Which statement is NOT correct regarding low-pH elution and aggregation?

Question

BlackTom AI · Accepted Answer

Acidic conditions (low-pH elution) protonate side chains and disrupt stabilizing interactions, increasing the likelihood of partial unfolding and subsequent aggregation.

1. Relevant knowledge points and concepts
- Protein stability depends on ionic interactions, hydrogen bonds, and hydrophobic core packing. pH changes alter protonation states of side chains (e.g., Asp, Glu, His, Lys), which can break salt bridges and hydrogen bonds.
- Partial unfolding exposes hydrophobic patches that drive self-association and aggregate formation.
- Aggregates are problematic for biologics because they can reduce potency, alter pharmacokinetics, and increase immunogenicity, complicating safety and downstream process development.

2. Step-by-step reasoning
- When elution pH is lowered, acidic residues become protonated and basic residue charge balance shifts, destabilizing tertiary structure.
- Destabilization → increased population of partially unfolded species.
- Partially unfolded species expose hydrophobic regions → enhanced intermolecular hydrophobic interactions → nucleation and growth of aggregates.
- Therefore, lowering elution pH tends to increase aggregation risk; small pH changes can have large effects on stability and aggregation propensity.
- Because aggregates pose safety and development problems, avoiding conditions that promote aggregation (including overly low elution pH) is a key process design consideration.

3. Calculations
- No numerical calculations are required for this conceptual question.

4. Why the correct answer is correct
- The statement labeled as the incorrect (NOT correct) choice claims lowering elution pH “usually increases yield without increasing aggregation risk.” This contradicts well-established biophysical behavior: low pH commonly increases aggregation risk even if yield increases. Thus that statement is false.

5. Why the other options are incorrect (i.e., why they are true statements)
- "Small changes in elution pH can adversely affect product stability": true — proteins can be sensitive to small pH shifts.
- "Molecules that elute at low pH tend to form aggregates": true — low-pH exposure promotes unfolding and aggregation.
- "Aggregates can compromise drug safety and complicate downstream development": true — aggregates can be immunogenic and interfere with formulation and analytics.

6. Conclusion
The NOT-correct statement is "Lowering elution pH usually increases yield without increasing aggregation risk," which matches the provided answer.

Which statement is NOT correct regarding low-pH elution and aggregation?单项选择题

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