Final Activity Report Summary - SMALL MOLECULE CHIP (Profiling Protein Activity on a Proteomic Scale Using Small Molecules Microarrays) With the sequence of the human genome available, the challenge at present is to assign the physiological function of genes encoded in the genome. Using deoxyribonucleic acid (DNA) microarray technology, the so-called DNA chips, it is possible to measure the expression level of every gene in a cell. However, it is important to note that there is not always a direct correlation between the expression level of a gene and the function of the protein it encodes. Regulation of protein function at the post-translational level through local environment, protein-protein interaction and post-translational processing is critical for many cellular mechanisms. Our understanding of such mechanisms and our ability to decipher the function of gene products involved in these pathways is in part limited by our capacity to measure protein activity on a proteomic scale. The overall goal of the project was to develop enabling technologies based on small molecule microarrays in order to profile the activity state of enzymes in crude cell lysates. We firstly focussed our attention on two protein families, the proteases and the kinases, as they were known to be important in post translational modifications. We successfully developed a method to prepare small molecule microarrays that were designed to measure the activity of multiple proteins simultaneously and used the developed technology to measure the difference in enzymatic activity between cells having a different phenotype. We showed that this technology could also be used to discover inhibitors in a highly miniaturised format. These developments offered important new tools for basic research and had significant applications in diagnostics and personalised medicine.