What happens to hydrophobic proteins when the salt concentration decreases?

When the salt concentration decreases, hydrophobic proteins tend to be less stabilized in solution. Typically, in protein purification processes, such as those often used for isolating GFP, ionic strength plays a crucial role in protein solubility and interactions.

In low salt conditions, the repulsion between water molecules and hydrophobic regions of the proteins becomes more favorable, causing these proteins to become less soluble in the aqueous solution. Instead, they tend to aggregate and precipitate out of solution or stick together. This behavior is particularly significant for hydrophobic proteins, which seek to minimize their exposure to water.

As a result, under low salt concentrations, hydrophobic proteins can tend to coalesce and may appear in a more concentrated and purified form, which aligns with the understanding of their behavior in a protein purification context. This purification step is often key to isolating GFP from other cellular components, as it allows for the selective separation of the target protein based on its hydrophobic properties.