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| Product Name | Fluor 555 Phalloidin |
| Catalog No. | RESK-0543 |
| Description | Phalloidin is a cyclic heptapeptide toxin derived from the death cap mushroom Amanita phalloides. It selectively binds filamentous actin (F-actin) with high affinity (Kd = 20 nM) without binding monomeric actin (G-actin), and is routinely used to label F-actin in tissue sections, cell cultures, or cell-free systems for qualitative and quantitative analysis. Phalloidin derivatives bind large and small filaments from muscle and non-muscle cells of both animal and plant origin with similar affinity, at a stoichiometry of approximately one phalloidin molecule per actin subunit. Non-specific binding is virtually negligible, giving excellent contrast between stained and unstained regions, which makes phalloidin conjugates an ideal alternative to anti-actin antibodies. Phalloidin conjugates are very small, approximately 12-15 Å in diameter with a molecular weight below 2000 Da, so many physiological properties of the labeled actin are preserved: labeled actin still interacts with actin-binding proteins such as myosin, tropomyosin, and DNase I; phalloidin-labeled filaments can still penetrate solid-phase myosin matrices; and glycerol-extracted muscle fibers remain contractile after labeling. Phalloidin binding prevents the depolymerization of F-actin (microfilaments) and stabilizes microfilament structure, disrupting the dynamic equilibrium of polymerization and depolymerization. This lowers the critical concentration (CC) of actin polymerization to below 1 μg/mL, so phalloidin can serve as a polymerization promoter; it also inhibits the ATP hydrolysis activity of F-actin. This product is phalloidin conjugated to the Fluor 555 dye, emitting bright, photostable orange-red fluorescence with high staining specificity and contrast, providing better staining performance than anti-actin antibodies for qualitative and quantitative F-actin detection. The binding shows no species specificity and is broadly applicable. Supplied at a concentration of 1 mg/mL. |
| Intended Use | Qualitative and quantitative fluorescent labeling of F-actin (microfilaments) in fixed cells, tissue sections, cell cultures, or cell-free systems. |
| Principle / Technology | Phalloidin, a cyclic heptapeptide from Amanita phalloides, binds F-actin selectively and with high affinity (Kd = 20 nM) at roughly one phalloidin per actin subunit, stabilizing microfilaments against depolymerization and lowering the critical concentration of actin polymerization to below 1 μg/mL. Conjugation to the Fluor 555 fluorophore provides bright, photostable orange-red fluorescence while preserving many native biological properties of actin. |
| Detection Method | Fluorescence microscopy |
| Sample Type | Fixed and permeabilized cells; tissue sections; cell cultures; cell-free preparations. Cryosections are recommended over paraffin sections, because organic solvents such as xylene or acetone used during deparaffinization interfere with phalloidin binding to F-actin. |
| Performance Range / Specifications | Molecular weight: ~1300 Da Excitation/emission maxima (Ex/Em): 556/574 nm Solubility: soluble in DMSO Concentration: 1 mg/mL Binding affinity for F-actin: Kd = 20 nM |
| Specificity | Selective high-affinity binding to F-actin (Kd = 20 nM); does not bind G-actin. Approximately one phalloidin molecule binds per actin subunit. Non-specific binding is virtually negligible, and binding is independent of species. |
| Reaction Conditions / Protocol | Fix cells with 4% paraformaldehyde in PBS and permeabilize before staining; add enough working solution to fully cover the cells. The amount required varies with cell type and staining conditions and should be optimized accordingly. Optimize the working concentration and staining time empirically. |
| Components / Formulation | Fluor 555-conjugated phalloidin, 1 mg/mL |
| Storage Conditions | Store at -20°C, protected from light and kept dry. |
| Shelf Life | 1 year when stored at -20°C, protected from light and dry. |
| Package Specifications | 300 T (30 μL per vial, 1 mg/mL) |
| Product Form | Solution, 1 mg/mL |
| Concentration | 1 mg/mL (30 μL per vial for the 300 T format) |
| Molecular Weight | ~1300 Da |
| Source / Origin | Phalloidin is a cyclic heptapeptide toxin derived from the mushroom Amanita phalloides, conjugated to a synthetic orange-red fluorophore. |
| Shipping Conditions | Shipped with ice packs. |
| Expiration Date / Stability | Valid for 1 year at -20°C, protected from light and kept dry. |
| Regulatory / Compliance | For research use only. |
| Compatibility | Staining is fully compatible with other fluorescence labels used for cell analysis, including fluorescent proteins, quantum dot nanocrystals, and other fluorophore conjugates such as fluorophore-conjugated secondary antibodies. F-actin labeled with this product retains many native biological properties of actin. Do not co-stain with click chemistry reactions (e.g., EdU labeling), which abolish the phalloidin fluorescence signal. |
| Recommended Buffer System | 4% paraformaldehyde in PBS for fixation; avoid methanol-containing fixatives. |
| Application Notes / Precautions | Avoid methanol in the fixative, as methanol can disrupt F-actin during fixation. Do not combine with click chemistry staining (e.g., EdU), which eliminates the phalloidin signal. Paraffin sections treated with xylene or acetone are not recommended; use cryosections or an anti-actin antibody instead. If fluorescence bleaches quickly, lower the reagent concentration and use low-power laser illumination to locate the field of view before switching to high-power excitation. For weak or uneven staining, optimize the working concentration and staining time, fix with freshly prepared 4% paraformaldehyde, and extend permeabilization if needed. |
| Recognition Site | Filamentous actin (F-actin) |
For research use only, not for clinical use.
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