Caspase activity and apoptosis are promoted using active, dimeric Smac peptide mimetics of the general formula M1-L-M2, wherein moieties M1 and M2 are monomeric Smac mimetics and L is a covalent linker. The border of the mutual exclusion zone is segmented into portals that allow both the operator and equipment to access a common work area such as for loading material. The excitation plate carries short-wave excitation light.