Phalloidin Labeling Probes

A variety of phalloidin conjugates for filamentous (F-actin) staining are available, including fluorescent Alexa Fluor and Alexa Fluor Plus phalloidins, along with phalloidins conjugated to classic fluorescent dyes such as BODIPY, fluorescein, and rhodamine. Phalloidin staining is spectrally compatible with other fluorescent stains used in cellular analyses such as GFP/RFP, Qdot nanocrystals, and other Alexa Fluor conjugates and antibodies. Biotin‐XX Phalloidin can be used to visualize actin filaments via fluorescent streptavidin tags or standard enzyme-mediated avidin/streptavidin techniques such as in electron microscopy. Unlabeled phalloidin is available for use as a control in blocking F‐actin staining or in promoting polymerization.

Phalloidin conjugates bind to both large and small actin filaments with similar affinity in a 1:1 stoichiometry between phallotoxin and actin subunits. They do not bind G-actin monomers.

Alexa Fluor and Alexa Fluor Plus phalloidin conjugates for F-actin staining

Fluorescent Alexa Fluor dye conjugates of phalloidin are popular F-actin stains, offering color choices across the full spectral range. These phalloidin conjugates provide researchers with fluorescent probes that are superior in brightness and photostability compared to other spectrally similar conjugates.

Alexa Fluor Plus Phalloidin conjugates retain the same specificity for actin but offer 3-5 times greater sensitivity and brightness compared to the corresponding Alexa Fluor Phalloidin conjugate. This increased brightness is beneficial for challenging F-actin imaging, such as the super‐resolution microscopy methods SIM and STORM, and for reliable staining of actin stress fibers.

Features of phalloidin probes

• High specificity—binds selectively to F-actin, which allows for precise labeling of actin filaments in fixed cells and cryopreserved tissues
• Strong affinity—nanomolar binding affinity for F-actin, which ensures stable and reliable actin staining
• Extensive fluorescent conjugate options—over twenty conjugated varieties of phalloidin
• Compatibility with fixed samples—typically used with fixed cells and tissues, making them suitable for actin staining in detailed structural studies, immunofluorescence staining, and IHC applications
• Multiplexing capability—the wide availability of phalloidin conjugates enables their use in combination with other fluorescent probes and antibodies for multiplex imaging. Biotinylated phalloidin can be made use of in downstream streptavidin steps.
• Quantitative analysis—can be used for quantitative analysis of F-actin distribution and density within cells, aiding in the study of cytoskeletal dynamics. The unlabeled phalloidin can be titrated as a control.
• Ease of use—staining is straightforward and quick
• Excellent stability—exhibit good photostability, which is essential for prolonged imaging sessions and time-lapse studies
• Wide applicability—used for a range of applications, including studying cell morphology, motility, and the effects of drugs on the actin cytoskeleton