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Assay systems are methods that are used to measure the presence, amount or activity of a substance e.g. a drug, cell type or cell component. A wide range of experimental methods are used to measure different components of organic samples in assay systems.
The guanine nucleotide exchange factor SOS is a critical intermediary that transduces receptor tyrosine kinase stimulation into Ras activation. Here the authors develop a single molecule assay in which SOS is captured from raw lysates using Ras-functionalized membrane microarrays and uncover an autoinhibitory mechanism of SOS regulation.