This Small Business Innovation Research Phase I (SBIR) project will apply Multi Photon Detection (MPD) to quantify the minute amounts of proteins contained in and secreted from a single cell. The successes of genomics have led to the need for improved knowledge of the protein content of cells (proteomics). The elucidation of all proteins requires better methods for the study of low abundance proteins because the majority of "molecular switches" are expected to be expressed at less than 10,000 copies per cell. The<br/>goals of this project are to further improve the sensitivity of the MPD-enhanced immunoassays down to<br/>the level of a few zeptomole/sample, to study intracellular processing of the important family of cytokines (IL-1, IL-18) and to study the levels of caspases in a single cell.<br/><br/>The commercial applications of the technology to be developed in this project are in the rapidly expanding proteomics market, especially in the area of low abundance proteins proteomics. This market is currently estimated at around $ 200 million and expected to grow severalfolds over the next few years.