosslink your oligomerization state and stabilized your complex.