The best flow cytometry substrate for the detection of lacZ activity
is a lipophillic FDG derivatves with 2, 4, 8 and 16 carbon acyls
known as ImaGene (Molecular Probes). However, this substrate has a
problem for the quantification of lacZ activity. We have used it to
assay b-gal activity in insect cells infected with baculovirus. A concentration
equilibrium between cell and supernatant of the hydrolysed substrate,
irrespective of enzyme activity, meant that lacZ+/lacZ- resolution
was impossible. Quantitative measurements proved problematic because the
enzyme activity showed no sign of saturation by the substrate.
Good luck
Mohamed Al-Rubeai, Ph.D.
School of Chemical Engineering
University of Birmingham