Why is the solubility of proteins in water lower at their isoelectronic points?

Proteins have a net positive charge and will repel water at their isoelectronic points, which makes them less soluble in water.

Proteins have a net negative charge and will repel water at their isoelectronic points, which makes them less soluble in water.

Proteins have a zero net charge and will promote protein-protein interactions at their isoelectronic points, which makes them less soluble in water.

Proteins are neutral (pH = 7) and will promote protein-protein interactions at their isoelectronic points, which makes them less soluble in water.