Salt for annealing oligos - (Aug/22/2007 )
I wonder why is it important to have at least 50mM NaCl when annealing oigos?
The reason is that the phosphate backbone of DNA is negatively charged so single-standed DNA, such as your oligos, will slightly repel each other, preventing or at least inhibiting annealling. In solution, NaCl dissociates to give Na+ and Cl-. The Na+ associates with the negatively charged phosphate groups, neutralizing the charge and allowing the strands to come together.
thank you, Nick!