Detection window and reactive form
FITC, Qihe AF488 and SF488 are candidates for green detection. FITC is an isothiocyanate; Qihe AF488 includes reactive forms such as NHS and prepared conjugates. Current SF488 products use NH2 or DBCO routes, so direct NHS labeling of primary amines does not apply. NH2 needs a compatible bridging or activation route; DBCO pairs with a target azide. Check molecular weight, input and conditions by catalog number. AF488 here denotes Qihe products; original Alexa Fluor 488 parameters require separate confirmation.
Signal intensity and photobleaching
Compare specific signal and negative-sample background at matched target concentration, similar labeling density and common instrument settings. Photostability requires repeated acquisition under fixed illumination and exposure; a single endpoint does not measure bleaching rate.
Reading the available flow example
In Qihe’s Mouse CD4 (GK1.5) example at 0.4 µg/test, CD4+ gate fractions are 23.08% for SF488 and 20.59% for Qihe AF488. These are event fractions, not fluorescence intensity. The comparator is Qihe AF488; the result does not rank brightness or photostability against original Alexa Fluor 488. See the original SF example on the homepage.
Assess the intended environment
For acidic environments or time-lapse imaging, use product-specific pH-response and photobleaching data. A dye change also requires assessment of recovery, specific binding, negative background and storage stability.