| | Re: Why lyse on a plate and scrape?
I can confirm that trypsinizing, PBS-washing cells before lysis in tubes fairly works. Plus, with some experience, you may adjust the volume of lysis buffer to get less or more concentrated samples, which you cannot by lysing cells on plate, I mean if you lyse on plate, you can dilute your samples but never concentrate.
I usually perform at least 2 PBS washing steps, to get rid of all the trypsin. I harvest my cells in 15 ml Falcon tubes, make one wash in 5-6 ml PBS, then I transfer to eppendorf tubes, and make another wash in ~1 ml PBS and sometimes a third one in 400-500 Ál.
For each step, I remove supernatants with a vacuum pump equipped with a fine gel loading-specific tip. That represents additionnal work, but it is worth.