The leucine side chain is hydrophobic, meaning it repels water. Therefore, it would most likely be found in the following locations in a protein dissolved in water:

* Interior of the protein: The hydrophobic side chains of leucine would cluster together in the interior of the protein, away from the surrounding water molecules. This minimizes the disruption of the water structure caused by the hydrophobic side chains.

* On the surface of the protein, in contact with other hydrophobic residues: Leucine could also be found on the surface of the protein, but only if it interacts with other hydrophobic residues, forming a hydrophobic patch. This reduces the exposure of the hydrophobic side chain to water.

In summary: Leucine, being hydrophobic, would be found in the interior of a protein or on the surface in close proximity to other hydrophobic residues, minimizing its exposure to water.