The purification data for an enzyme is given below:
| Step | Process | Volume (ml) | Total protein (mg) | Total activity (Units) | Specific activity (Units/mg) |
|---|---|---|---|---|---|
| P | Cell-free extract | 17 | 177 | 102 | 0.58 |
| Q | Q-Sepharose | 14 | 18.8 | 72 | 3.83 |
| R | Phenyl Sepharose | 26 | 9.2 | 45 | 4.89 |
| S | Sephacryl S-200 | 7 | 4.1 | 30 | 7.32 |
Q.50 The fold purification for each step is
Fold Purification Calculation in Enzyme Purification Table
In enzyme purification experiments, fold purification indicates how much purer an enzyme becomes
after each purification step. It is calculated using specific activity, which is defined as
enzyme activity per milligram of protein.
Given Purification Data
| Step | Process | Specific Activity (Units/mg) |
|---|---|---|
| P | Cell-free extract | 0.58 |
| Q | Q-Sepharose | 3.83 |
| R | Phenyl Sepharose | 4.89 |
| S | Sephacryl S-200 | 7.32 |
Formula for Fold Purification
Fold Purification =
Specific activity at a given step / Specific activity of crude extract
The cell-free extract (Step P) is taken as the reference, so its fold purification is always 1.
Step-by-Step Calculation
Step P (Cell-free extract)
0.58 / 0.58 = 1
Step Q (Q-Sepharose)
3.83 / 0.58 ≈ 6.6
Step R (Phenyl Sepharose)
4.89 / 0.58 ≈ 8.4
Step S (Sephacryl S-200)
7.32 / 0.58 ≈ 12.6
Correct Fold Purification Values
| Step | Fold Purification |
|---|---|
| P | 1 |
| Q | 6.6 |
| R | 8.4 |
| S | 12.6 |
Correct Answer
Option (C): P-1, Q-6.6, R-8.4, S-12.6
Conclusion
Fold purification is calculated by dividing the specific activity of each purification step by that of the crude extract.
Using this method, Option (C) is the correct answer.
