The remarkable complexity of biological systems demands a systematic approach to their analysis. The goal of this proposal is to establish an MIT Center of Excellence in Cell Decision Processes (CDP) around an interdisciplinary team of cell biologists, computer scientists and microsystems engineers tackling the systems biology of protein networks and signal transduction in mammalian cells. The basic hypothesis of the CDP Center is that understanding cell decision processes requires the development of network models that combine quantitative rigor with molecular detail. These models will be hybrids containing highly specific representations of critical reactions and abstract representations of the system as a whole. Effective models will endure and capture the accumulation of knowledge over time in a rigorous and portable format. The CDP Center will follow a research paradigm that links systematic experiments and numerical modeling in a four-step feedback loop of manipulation-measurement-mining and modeling. The biological focus of the Center will be the signaling events that control apoptosis. The measurement of protein concentrations, modification state and activity will be undertaken for signaling molecules at many points in the apoptotic network. The measurements will then be analyzed using several modeling approaches ranging from highly specified to highly abstract. To collect sufficient data for systematic modeling, the CDP Center will automate and standardize biochemical methods, develop compact array-based assays and design novel microfabricated devices with integrated microfluidics and label-free sensors. To organize and systematize the data, inforrnatic methods will be developed that support rigorous approaches to inference. Finally, physico-chemical, structure-systems and Bayesian models will be used to generate biological hypothesis for experimental verification. The research activities of the CDP Center will be complemented by graduate and undergraduate education and by an outreach program targeted at the scientific community in general and minority-serving institutions in particular