I try to use valinomycin to collapse the membrane voltage of E. coli but fail. I have try the environment of different K+ concentration (from 100mM to 400mM). The valinomycin concentration I use is 1 uM. Whether it is necessary to add any other chemicals? And how about nigericin (to collapse the pH difference).
Dear Li,
What do you mean by "collapsing membrane voltage"? Do you mean to have resting membrane potential of 0 mV? If that is the case then you will need to have approximately the equal amount of K+ inside and outside (extracellular) the cells. Most cells have an internal (intracellular) K+ of about 140-150 mM, therefore if you make an external solution of 140-150 mM K, you should get a resting membrane potential of around 0 mV. I hope that makes sense to you?
best wishes, Refik
Dear Refik
Thank you a lot for your reply. Yes, what I want to is try to rest membrane potential. But I have use this drug with different concentration of K+ from 100mM to 300mM, No significant effect have seen on E. coli. Do it need some specific treatment to use valinomycin on Gram- strain?
Best wishes, LY
Dear Li,
Unfortunately I have no experience with using valinomycin.
best wishes, Refik
I never tried something like that but I've seen Valinomycin being used at up to 10 micromolar to disrupt a membrane potential. I would try 10 and 20 micromolar without adding anything extra.
If your drug is dissolved in DMSO or another solvent I would run a control experiment adding the same amount of the solvent to cells (DMSO starts having biological effects at 0.2% concentration).
Hope that helps.
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