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I have a buffer system which contains multiple salts and in addition DTT and n-Dodecyl-beta-D-maltoside.

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I understand that DTT is hydrolysing quite fast and this component must be used always fresh to keep it's reductive capacity. I am wondering however, what your experiences are with the stability of n-Dodecyl-beta-D-maltoside buffer solutions? The solid substance must be stored at -20 degrees. It is quite tedious to always weigh in all the buffer components because of the instability of some components. I had therefore the idea to maybe mix 1 l of all stable components and than take for example 50 ml and add the DTT as a solid substance (or liquid stock?) and maybe also the DDM surfactant if it is not long term stable. This would save time and resources, because the anorganic buffer salts are usually stable and the premix could also be sterilized in an autoclave. I know, that the concentration would be slightly shifted, because adding DTT and DDM (10 mM and 0,04 wt% in final solution for example to 50 ml of buffer pre mix would also slightly alter the volume of the solution, but I assume the error would be under 1%. Do you think this is feasible? What are your experiences with stability?

In terms of the stability I have also a different question: To bring one inhibitor in solution in buffer me tried to adjust the pH of the buffer a bit. When it got too basic, the solution led to white flaky precipitate. I would account this to the maltoside, which is not stable in solution in pH 9?

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  • $\begingroup$ Are you wondering if you can make buffer stock without DTT and DDM and store this until needed? If so what else is in the stock? Seems this is more important. Why discuss DDM/DTT at all? BTW searched DDM and found "Stock solutions are stable for up to 3 months at 4°C." on the Sigma-Aldrich website $\endgroup$
    – Buck Thorn ♦
    Commented Feb 11 at 11:51
  • $\begingroup$ Other components are Tris HCl, MgCl2 and ZnCl2 but these are stable and sterilizable anyway. I am thinking about DTT and DDM to save money (DDM is relatively expansive in comparison to the other ingredients). So the only thing to add freshly would be DTT. Would you use it as solid or from a stock solution to save time? $\endgroup$
    – raptorlane
    Commented Feb 11 at 12:05
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    $\begingroup$ DDM is nonionic so don't see why solubility would be very sensitive to pH. Sigma-Aldrich says: "This product is soluble in water (50 mg/ml), yielding a clear to very slightly hazy, colorless solution. Sonication may be required for complete solubilization." Cayman chemical says don't keep in solution for more than a day before use. $\endgroup$
    – Buck Thorn ♦
    Commented Feb 11 at 12:59
  • $\begingroup$ I would need to try this again with miliq, the DDM and just a bit of base. I observed this multiple times already, but not sure if this relates to the surfactant. I guess a valid approach would be to prepare the buffer premix concentrated 1.01x and than add 1/100 part in volume of DTT of 1M stock in miliq that was previously frozen from alliqots to achieve 10mM. Than add the DDM. Volume error would be limited to DDM than solely ans because of the concentration of 0.04wt% relatively small. Agree? $\endgroup$
    – raptorlane
    Commented Feb 11 at 13:09
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    $\begingroup$ Your mixing protocol seems correct. DDM might slowly hydrolyze, but I'd be surprised if it's much outside of high T or extremes of pH. I would worry more about the DTT stability since it is air sensitive. I also wonder if the metal solubility might not be sensitive to pH and Tris (the latter should help, high pH will precipitate magnesium hydroxide). $\endgroup$
    – Buck Thorn ♦
    Commented Feb 11 at 17:56

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