There are two general type of protein chips/microarray.

Firstly, the analytical microarray in which antibodies, antibody mimics (molecules which are structurally similar to antigen binding domain of antibody but do not actually functions as antibody) or other proteins are immobilized and used to measure the presence and concentration of protein in a complex mixtures.

Secondly, functional protein microarray in which sets of protein or an entire proteome are prepared and arrayed for a wide range of biochemical activity.

Functional protein chips/ microarray:

They are constructed by immobilising large number of purified protein on a solid surface. Unlike the analytical array, which are mainly developed for diagnostics, functional protein chips have enormous potential in basic research as well as drug target identification. For example: Functional protein chips have been used to conduct enzymatic assays to identify downstream targets of kinases; the substrates are covalently immobilised to individual nanowells and then individual kinases (which are radiolabelled with ATP) were added. After washing and removing kinases, phosphorylations of substrates were analysed. It was found that 1/4th of yeast kinases phosphorylates at tyrosine residue however they are a members of Ser-Thr family of protein kinases.