The present invention concerns multimeric proteinaceous molecules comprising at least two members that bind each other via a region of noncovalent interaction, wherein a first of the members comprises a conditionally reactive group that, when activated, cleaves a covalent bond within the first member. Cleavage of the covalent bond results in a reduction in the binding strength with which the at least two members bind to each other via the region of noncovalent interaction. The reduction in the binding strength can result in the separation of the members under mild conditions.