SDS-PAGE Molecular Weight Estimator

In SDS-PAGE, proteins migrate through a gel based on size — and the SDS-PAGE Molecular Weight Estimator translates that migration distance into an estimated protein mass. Enter your protein's migration distance, total gel length, and acrylamide concentration, then select a reference protein standard to get the estimated molecular weight in kDa. Secondary outputs include the Rf value, confidence level, and optimal size range for your gel conditions.

cm

Distance migrated from loading wells to protein band

cm

Total running distance of the gel

V

Voltage used during electrophoresis

min

Duration of electrophoresis run

Results

Estimated Molecular Weight

--

Relative Front (Rf) Value

--

Confidence Level

--

Optimal Size Range

--

Results Table

More Biology Tools

Frequently Asked Questions

How accurate is SDS-PAGE molecular weight estimation?

SDS-PAGE MW estimation is typically accurate within 5-10% for globular proteins between 10-200 kDa. Accuracy depends on gel concentration, reference standards, and protein characteristics.

What gel concentration should I use for my protein?

Use 8-10% for large proteins (>100 kDa), 12-15% for medium proteins (20-100 kDa), and 15-20% for small proteins (<20 kDa). Higher concentrations provide better resolution for smaller proteins.

Why might my protein migrate differently than expected?

Unusual migration can result from protein modifications, high charge density, incomplete denaturation, or binding to SDS molecules. Glycoproteins and membrane proteins often show anomalous migration.

What are the best reference protein standards to use?

Use broad-range standards (10-250 kDa) for unknown proteins, or choose specific ranges based on expected size. Include at least 5-7 standards spanning your protein's expected molecular weight.

How do I calculate the Rf value for my protein?

Rf value = migration distance of protein / total gel length. This normalized value allows comparison between different gels and is used in standard curve calculations.

What factors affect protein migration in SDS-PAGE?

Migration is primarily determined by molecular weight, but gel concentration, crosslinking ratio, voltage, temperature, and buffer conditions also influence separation quality and band sharpness.

Can I estimate molecular weight without protein standards?

It's not recommended. Protein standards are essential for accurate MW determination as migration patterns vary between gels, batches, and running conditions. Always include appropriate molecular weight markers.