Protein Loading
Fit your BCA or Bradford standards, read each sample's protein concentration, and get a Western blot loading table with the same µg in every lane.
1 · STANDARD CURVESECTION 05 — CELLS & PROTEIN · 5.2
| STANDARD (µg/mL) | ABSORBANCE · replicates | Remove |
|---|
The 0 µg/mL standard is the blank: its absorbance is subtracted from everything.
2 · SAMPLESABSORBANCE → µg/µL
| SAMPLE | ABSORBANCE · replicates | DIL. × | µg/µL | Remove |
|---|
DIL. ×: how much you diluted the lysate before the assay — 5 for 1:5. Leave 1 if you didn't.
3 · LOADING TABLEEQUAL µg PER LANE
| LANE | SAMPLE | µg/µL | SAMPLE | BUFFER | WATER | TOTAL |
|---|
How to use
- Enter your standards (e.g. BSA for BCA) and their absorbance readings. Several replicates? Type them in one box separated by spaces — they're averaged.
- Keep the 0 µg/mL standard: it's used as the blank. Choose LINEAR or QUADRATIC — pick the one with R² closer to 1 that follows your points.
- Enter each sample's readings, and the dilution if you diluted the lysate before the assay.
- Already know the concentrations? Choose CONCENTRATIONS ALREADY and type them in µg/µL (= mg/mL).
- Set µg per lane, the volume you load per lane, and your sample buffer. The table gives sample, buffer and water for each lane.
- COPY TABLE pastes into Excel or your notebook; PRINT gives a bench sheet.
The formula
| sample conc. | c from the curve × dilution ÷ 1000 (µg/mL → µg/µL) |
| sample vol. | µg per lane ÷ µg/µL |
| buffer | lane volume ÷ X (4X → ¼) |
| water | lane volume − sample − buffer |
Example. 20 µg in 20 µL with 4X buffer, lysate at 2.5 µg/µL: 8 µL sample + 5 µL buffer + 7 µL water.
Good to know
- Free to use. No subscription. Nothing you type leaves your browser.
- Samples that read above the top standard are flagged — dilute them and read again rather than trusting an extrapolated value.
- Add reducing agent to the buffer as your kit says; this tool treats the buffer as one volume.
- Volumes are rounded to 3 significant figures.
Frequently asked
Should I use a linear or quadratic fit for my BCA curve?
Pick the one with R² closer to 1 that follows your points. BCA curves often bend at the top, where a quadratic fits better.
What happens if a sample reads above the top standard?
It is flagged. Dilute the sample and read it again rather than trusting an extrapolated value.
How are the loading volumes calculated?
Sample volume = µg per lane ÷ µg/µL; buffer = lane volume ÷ buffer strength; water makes up the rest. For 20 µg in 20 µL with 4X buffer and lysate at 2.5 µg/µL: 8 µL sample + 5 µL buffer + 7 µL water.
How is the blank handled?
The 0 µg/mL standard is the blank. Its absorbance is subtracted from every standard and sample.