Protein
Protein yield
Turn a concentration and a volume into total protein, then track how much you kept. Give a starting amount to get percentage recovery through a purification step, or a culture volume to get yield per litre for comparing expression between runs.
Recovery and yield
Total protein is concentration times volume. Recovery compares it to the amount you started a step with, so it tracks losses through purification. Yield per litre divides the total by the culture volume for an expression figure you can compare between runs.
Formula
total = concentration × volume; recovery = total ÷ starting × 100
- concentration
- protein concentration of the fraction, in mg/ml
- volume
- volume of the fraction, in ml
- starting protein
- the amount you began the step with, for recovery
- culture volume
- the expression culture volume, for yield per litre
Worked example
2.5 mg/ml in 4 ml
- concentration 2.5 mg/ml
- volume 4 ml
- starting 20 mg
- Total: 2.5 × 4 is 10 mg.
- Recovery: 10 ÷ 20 is 50 per cent.
Answer 10 mg of protein, 50 per-cent recovery
Common mistakes
- Measuring concentration and starting amount by different assays. A Bradford here and a BCA there do not compare cleanly; recovery only means something when the method is consistent.
- Reading recovery above 100 per cent as real gain. It usually signals an assay or dilution mismatch, or interfering substances, not more protein than you started with.
- Comparing yields per litre across different hosts or media without noting them. The figure is only comparable within a consistent expression system.
Frequently asked
How do I get the concentration?
From an A280 reading with the extinction coefficient, or a colorimetric assay against a standard curve. The a280 and standard curve tools both produce it.
Is this fold purification?
No. Fold purification needs specific activity, which is activity per milligram. This tool tracks total protein and recovery, not activity.
What is a good recovery?
It depends entirely on the step and the protein; there is no universal target. Track it across steps to find where you are losing material.