We are trying to resuspend our biotinylated oligos in buffer containing 10mM Tris pH7.5, 50mM KCl, 3mM MgCl2 and 1mM EDTA, but most of it sticking the walls of the vial and not coming off even after vortexing. We also tried heating the vial containing oligos for 10 min at 60 degrees.
Also. some amount of oligo which dissolved initially in buffer, settled down in sometime after taking it out in another vial.
Sometimes static electricity from rubbing or touching the tube makes the oligo powder stick to the sides of the tube and then when you add solvent it does not touch the oligo because an air bubble/layer protects the oligo powder a bit like trying to dissolve BSA powder by stirring. It forms a lump and dissolves badly. I would leave it on a rotating mixer overnight then take a sample and measure the OD260 to determine how much is in solution. This is best done in TE but it is a bit late for that now. I am wondering since you added both Mgcl2 and EDTA if the EDTA has chelated the Mg from the Mgcl2 which is less soluble than the sodium EDTA and has precipitated on the first tube sides and also overnight in the second tube so the precipitate is MgEDTA and the oligo is still in solution. Again measuring the OD260 will tell you how much dissolved oligo you have. Also check the pH of the edta solution. EDTA is not very soluble at pH less than 8.0
We also tried to dissolve without EDTA but still not able to dissolve.
It is still worth while to check the OD260 of the added buffer (after addition) in case the oligo has dissolved and the material on the tube is precipitated edta coming out of solution as the Ph has moved closer to acidic. Try increasing the pH of the tris buffer to 9 and redissolving
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