I have been using the Total Exosome Isolation (from Cell Culture Media) Reagent to isolate exosomes from my cell line. The cells do not secrete a large amount of exosomes but I get a fairly good yield using this reagent. However, I recently tried to assess the purity of my preparation by checking it for Calnexin using Western Blot and it seems to be present. I thought that Calnexin should not be present in exosome preparations. Has anyone else had similar results when using this reagent? What does it signify - contamination with soluble protein/cell debris/other extracellular vesicles? I have been following the protocol that comes with the Total Exosome Isolation Reagent exactly and according to the Nanosight most of the particles in my preparation are around 125nm (mode) with none greater than 450 nm. Is there anything else I can/should do?