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I would use a low affinity metal ion binding buffer like MOPS, HEPES, or MES. The "Good" buffers all have fairly low metal-ion affinity. Phosphates will be problematic because of magnesium phosphate formation. Cheers, _______________________________________ Roger S. Rowlett Gordon & Dorothy Kline Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: [log in to unmask] On 3/20/2013 2:59 AM, Harsh Bansia wrote: > > Sorry for a simple and non-CCP4 question. > > I have determined the structures of three different mutants of a > thermostable protein by X-ray crystallography method. I feel that Mg2+ > has a role in protein stability. > > So I want to perform a thermal denaturation study by CD spectroscopy > both in presence and absence of Mg2+ ion. > > In this regards, what should be the suitable buffer for CD studies? > May I use PBS buffer ? Since phosphate sequester divalent cations like > Mg2+. Is it advisable to use PBS buffer. If so, what is maximum > concentration of Mg2+ ion that can be used say e.g. 5 mM? My protein > was in Tris buffer and lyophilized and have theoretical pI =4.56 and > maximum activity at pH 8.4. > > > Thanking you in advances, > > harsh >