Data analysis · Beta · Free Verbex lab tool
BCA and Bradford Protein Assay Calculator
Paste your BSA standards and samples from the plate reader. Verbex subtracts the blank, fits the standard curve, gives each sample's protein concentration, and works out how much to load for your western blot.
Protein assay: BCA, cell lysates
Curve passes: 8 of 8 standards within limits. Working range 25–2000 µg/mL.
Fit: Quadratic, unweighted, R² 0.9998 (y = 0.001646 + 0.001189·x − 0.0000001647·x²).
Blank: mean 0.051. Blank subtracted from every well and kept in the fit as the zero standard, as in the kit instructions and instrument software.
| Standard (µg/mL) | Mean response | CV | Back-calculated | Recovery | Result |
|---|---|---|---|---|---|
| 25 | 0.0305 | 2.6% | 24.34 | 97.4% | pass |
| 125 | 0.144 | 2.2% | 121.7 | 97.4% | pass |
| 250 | 0.2945 | 1.8% | 255.3 | 102.1% | pass |
| 500 | 0.5555 | 1.0% | 500.3 | 100.1% | pass |
| 750 | 0.805 | 1.0% | 754.2 | 100.6% | pass |
| 1000 | 1.026 | 0.8% | 999.7 | 100.0% | pass |
| 1500 | 1.408 | 0.9% | 1490 | 99.3% | pass |
| 2000 | 1.725 | 1.1% | 2006 | 100.3% | pass |
| Sample | Dilution | Mean response | CV | Concentration (µg/mL) | Result |
|---|---|---|---|---|---|
| Lysate A | 1:5 | 0.6575 | 0.7% | 3008 | in range |
| Lysate B | 1:5 | 0.355 | 1.4% | 1552 | in range |
| Lysate C | neat | 1.909 | 0.7% | > 2000 | above range: dilute further |
Loading: 20 µg per lane, 20 µL final volume
| Sample | Concentration (µg/mL) | Sample (µL) | Buffer (µL) | Note |
|---|---|---|---|---|
| Lysate A | 3008 | 6.649 | 13.35 | |
| Lysate B | 1552 | 12.88 | 7.115 | |
| Lysate C | — | — | — | no concentration (outside range) |
Limits: Verbex protein-assay defaults (recovery ±15%, ±25% at the lowest and highest standards; replicate CV ≤ 15%; at least 75% and 5 levels passing). No regulatory guideline sets these.
A straight line through the same standards would read these samples up to 12.1% differently; many instruments fit a line for BCA.
Concentrations are relative to the standard protein (usually BSA).
Check: every standard put back through the fitted curve reproduces its mean response ✓
Beta method, checked against published datasets; the choices behind this result are listed with it.
Verbex Lab Tools · Protein assay v0.1.0-beta · 2026-10-15 15:50 UTC · verify before use
- Lysate C reads above the ULOQ (2000 ug/mL); dilute it further and rerun.
How it is calculated
Every number shows its work.
Verbex subtracts the mean blank from every standard and sample, as the BCA and Bradford kit procedures do, then fits a quadratic curve to the blank-corrected standards. The Pierce BCA user guide notes that a quadratic or best-fit curve is more accurate than a straight line; a line or a 4PL is one option away.
Each standard is read back through the curve. By default it passes if it recovers within ±15% of its concentration (±25% at the lowest and highest standards) with replicate CV of 15% or less, and the curve passes if at least 75% of standards and 5 levels pass. No regulatory guideline sets these limits for protein assays, so they are Verbex defaults you can change; the result always states which limits it used.
Samples are read only between the lowest and highest passing standards, then multiplied by their dilution factor; anything outside is reported as below or above range. With a loading target, each sample's volume is the protein mass divided by its concentration, and buffer brings every lane to the same volume.
Concentrations are relative to the standard protein, usually BSA: proteins differ in how strongly they react. This is a beta, checked against published data: 9 published BCA, Bradford, Lowry and Pierce 660 datasets reproduce within about 1% with matching settings. Treat results as checked.
Use it from your AI assistant
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