I recommand an excellent book: Perrin,D.D. & Dempsey B. "Buffers for pH
and Metal Ion Control", Chapman and Hall, Ed. 1974.
I suggest Good's buffers are probably the best ones to use as they are
zwitterionic and easy to prepare (e.g. as stock solutions) thanks to the
Henderson-Hasselbalk' equation.
Apart from binding metals, phosphate has also a problem with
concentration as its activity coefficient changes dramatically with it
(as all multi-acids).
I have attached a table from an old booklet from Calbiochem.
HTH
Nadir Mrabet
Pr. Nadir T. Mrabet
Structural & Molecular Biochemistry
N-gere - INSERM U-954
University of Lorraine, Nancy
School of Sciences and Technologies
& School of Medicine
9, Avenue de la Foret de Haye, BP 184
54505 Vandoeuvre-les-Nancy Cedex
France
Phone: +33 (0)3.83.68.32.73
Fax: +33 (0)3.83.68.32.79
E-mail: Nadir.Mrabet <at> univ-lorraine.fr
Cell.: +33 (0)6.11.35.69.09
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On 20/03/2013 07:59, 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
>
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