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Phalloidin Conjugates
Phalloidin is a bicyclic heptapeptide isolated from the poisonous death cap mushroom, Amanita phalloides. Its high binding affinity for the grooves between filamentous actin (F-actin) over monomeric G-actin is widely used to visualize and quantitate F-actin in tissue sections, cell cultures, or cell-free preparations. Compared to actin-specific antibodies, the non-specific binding of phalloidin is negligible, thus providing minimal background and high contrast during cellular imaging. Once bound to F-actin, phalloidin shifts the equilibrium of monomers and filaments toward the filaments side and inhibits ATP-hydrolysis. The interaction stabilizes actin filaments by preventing subunit dissociation, and it promotes actin polymerization by lowering the critical concentration.
Fig. 1
Phalloidin-iFluor<sup>&reg;</sup> 488
Actin filaments visualized with Phalloidin-iFluor® conjugates. Respectively, F-actin, nucleus, and lysosomes were stained with Phalloidin iFluor® 488, Nuclear Blue™ DCS1, and LysoBrite™ Red.
When conjugated to fluorescent dyes, phalloidin can be used at nanomolar concentrations to label and visualize F-actin in fixed and permeabilized cells, cell cultures, and cell-free experiments, as well as formaldehyde-fixed and permeabilized tissue sections. Phalloidin conjugates exhibit similar affinity for all types and sizes of actin filaments, binding in a stoichiometric ratio of 1:1 (phallotoxin:actin) in both muscle and nonmuscle cells. Compared to antibodies, phalloidin derivatives' are small (< 2 kDa), and phalloidin-bound filaments do not impede the functional properties of the filaments. The small size also permits denser F-actin labeling producing more detailed stains when imaged at higher resolutions. In addition, because actin is evolutionarily conserved, the binding properties of phalloidin derivatives can be utilized in staining a wide range of animal and plant cells.
Available Phalloidin Conjugates for Staining F-actin
Phalloidin iFluor® Conjugates

Exploiting the excellent fluorescence properties of our iFluor® dyes, AAT Bioquest has developed a series of phalloidin conjugates spanning the UV-Vis-NIR spectrum, which selectively bind to F-actins. Used at nanomolar concentration, these iFluor® phalloidin derivatives are convenient for many actin-related assays. Such assays include labeling, identifying, and quantitating F-actins in formaldehyde-fixed and permeabilized tissue sections, cell cultures, or cell-free experiments. Compared to traditional fluorescein isothiocyanate (FITC) and rhodamine conjugates, Phalloidin-iFluor® conjugates offer F-actin stains that are superior in brightness and photostability. Phalloidin-iFluor® conjugates are equivalent, and in most cases superior, to Alexa Fluor® conjugates in performance.
We encourage the research community to try our Phalloidin-iFluor® conjugates with their respective protocols for a more intense fluorescence in their F-actin staining. Phalloidin-iFluor® 700, iFluor®-750, and iFluor®-790 conjugates are among the few near-infrared stains available for multicolor imaging. The sufficient spectral separation from commonly used red fluorophores.

Document: 01.0047.211015r1
Last updated Thu Oct 02 2025