Actin staining is very useful in determining the structure and function of the cytoskeleton in living and fixed cells. The actin cytoskeleton is a very dynamic and labile structure in the living cell, but it can be fixed with paraformaldehyde prior to probing or staining for actin structures.
Phalloidin is a seven amino acid peptide toxin from the mushroom Amanita phalloides, which binds specifically and with high affinity (Kd 20 nM) to the polymerized form of actin (F-actin). Phalloidin lowers the critical concentration of actin polymerization to less than 1 µg/ml, thereby acting as a polymerization enhancer. Phalloidin has been labeled with a proprietary green fluorescent dye which allows it to be used to stain actin filaments in tissue cultured cells and tissue sections (1, see Figure 1) and cell-free preparations. Acti-stain™ 488 phalloidin-labeled actin filaments retain many functional characteristics of unlabeled actin including their ability to interact with myosin. Actin-stain™ 488 phalloidin is supplied as an orange solid.