Actually, i am trying to attach amino anthracene with sodium alginate by using EDC/NHS chemistry. Amino anthracene is non-polar and only dissolve in the organic solvent. I am using phosphate buffer for alginate and DMF for amino anthracene. In the start of the reaction, amino anthracene is completely dissolved in DMF. But after EDC/NHS reaction, during dialysis it again undissolved. So, I am confused now, which solvent I should use?
Hi Syeda, you don't need to make NHS intermediates for EDC coupling.
EDC activated -COOH groups by itself crosslinks to -NH3 groups at pH~5-6 very well.
Dissolve alginate in MES buffer at ~pH 5- 6. Make a stock solution of 1M EDC in MES pH5. Do not store it. Use it immediately after making.
Separately and dropwise add EDC in MES and aminoanthracene in DMF into the solution with stirring. The crosslikinking should happen before your eyes.
MES buffer can be a good choice to start with. You can have MES with different pH values say from 3.5 to 6. Try experiments with different pH values. The pH giving you best results will be the one to use. Try repeating in similar ambient conditions for better repeatability.
I'm guessing your using 1-aminoanthracene? If so the pKa should be < that of aniline (4.6). So it might be worth trying a mixture of a water miscible solvent with your buffer (or even a slightly more acidic buffer, selective so as not to react too quickly with the EDC) could be worth trying. Stengrimur is correct about not having to use NHS.
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