Pestatin A and peptide adsorption on plastic - (May/31/2013 )

Hi everybody,
I'm using pepstatin A ( http://en.wikipedia.org/wiki/Pepstatin ) as an aspartyl protease inhibitor in a inhibition assay. I think I'm having problem of adsorption on the eppendorf plastic where I do the diluition. Have you ever experienced something like that?
Do you think I should use glass vials instead of the plastic one?

thank you

Claire

how are you preparing it?

we prepare it at 1 mg/ml in methanol and store in eppendorf tubes (polypropylene). we don't seem to experience loss.

At one point I worked in a lab that studied proteins that, for whatever reason, stuck to eppendorf tubes and pipette tips all the time. To prevent this, we typically added 0.1% PEG8000 to all our buffers and this worked wonders. Occasionally we would add a little ovalbumin or BSA (0.1%) to the buffer instead of PEG, which also worked great. Basically the PEG/albumins just acted as an inert grease. You can also try using siliconized eppendorf tubes/pipette tips.