I am studying interaction of zinc with a peptide. Which buffer should I use ? And what is the highest concentration of zinc can used ?
Mr. Sukumaran,
This depends on the type of interactions of interest. There are a lot of interaction types between peptides and transition metal ions.
The traditional buffer used for NMR is PBS, however since zinc phosphate is insoluble, that is not an option. Maybe try sulfate-based buffer? Zinc sulfate is fully soluble and sodium sulfate can buffer to around neutral.
Keep in mind though that electrostatic interactions are affected by the ionic strength of the media. Menenses and Anthony K Mittermaier had a paper about the effect of ionic strength on peptide-peptide interactions that may be useful for what to expect.Article Electrostatic Interactions in the Binding Pathway of a Trans...
Stoll and Blanchard have a nice chapter on buffer selection that may also help.
Article Chapter 6 Buffers
You need to check, what kind of insoluble species Zn(II) can form with your buffer. Have you checked for "Goods" buffer? Alternatively, you can addjust/control the pH of your NMR solution/sample directly with NaOH. It might be the easiest solution but you need to actively control/check the pH during your peptide Zn titration experiment.
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