A purified protein is in a HEPES buffer at pH 7.0 with 600 mM NaCl. A 1 mL sample of the protein solution is dialyzed against 1.0 L of the same HEPES buffer with 0 mM NaCl. Once the dialysis has come to equilibrium, what is the concentration (in mM) of NaCl in the protein sample

Explanation:

Using the dilution formula to determine the final concentration of NaCl in the protein sample.

However, when dialysis attains equilibrium, it implies that the sample was dialyzed twice, SO:

Now, take the concentration as 2.97 mM

Then:

[NaCl] = 0.01485 mM

i believe the answer is a.