(57) [summary] The present invention provides a useful optical probe as an optical probe or sensor of post-translational type modifications, such as phosphorylation. The present invention comprises a polypeptide moiety comprising a recognition motif and a protease site for post-translational type modification, attached to the probe portion. Modification of polypeptides by post-translational type modification, protease alters the rate at which cleaves the polypeptide, said alteration is sensed by a measurable change in at least one optical property due to cleavage of the optical probe. The present invention also provides a vector comprising the recombinant nucleic acid encoding a recombinant nucleic acid molecule encoding a optical probe, and the optical probe also includes a host cell or cell library. The optical probe can be used in a method for the sample containing cells or samples from tissue determining whether containing post-translational type modification activity. Using such methods, the test compound can be measured whether or not to change the activity of the modified activity, thereby, can be used for the particular pharmaceutical composition. Identification of such pharmaceutical compositions may be automated using a system comprising an optical probe.