What effect has changing pH and salt concentration on protein complexes?

Question

I'm struggling to find peer reviewed literature that explains the effect of changing the pH and the salt concentration on protein/protein complexes in solution. What effect does the pH and the salt concentration have and what is the physical basis behind this?

Answer 1

Hi, By changing pH and salt concentrations you will hinder the ability of protein complexes to form salt bridges. Many proteins form both intra (same protein) and inter (2 different proteins) chain di-sulfide connections. These connections are mainly formed from the amino acid cysteine complexing with a neighboring cysteine, thus forming 2 cystine's. Cysteine normally has a free SH group but in the disulfide bond form it looks like Protein 1-S-S- Protein 2 where the S's symbolize the two sulfurs forming a bond.

Disulfide bonds are important for proteins tertiary structure, as they stabilize the arrangement. They also serve an important role in the proper folding of a protein. By adding salt concentration or changing the pH this will cause disulfide bonds to break as they react with the salt solution or free hydrogen ions (changing pH).