The effect of different buffers on terminal deoxynucleotidyl transferase activity.

The polymerization of dATP, dCTP, and dGTP onto the defined length initiator, d(pA)10, has been carried out in four buffers. The relative effectiveness of the buffers for the polymerization of each deoxynucleoside triphosphate decreased in the order: cacodylate, 2(N-morpholino)ethane sulfonic acid, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and Tris. With the poorer buffers, activity could be increased by the addition of KCl: this effect is not primarily due to an increase in ionic strength. With dGTP as the substrate, but not with dATP or dCTP, activity increased when the concentration of the more active buffers was raised beyond 0.2 M.