biotin binding to avidin after fixation?

[Joachim Goedhart]

Hallo,

As a student I'm now using the ABC (biotin-EGF, avidin, biotin-peroxydase)
system to label EGF receptors on  cells. However, we have the problem that
avidin enters cells that are fixed with 3.7% PFA. To avoid this, we want to
fix the cells after adding avidin. This is probably the only way, because
fixation after adding biotin-peroxydase will inactivate the enzyme. Does
anybody know if the biotin-binding sites will be destroyed by PFA?

Thanks,
Joachim Goedhart