We are trying to dissolve amino acids (for in vitro transcription and translation), each at 2M concentration and than mix them together to get 50mM mixture of amino acids. We encountered the problem after mixing them together, they started to precipitate. What would be the best solvent and pH for the stability of dissolved amino acids?
Unfortunately, I am not so sure this is even doable with your expected concentration. At high concentration, some amino acid will need acidic conditions in order to be entirely soluble, some will need basic conditions...etc...
For example, the maximum concentration you could find in commercial solution would be the 20mM cell free mixture from Sigma, and I was never able to achieve this kind of mix by myself...
If you look at commercial kit for in vitro translation, they sometimes use 1mM concentration for AA mix. Are you sure you need a concentration that high?
Unfortunately, I am not so sure this is even doable with your expected concentration. At high concentration, some amino acid will need acidic conditions in order to be entirely soluble, some will need basic conditions...etc...
For example, the maximum concentration you could find in commercial solution would be the 20mM cell free mixture from Sigma, and I was never able to achieve this kind of mix by myself...
If you look at commercial kit for in vitro translation, they sometimes use 1mM concentration for AA mix. Are you sure you need a concentration that high?
I agree with the above. Some of the 20 proteinogenic amino acids are quite soluble in water, others are not. Best solubility is at the pH when the aa is maximally charged. This is different for each amino acid. Solubility another solvents depends on the exact nature of the side chain. I could imagine that the aromatic amino acids have better solubility in some solvents than in water. Stability is not so much of an issue for amino acids. The single exception I am aware of is glutamine. Avoid light exposure for the aromatic amino acids.
I agree with the above. You are using too high concentration of amino acids. Amino acids in the form of chlorides (AA * HCl) are more soluble than regular AA. For chromatography I did concentration of 10 mM. Very hard to dissolve all AA in ethanol + HCl + temp.
Dissolving the mixture of amino acid is no problem, you can bring the pH or Higher with HCl or NaOH etc then after dissolving adjust your target pH. But the problem also with me here is after dissolving they make precipitate after sometime. Which amino acid is responsible for this? I guess one is Cysteine due to thiol bonding? Can someone answer how to prevent precipitation?
Dear Saša Rezelj,
Have you deal with the precipitation problem? as the your question is about an year before, I hope you will solve the problem, can you guide me how to avoid the precipitation?
Dear Sasa, you can try with 30% liquid ammonia, or 1.5 M NH5CO3, 3N Hcl or 5 M NaoH, those following solvents will help u to solubilize all amino acids, I m pretty sure only leucine, isolecuine, phenylalaline, aspartic acid and glutamic acid,remaining all amino acids will defintely solubile in water, but the above mentioned 5 amino acids will cause the obstracle for solubility , in that case u use the above mentioned solvents for proper solubilization of all 16 amino acids at time. in case if your getting precipitation after pH adjustment then pass the entire amino acids mixture through 10 KDa TFF cassete, then u will get clear solution
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