Vernon, I have been successful with a biotinylation kit from Biocare Medical. It uses a different chemistry than the Vector kits. I think the mopping reagent may be what makes the difference. Their number is 800 799 9499 ask for Hari, he's the technical sales manager. Becky Orr, CLA HT (ASCP) IHC Lead Evanston Northwestern Healthcare ph: 847-570-2771