FITC vs Alexa 488

Matthias Haury mhaury at
Wed Mar 27 03:06:41 EST 2002

Ok guys,

I agree, one log is 10x, and I am aware of this, but I wanted to make
another point (which did not come along very well obviously, and I should
have been more explicit... - happens if you don't re-read your own mails :)

As Mario in the meantime explained this heavily depends on which antibody
(clone, company) you are comparing it with.. On the background the label
generates, on the cells you want to stain and ... And .. And..

The CD25 is our extreme exception, and you gain about one log if you compare
it with the CD25 FITC or PE from Pharmingen (don't ask me why). However in
general for most other antibodies (if you gain at all), they are more in the
range of 2-3 times better...

However I just wanted to incite people to try to use Alexa as in our hands
it gives at least as good and sometimes much better results as FITC...

Also thanks for all the comments..


>Well 6 times is a bit exagerated, but we recently labelled some
>anti-mouse-CD-25 with Alexa 488 and gained one log compared to the
>commercial FITC and PE products.... So I think it's worth labelling with
>Alexa instead of FITC, it's as easy, a bit more expensive, but for certain
>antigens worth the trial !
>>  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?

More information about the Cytometry mailing list