• I see no reason to use pre-labeled actin filaments as the labelling procedure is so simple and straightforward using standard protocols (S.J. Kron, Y.Y. Toyoshima, T.Q.P. Uyeda, J.A. Spudich, Assays for actin sliding movement over myosin-coated surfaces, Methods Enzymol. 196 (1991) 399–416 ) which I presume you have used before.
• You also have better control of your labelling that way.
• Either TRITC-phalloidin (generally denoted rhodamine-phalloidin) and Alexa-phalloidin are fine (cf. Balaz and Mansson, Anal Biochem, 2005).
• Personally I have no experience of pre-labelled actin and would not be keen on using it.

Hi,

If you need to stain actin in life cells, my lab has recently published a paper in Nat. Methods where we introduce SiR-actin, a new fluorescent probe for actin that is cell permeable,  fluorogenic and has low cell toxicity.

the paper can be found in the link

And the probes are commercially available here:

http://spirochrome.com

Hope it helps!

Luc

http://www.nature.com/nmeth/journal/v11/n7/full/nmeth.2972.html

Thanks for the input, I realize the best way would be to purify actin from chicken or rabbit muscle and label it with phalloidin for the experiment, 

 thanks Luc for this very interesting paper about fluorescent imaging in live cells, I plan to label actin in-vitro and measure its motility across myosin from my samples. 

Hi Rizwan,

all commercial sources are ok provided that you recycle the actin by subjecting it to a polymerization-depolymerization cycle to get rid of aggregates and damaged actin before using G-actin in your motility assay.

Good luck with your experiments,

Metello