Calculate protein concentration with the Layne equation from A280 and A260 absorbance, or solve for a missing absorbance value in mg/mL, g/L, or μg/mL.
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Layne Equation Formula
The Layne equation estimates protein concentration from absorbance readings at 280 nm and 260 nm. It corrects the A280 reading for nucleic acid absorbance at A260.
- Protein = protein concentration, calculated in mg/mL as the base unit
- A280 = absorbance at 280 nm
- A260 = absorbance at 260 nm
- 1.55 = Layne equation coefficient for A280
- 0.76 = Layne equation coefficient for A260 correction
To calculate protein concentration, enter A280 and A260. The calculator applies the main Layne equation.
To calculate A280, enter protein concentration and A260. The calculator rearranges the equation to solve for A280.
To calculate A260, enter protein concentration and A280. The calculator rearranges the equation to solve for A260.
Protein concentration can be entered or displayed in mg/mL, g/L, or μg/mL. The calculation is performed in mg/mL, then converted to the selected unit.
Protein Concentration Unit Conversions
| Unit | Equivalent | Conversion to mg/mL |
|---|---|---|
| mg/mL | 1 mg/mL | multiply by 1 |
| g/L | 1 g/L = 1 mg/mL | multiply by 1 |
| μg/mL | 1000 μg/mL = 1 mg/mL | multiply by 0.001 |
Typical A260 and A280 Reading Notes
| Reading pattern | What it can indicate | Effect on Layne result |
|---|---|---|
| A280 is greater than A260 | Protein absorbance is likely dominant | Usually gives a positive protein concentration |
| A260 is high compared with A280 | Nucleic acid absorbance may be significant | The correction lowers the protein estimate |
| A260 is very high | Sample may contain substantial DNA or RNA | The equation may return a low or negative value |
Example Problems
Example 1: Calculate protein concentration
Suppose A280 = 0.850 and A260 = 0.300.
The protein concentration is 1.0895 mg/mL.
Example 2: Calculate A280
Suppose protein concentration = 1.200 mg/mL and A260 = 0.250.
The A280 value is 0.8968.
FAQ
What does the Layne equation measure?
The Layne equation estimates protein concentration from ultraviolet absorbance readings. A280 is mainly associated with protein absorbance, while A260 is associated with nucleic acids. The equation subtracts a correction based on A260 to reduce the effect of nucleic acid contamination.
Why can the result be negative?
A negative result can happen when the A260 correction is larger than the A280 protein signal. In the formula, this means 0.76 times A260 is greater than 1.55 times A280. A negative concentration is not physically meaningful. It usually means the sample has high nucleic acid absorbance, the absorbance readings are not suitable, or the blanking and dilution steps should be checked.
Are mg/mL and g/L the same for this calculation?
Yes. For protein concentration, 1 mg/mL equals 1 g/L. If you select μg/mL, the calculator converts between μg/mL and mg/mL using 1000 μg/mL = 1 mg/mL.
