[Identification techniques of small molecule drug target proteins without chemical modification and its applications: a review].

Identification of the target proteins of small molecule drugs is crucial for understanding the mechanisms of drug actions and its side effects. Conventional methods require chemical modification, which might alter the activities of the drugs. Various label-free techniques have been developed to identify drug target proteins without chemical modifications. This includes drug affinity responsive target stability (DARTS), stability of proteins from rates of oxidation (SPROX), cellular thermal shift assay (CETSA), thermal proteome profiling (TPP) and many others. Here we review the principles and applications of these label-free techniques, their advantages and limitations, as well as the most recent advances.