Fig. 1.

The schematic diagram of the combined fluorescence microscopy and mass spectrometry experiment. After the cells are grown and quickly collected by centrifugation, a small portion of cells (∼10–100 μl) is sampled for fluorescence microscopy experiment. At this point, the experiment is performed by at least two investigators. One investigator obtains the images of sampled cells to establish subcellular localization of the studied protein, while the other one quickly collects the rest of the cells (∼1–4 g of cell pellet) and freezes them in liquid nitrogen. Frozen cells are later processed essentially as described under “Experimental Procedures” to determine the composition of the purified protein complexes and possible post-translational modifications on the purified proteins.