Final answer:
Glutaraldehyde is the chemical used to couple a ligand to resin that reacts with hydroxyl groups in agrose.
Step-by-step explanation:
The chemical used to couple a ligand to resin that reacts with hydroxyl groups in agrose is glutaraldehyde.
Glutaraldehyde is commonly used in biochemistry to crosslink proteins, as it reacts with hydroxyl groups in proteins.
For example, when glutaraldehyde reacts with hydroxyl groups in agrose, it forms crosslinks between the molecules, allowing the ligand to be attached securely to the resin.