Why might proteins have altered solubility at different pH levels?

Proteins are made up of amino acids, each with their own side chains that can be charged or uncharged depending on the pH of the surrounding environment. The solubility of a protein in a solution greatly depends on its net charge, which changes as the pH varies.

At different pH levels, the ionizable groups in the protein can either gain or lose protons (H+ ions). For instance, if the pH is lowered (more acidic), acidic side chains may remain protonated and carry a negative charge, while basic side chains may be protonated and carry a positive charge. Conversely, if the pH is raised (more basic), acidic groups may lose their protons, becoming neutral, while basic groups may lose protons and become negatively charged.

This dynamic change in the net charge affects how proteins interact with water and other molecules. At certain pH levels, a protein may be more positively or negatively charged, which can increase or decrease its solubility due to electrostatic interactions: similar charges repel and opposite charges attract. When proteins are at their isoelectric point (the pH at which they have a net charge of zero), solubility tends to be lowest because there is minimal repulsion among