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Change Tris for Phosphate buffer cause precipitation - Which buffer can replace Tris? (Oct/04/2005 )

For biotinylation I need to avoid the buffer containing amines (ie Tris, Azides);
Up to now, my protein was OK in the buffer 50 mM Tris pH 7.0, 150 mM NaCl.

I tried to dialyse it into the buffer - 0.1 mM Phosphates pH 7.2, 150 mM NaCl, but it caused the precipitation of the protein.

Which other buffer I can taste?

(PI of my protein is 8.25)


I would recomend Hepes buffer


Try to use NaHCO3 at 0.1 mol/L
Buffer to pH8.0 or 8.5.

Check also you protein pHi...


MOPS, HEPES, or BES, depending on your desired pH. They all have pKa values between 7 and 7.5. They are all non-nucleophilic. I can see why you might want to avoid Tris (which is nucleophilic), but why avoid azide? I assume that you use azide in some buffers as a preservative.