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 nonmuscle 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).

Biotin-XX phalloidin stains F-actin with nanomolar affinity. The long flexible spacer group XX facilitates interaction between biotin and avidin or streptavidin which can be labeled with a fluorophore or an enzyme for visualization of F-actin. Biotin-XX phalloidin can also be used for detecting F-actin by electron microscopy. The content in each vial is sufficient for ~100 microscope slide preparation (100 U).

• White lyophilized solid soluble in methanol
• Store at -20°C and protect from light
• C₅₇H₈₅N₁₃O₁₄S₂
• Mwt: 1240