In order to reconstitute nucleosomes, I mixed DNA with histone octomers and set them up for a 16-hour dialysis to go from a NaCl concentration of 2 M to 50 mM. I used SnakeSkin Dialysis Tubing at 3.5 MWCO 33 mm dry as the membrane. Each had 100 µL of sample inside to start (I cut the caps together with the top ring of LoBind tubes, used the underside of the caps to hold the samples, put the wet membrane on top and secured them with the attached ring to trap the liquid). After the 16-hours of buffer exchange, the samples did not look saturated, and I could only extract the same amount of liquid that I had started with across all samples. I tested this out by throwing in a prepared cap with membrane but without any liquid inside and after 16-hours no liquid had penetrated the membrane.

Why was the buffer unable to pass through the membrane? They were all pre-wet with the starting buffer at 2M NaCl, but it is clear that the buffer does not make it through.