Estimate protein molecular weight from SDS-PAGE gel migration distance using standard curves and reference proteins
Estimated Molecular Weight
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Relative Front (Rf) Value
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Confidence Level
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Optimal Size Range
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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.
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.
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.
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.
Rf value = migration distance of protein / total gel length. This normalized value allows comparison between different gels and is used in standard curve calculations.
Migration is primarily determined by molecular weight, but gel concentration, crosslinking ratio, voltage, temperature, and buffer conditions also influence separation quality and band sharpness.
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.