SDS-PAGE: How to Measure Migration Distance When Determining Protein Molecular Weight?

SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) is a common method used to analyze protein size (molecular weight). After conducting an SDS-PAGE experiment, the molecular weight of proteins can be estimated by measuring their migration distance in the gel.

Use image analysis software (such as ImageJ or other analysis software) or a ruler to measure the migration distance of proteins, which is the distance from the sample well to the protein band.

How to estimate protein molecular weight using migration distance:

1. Create a standard curve:

• Perform the SDS-PAGE experiment using a standard protein mixture with known molecular weights.
• Measure the migration distances of these standard proteins and plot a graph of molecular weight versus migration distance. This graph typically appears nonlinear and can be fitted with a curve (e.g., using a log-log plot).

2. Estimate the molecular weight of unknown proteins:

• Measure the migration distance of the unknown proteins.
• Use the previously created standard curve to estimate the molecular weights of these proteins.

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