Question

Below are data from a protein purification:

Which purification step has the least impact on target protein purity? Why?

Protein purification	Fraction volume(ml)	Total protein (mg)	Activity (units)	Specific activity (unit/mg)
Step1	1400	10000	100000	10
Step 2	280	3000	96000	32
Step 3	90	400	80000	200
Step 4	80	100	24000	240
Step 5	6	3	21000	7000

Answer 1

Based on the given data:

Purification	Fraction volume(ml)	Total protein (mg)	Activity (units)	Specific activity (unit/mg)
Step1	1400	10000	100000	10
Step 2	280	3000	96000	32
Step 3	90	400	80000	200
Step 4	80	100	24000	240
Step 5	6	3	21000	7000

The step that has the least impact on protein purity is the Step4. This is because there is no considerable or significant increase in the protein specific activity from Step 3 (200 units/mg) to Step 4 (240 units/mg).

In all other steps, there is a significant improvement in protein specific activity.