What can I do to Tris buffer to maintain the negative charge of the plasma membrane during osmosis? Some things I can play around with are pH, the addition of ions like KCl, NaCl, MgCl2, other agents like sucrose.
Thanks!
If the adherence of the cell membranes to the beads is electrostatic in nature, the main factors affecting the strength of the interaction will be pH, ionic strength, and ion valency.
Keep the pH in the right range by using a suitable buffer at a sufficient concentration. If you are trying to maintain a pH of 7.4 or below, I would recommend switching to a buffer with a lower pKa than Tris, such as HEPES or MOPS. The concentration of the buffer should not be any higher than necessary to maintain the pH, since the buffer contributes to the ionic strength of the solution.
Keep the ionic strength as low as possible by minimizing the concentration of salts, especially divalent salts, since the ionic strength is proportional to the square of the charge of the ion.
Breaking open the cells may release a lot of calcium ion from storage within organelles. It may help to include a little bit of EGTA (e.g. 100 µM) to chelate the calcium.
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