Trends during a successful protein purification scheme: Which changes do you typically expect as purification proceeds?

Introduction / Context:
Protein purification aims to enrich the target relative to contaminants. Tracking total activity, total protein, specific activity, and yield at each step reveals progress and efficiency.

Given Data / Assumptions:

• Specific activity = units per mg protein.
• Each step removes contaminants but may lose some target.
• Analytical checks include SDS-PAGE and activity assays.

Concept / Approach:
As impurities are removed, the denominator (total protein) drops faster than the numerator (activity) for a good protocol, so specific activity rises. Also, chromatography and fractionation reduce the number of proteins present. Total yield often declines somewhat due to inevitable losses.

Step-by-Step Solution:
Start with crude lysate: low specific activity, many proteins.Apply fractionation/columns: contaminants removed, target concentrated.Observe: specific activity up; band complexity on SDS-PAGE down.

Verification / Alternative check:
Purification tables show rising specific activity and decreasing total protein across steps, with yield tracked to ensure acceptable losses.

Why Other Options Are Wrong:

• Specific activity decreases: Indicates poor or damaging procedures.
• Total yield always increases: Unrealistic; losses occur during handling.

Common Pitfalls:
Equating high yield with purity; over-optimizing for yield can sacrifice purity and vice versa.

Final Answer:
Both (a) and (c).