Phalloidin and phallacidin are collectively called phallotoxins, which are bicyclic peptides isolated from the deadly Amanita phalloides mushroom. Phallotoxins bind specifically to F-actin filaments with high affinity (1). Fluorescently labeled phallotoxins are very useful tool for investigating the distribution of F-actin. Labeled phallotoxins have similar affinity for both large and small filaments, binding in a stoichiometric ratio of about one phalloidin molecule per actin subunit in muscle and non-muscle cells from various species of plants and animals. Phallotoxins shift the F-actin monomer/polymer equilibrium toward the polymer, lowering the critical concentration for polymerization up to 30-fold (3,4). Phallotoxins also stabilize F-actin filaments, inhibiting depolymerization by cytochalasins, potassium iodide and elevated temperatures. Moreover, phallotoxin-labeled actin filaments remain functional; labeled glycerinated muscle fibers still contract, and labeled actin filaments still move on solid-phase myosin substrates (5,6). Fluorescent phallotoxins can also be used to quantify the amount of F-actin in cells (7,8). Sulforhodamine 101 (Texas-Red) phalloidin binds to F-actin with nanomolar affinity. Fluorescent phalloidin is typically used to stain fixed and permeabilized cells, but can also be loaded into live cells via cationic liposomes. Also see the next generation CF™ dye phalloidin conjugates, which have superior brightness and photostability. Each vial (300 U) contains sufficient probe for staining ~300 samples with a staining volume of 200 uL per sample.
- λEx/λ Em(MeOH) = 591/608 nm
- Red solid soluble in MeOH
- Store at -20°C and protect from light