Hello,
I need to take the sodium nucleotide salts I have available in my lab and modify them to instead contain some more exotic counterions. Can I do this by binding my nucleotides to a strong anion exchange resin, washing, and eluting with a salt of my preferred counter ion?
Thanks very much!
Nikhil
Depending on the concentration of sodium in your target solution/experimental system, and the other ions, it might be sufficient to add the respective ions as soluble salt and maybe allow some time for equilibrating.
Otherwise, you could use ion exchange or (repeated) precipitation with e.g. isopropanol or ethanol from a solution with excess off the desired ion.
Yes You Can Modify Your CounterIon of Peptide Salt. by simply Using the Metal salt(modified). but one thing kept in your mind Metal having lower the Standard Reduction Potential(SRP) to the Sodium. As we know the Standard Reduction Potential of sodium is -2.71 (V) . And Standard Reduction Potential of Lithium is -3.05 (V). so you can change your counterion.
You can do either of two things:
1. First, convert a Dowex cation exchanging resin, H+ form, to the desired ionic form by washing with 0.5-1M solution of a salt containing the desired cation followed by the extensive washing of the resin with water. Next, pass, at a slow flow rate, an aqueous solution of your nucleotide through a column containing min. 10-fold excess of the resin prepared as above and wash the column with several volumes of water to complete the elution of the nucleotide. Freeze-drying will give you your nucleotide in the desired ionic form.
2. If your nucleotide is retained on a C18 reverse phase column, you can dissolve the nucleotide in a solution containing the desired cation and apply the solution to the column. Next, wash the column with 3 volumes 0.1 M aqueous solution of the salt containing the desired cation. Next, wash the column with water, min 1 column volume. Finally, elute the nucleotide with 10-15% aq acetonitrile and evaporate the eluate to dryness. It would be advantageous to monitor the UV absorbance of all eluates by an on-line detector and collect only the UV-absorbing fractions. Not all nucleotides are retained by C18 reverse phase, particularly in the step of washing with water. If you decide to use this method make sure to check all eluted fractions.
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