This chapter discusses the photoaffinity labeling which could be used as a method that allows to unleash the reagent at a particular time and place, when the chemical affinity labeling restricts it. The chapter notes that the possibility that a labile group of appropriate reactivity cannot be incorporated into the ligand molecule without excessive disturbance of the recognition process, there are two limitations to the affinity labeling approach. The first challenge; the range of chemical reactivity of groups that can be incorporated into the ligand is limited by the fact that these groups must not react so rapidly with water that they are destroyed hydrolytically before the ligand that carries them can reach the binding site. And secondly, it is becoming clear that some biological problems require a reagent whose reactivity remains masked until the experimenter chooses to activate it. Both of the two limitations of classical chemical affinity labeling discussed above can in principle be circumvented by the use of a photogenerated reagent. © 1997, Elsevier Inc. All rights reserved.
