• Decreased solubility --> as more hydrophobic groups are exposed to water
  
• Aggregation of proteins --> hydrophobic groups of proteins interact with each other. Aggregates inhibit the refolding.
• Increased accessibility of peptide bonds to proteolytic enzymes, increased degradability
• Loss of biological activity --> biological activity depends on precise conformation of protein, so change in conformation results in a lower biological activity. Also called, enzyme activity
• Increased reactivity --> due to unfolding reactive groups become exposed. Exposure of thiol group (-SH), reshuffling can take place.

• pH closed to pI --> aggregates (by hydrophobic groups) --> solubility decreases
  
• pH far from pI --> electrostatic repulsion --> soluble
• Hydrophobic amino acid residues --> solubility lower
• Hydrophilic amino acid residues --> solubility higher

The solubility of proteins is the balance between repulsive electrostatic interactions and attractive hydrophobic interactions between proteins.

• Low salt concentration (10-20 mM) --> can increase the solubility, at pI --> salting in effect, charged groups are solvated --> interaction with solvent increased
  
• Medium salt concentration (10 mM - 500 mM) --> DLVO theory --> Na+ will screen the charged groups, less repulsion
• Very high salt concentration (~5%) --> solubility decreases --> salting out effect --> purification of proteins by adding ammonium sulphate to a mixture of soluble proteins, after which proteins start to precipitate.