Figure 4.

Solution-phase chemical microarray. Existing chemical compounds in assay buffer containing dimethyl sulfoxide (DMSO) and 10% glycerol are arrayed on the surface of the microarray. The compounds are always in solution without any chemical linking to the microarray. For homogeneous reactions, the biological target and substrate are added into each reaction dot by aerosol deposition technology, and, in the case of kinases, the reactions are initiated by spraying on ATP. The reaction products are detected by a laser scanner or imager. For heterogeneous ELISA-based reactions, such as kinase assays using whole proteins as substrates, the substrate is immobilized on the microarray surface first, before compounds are microarrayed. The kinase is then sprayed on to the array and the reactions initiated by spraying on ATP. The reactions are then detected by conventional ELISA protocols.