Western blot
A laboratory technique used to detect specific proteins in a sample using antibodies. It separates proteins by size via gel electrophoresis, transfers them to a membrane, and identifies target proteins through antibody binding, commonly used in research, diagnostics, and quality control.
How does a Western blot work?
Western blotting is a multi-step analytical method used to detect specific proteins in a complex mixture. First, proteins are separated by size using sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The separated proteins are then transferred from the gel to a nitrocellulose or polyvinylidene fluoride (PVDF) membrane. The membrane is blocked to prevent non-specific binding, then incubated with a primary antibody specific to the target protein. After washing, a secondary antibody conjugated to an enzyme or fluorophore is added, which binds to the primary antibody. Detection is achieved through chemiluminescence, fluorescence, or colour development, producing a band at the molecular weight of the target protein.
What are the applications of Western blotting?
Western blotting is widely used in molecular biology, biochemistry, and biomedical research to confirm protein expression, assess post-translational modifications, and validate antibody specificity. In clinical and diagnostic settings, it is employed to detect disease markers, such as HIV antibodies or prion proteins. In pharmaceutical and biotech industries, it supports process development, product characterization, and batch consistency testing. It is also used in regulatory submissions to demonstrate identity, purity, and potency of protein-based therapeutics.
What are the limitations of Western blotting?
Despite its specificity, Western blotting has several drawbacks. It is time-consuming, requiring several hours to complete. It demands relatively large sample amounts compared to newer techniques like mass spectrometry. Results can be affected by antibody quality, non-specific binding, and variability in transfer efficiency. Additionally, it is semi-quantitative at best, making precise quantification challenging without proper calibration. However, it remains a gold standard for protein detection in many contexts due to its high specificity and reproducibility.
Related concepts
Western blotting is often used alongside other techniques such as ELISA for high-throughput screening, immunohistochemistry for spatial protein localization, and mass spectrometry for comprehensive protein identification and quantification.