FITC vs Alexa 488

Howard T Petrie h-petrie at
Thu Mar 21 17:21:32 EST 2002

Well, unless you do a direct comparison (who's got that much antibody
to waste?) it's hard to make more than an empirical judgement.  I've
made some dozens of A488 conjugates, and I would have to say that by
flow, it's definitely brighter, but my estimate would be on the order
of 2-4X.  Using mercury excitation on a fluorescent microscope,
however, it's quite substantially brighter than FITC.  So overall, I
would say the claims are reasonable.  We like the Alexa series very
much.  I have no financial association with Molecular Probes (except
that I buy their products.  Lots of them.).  HTP

>On Molecular Probes' website are claims that Alexa 488 is 6-7 times brighter
>than FITC. Preliminary evidence from our conjugations of the same antibody
>with FITC or Alexa 488 indicate no advantage from using Alexa 488. Can
anyone who compared Alexa 488 and FITC share their findings?

Howard T. Petrie, Ph.D.
Head, Laboratory of Developmental Immunology
Memorial Sloan-Kettering Cancer Center
Box 341, 1275 York Avenue
New York, NY 10021
phone (212)639-2149
fax (212)794-4019

More information about the Cytometry mailing list