Fluorescence photoconversion of biarsenical-labeled cells for correlated electron microscopy (EM).

Correlated light microscopy (LM)/electron microscopy (EM) analysis can be achieved by using biarsenical dyes to fluorescently label tetracysteine-tagged proteins. Once live cell imaging using LM is complete, cellular activity can be halted promptly using a glutaraldehyde-based fixative. Rapid fixation preserves cellular ultrastructure and limits diffusion of reaction products. This protocol provides details on rapid fixation of cells, followed by fluorescence photoconversion of 3,3'-diaminobenzidine tetrahydrochloride (DAB) and sample processing for EM that can be correlated with the live cell LM images.