Taking samples during sonication and:
1)Visualize under microscope to see burst cells
2)Measure Absorbance at 280 for DNA/RNA release
3)Centrifuge and measure the protein concentration by Bradford
Or no need to optimize after sonication, just centrifuge because all junk will be pelleted?
Yes you can use phase contrast microscopy, Bradford assay to have a look at the lysed cells and approximate total protein. I don't know what cells are you using for expression. We use E.Coli BL21 DE3 plyss and Rossetta from Agilent technologies. What we usually do is that we centrifuge the culture at high speed, resuspend the pellet in binding buffer and centrifuge again (to wash the pellet), freeze at -80 and then thaw the pellet on ice and resuspend in binding buffer, add protease inhibitors and DNAse. We sonicate the sample 10times (on ice not to overheat it) using a small probe with 15sec sonication at 8 amplitude and 45 sec rest. I usually look at the colour of the sample when it changes i assume that sonication is complete and then centrifuge at high speed to get the supernatant (whole protein). Filter the supernatant through a 0.2 um filter just before passing it through the column.hope it helps
In my opinion, sonication is not a complicated method for bacterial cell lysis. Incubation of the cell suspension in lysozyme prior to sonication may enhance the lysis process. After 15-30 sonics cycles, a reduction in the opacity due to cell lysis can be noticed with naked eyes, a good sign of cell lysis..
You can also put the lysate onto agar to see if any cells remained intact/survived
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