Hi, I am doing an enzyme kinetic study and I am having problem with the fluorescence reader I am using. It is a Varioskan from thermo. When I start the reaction with the substrate (using a dispenser), the fluorescence signal changes to 0 after a few seconds. It doesn't happen in all wells, but usually occurs when the signal foes above 100 (the machine should read up to 1000). I have asked the company, but so far they couldn't help me. Does anyone know what the problem is? I have spent so much time with that problem and I am really getting frustrated!! Thanks for your help!