Residue Chemistry for Immobilization — Which functional groups on nonessential amino acid side chains are suitable targets for coupling to supports?

Introduction:
Chemical immobilization leverages reactive side chains on proteins to form covalent links with activated supports. Selecting suitable functional groups affects coupling efficiency, orientation, and activity retention. This question reviews common reactive handles on amino acid residues.

Given Data / Assumptions:

• Focus on nonessential residues for activity to minimize active-site perturbation.
• Supports may be activated with aldehydes, epoxies, NHS esters, or carbodiimide chemistries.
• Coupling conditions are optimized to preserve structure and function.

Concept / Approach:

Carboxyl groups (aspartate, glutamate) couple via carbodiimide chemistry. Amino groups (lysine epsilon-amino, N-terminus) react with aldehyde or NHS-activated supports. Phenolic hydroxyl (tyrosine), aliphatic hydroxyl (serine, threonine), sulfhydryl (cysteine), and imidazole (histidine) can participate in specific chemistries or serve as anchoring points through tailored linkers. A broad array of side chains thus offers multiple immobilization pathways.

Step-by-Step Solution:

Verification / Alternative check:

Immobilization protocols across ion-exchange, affinity, and covalent supports routinely exploit these functionalities, confirming their suitability.

Why Other Options Are Wrong:

E contradicts extensive practice; A–C individually represent valid subsets but not the full picture.

Common Pitfalls:

Overcoupling to lysine residues near the active site can reduce activity; use spacers and controlled activation to mitigate.

Final Answer:

All of the above