**5. Conclusions**

As shown in this chapter, SMI can be used to detect molecular interactions between proteins and other biological molecules. In addition to detections of static oligomerization states, SMI allows characterization and analysis of dynamic reaction processes, including associationdissociation kinetics and enzymatic reactions.

Kinetic analyses based on SMI measurements have several advantages over analyses using conventional biochemical and ensemble-molecule imaging measurements: SMI allows quan‐ titative measurements with minimal disruption of the system integrity. Actually, SMI is ap‐ plicable to complex systems, like living cells, and avoids perturbations for synchronization. Measurements in complex systems are useful in analyses of the reaction kinetics between unknown elements, as shown in the case of RAF and the undetermined kinase(s). SMI meas‐ urements have often found novel reaction intermediates. This is because virtual synchroni‐ zation at the reaction steps and complete separation between the forward and backward reactions are allowed.

These advantages of SMI measurements make them effective in quantitative analysis of bio‐ logical reaction kinetics, providing basic information required in system-level analyses in re‐ cent molecular cell biology. In the near future, SMI measurements will be expanded to be used in pharmacology to provide novel drug screening methods and analyses of the sites of action for medical drugs, in pathology to detect currently undetermined dysfunctions of pathological mutant molecules, and in toxinology for the analyses of molecular mechanisms of toxic functions.
