Role of SDS, β-mercaptoethanol, bromophenol blue and glycerol in western blot sample buffer or laemmli buffer

β-mercaptoethanol is a reducing agent - it reduces any disulphide bridges that are holding the protein tertiary structure.

SDS -Sodium dodecyl sulphate is an anionic detergent that strongly binds to proteins and denatures it. On average one SDS molecule binds for every 2-amino acid residues. SDS molecules bound along the polypeptide chain gives the proteins a net negative charge. The treatment opens up the proteins into a rod-shaped structure.

Bromophenol blue is an ionisable tracking dye. The dye helps in monitoring the electrophoretic run. Otherwise, the proteins that run cannot be tracked and consequently the proteins might run off into the buffer at the bottom.

Glycerol or sucrose are used to give the sample solution density (add weight to the sample). This allows the sample to settle easily when loaded into the well.