I have a problem with long term storage TRAIL protein.
I cloned this TRAIL protein into pET28a vector and purified it.
The final storage buffer is 20 mM Tris pH 7.5, 400 mM ammonium sulfate, 10 uM ZnSO4 (based on the formular from commercial TRAIL). However, just 2 weeks after storing at -80 deep freezer, my protein shows aggregation. It' not visible yet can be detected by DLS.
Since I will deliver this protein by nanoparticles, I don't want to add other components such as glycerol or DTT. And the aggregation occurred even faster when I stored protein in 20 mM HEPES buffer, 150 mM NaCl.
Anyone has experiences with recombinant TRAIL protein? What can I do to stabilize it?
