Product Uses Include
Phalloidin's usefulness as a laboratory tool is well established and lies in it's ability to inhibit microfilament de-polymerization. Thus, phalloidin stabilized microfilaments are used as substrates for the identification and characterization of the ever increasing number of microfilament associated proteins. In addition, rhodamine phalloidin can be used for staining the actin cytoskeleton in cells, and also as a fluorescent marker/stabilizer for microfilaments used in motility assays.
The rhodamine phalloidin is provided as a lyophilized powder. When reconstituted with 500 µl methanol, it is at 14 µM (200 x stock).
In keeping with our policy of providing only the highest quality products, we are now pleased to inform you that Cytoskeleton is offering rhodamine phalloidin at a chromatographic purity of >99%. This is the purest phalloidin commercially available for research use.
We have determined that the microfilament stabilizing property of our product is equal or superior to any other commercially available phalloidins. Microfilaments in 70 nM phalloidin are stable at room temperature for over one week.
Figure 1. A Swiss 3T3 fibroblast stained with rhodamine phalloidin (PHDR1). The phalloidin binds specifically to F-actin and does therefore stain the actin stress fibers in the cell
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Question 1: Can I use fluorescently-labeled phalloidin to stain F-actin in living cells?
Answer 1: Unfortunately, no, phalloidin cannot be used to stain F-actin in living cells. Phalloidins are used to stain F-actin in fixed cells. Fluorescent phalloidins only bind to the native quaternary structure of F-actin which provides a low background. The correct fixation condition for phalloidin binding is 3.7% (v/v) paraformaldehyde in PBS for 10 min because it retains the quaternary protein structure which is necessary for high affinity binding of phalloidin. Methanol fixation destroys the native conformation and hence is not suitable for F-actin staining with phalloidin. To monitor actin dynamics in living cells, micro-injection of rhodamine-labeled actin (Cat. # APHR or AR05) is recommended. Please see those datasheets for more information.
Question 2: Which of the fluorescently-labeled phalloidin is the most stable/brightest?
Answer 2: The brightest and most stable of the Acti-stains is Acti-stain 488 (green fluorescence; Cat. # PHDG1). Please see the table below for additional information on all of our Acti-stains.
Stability to photobleaching* (1/2 life in sec)
Background (% of total AFU at 100 nM)
* = measured in the absence of antifade.
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