Western Blotting: Principle, Procedure and Applications

Definition: Technique for detecting specific proteins separated by electrophoresis by use of labelled antibodies.
  • Devised by Towbin in 1979
  • The term “Western” has no scientific significance just a misnomer.
  • Principle: antigen antibody interaction, an immunodetection method
Summary of Procedure:
1. Extract and purify protein from cells
2. Separated by SDS-PAGE (Sodium dodecyl sulphate-PolyAcrylamide Gel Electrophoresis)
Function of SDS: SDS is an anionic detergent. Here it denatures protein and impart an overall negative charge. Therefore separation is based on size

Western blotting and role of SDS
3. Transfer proteins from gel to nitrocellulose paper
4. Blocking nonspecific antibody sites on the nitrocellulose paper with bovine serum albumin (BSA) or milk powder
5. Probing electroblotted proteins with primary antibody
6. Washing away nonspecifically bound primary antibody
7. Detecting bound antibody by horseradish peroxidase-anti-Ig conjugate or formation of a diaminobenzidine (DAB) precipitate, radiolabelling or use of fluorescently labelled secondary antibody.
8. Autoradiography or photographing or fluorescence detection
Western blotting protein bands and difference in protein expression
Different samples of equal quantity are loaded in each lane. From the blot it is clear that protein expression (40,000 MW) is more in lane 4 and 5.
  • Highly sensitive method to detect a specific protein even in very low quantity.
  • Used in clinical diagnosis
  • Quantifying a gene product (gene expression studies)


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  1. sowmya gurumoorthy2 October 2015 at 20:13

    I'm studying biotechnology. It is very useful for my studies

  2. These notes are Very helpful for me...thanks!

  3. helpful for tommorow's exam :D

  4. very good. well done!

  5. it was very educating and understanding,thank you

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