Question

Provide an example and explain what it means to see multiple proteins in SDS and only be able to detect the protein of interest in western blot.

Provide an example and explain what it means to not see protein in SDS and be able to detect the protein in western blot.

Answer 1

Answer:

- Desired cell/tissue is lysed and then cell lysate is loaded into the well of SDS PAGE gel and then perform the electrophoresis to separate the different types of proteins present in the cell lysate based on their characteristics (size, weight and charge). In a cell/tissue different types/combination of proteins are present. All these proteins are separated. However, their band intensity depends on the presence/expression of proteins in the cell lysate. More protein gives prominent bands than the less content of protein. In western blotting we are using specific polyclonal or monoclonal antibody of desired target. So from the large numbers of bands present in SDS PAGE only one or two desired proteins of antibodies can be used at a time for detection. Hence, in SDS PAGE we are getting so many bands however, in western blotting we are getting bands of protein of interest only. Example- If we lyse the human cell and run on SDS PAGE then we can get large numbers of prominent and fainted bands of proteins (based on the abundance of proteins in the cell lysate). If our aim in western blotting to get the actin then we have to use polyclonal or monoclonal antibody against actin protein and we will get only one band that is of actin protein present in the cell.

Bands of proteins can be visualised after staining of SDS gel by using commessive stain, silver. However, monoclonal or polyclonal antibody used for the detection of protein present in the SDS PAGE. So protein itself is not detected in SDS but by staining (in SDS) or using monoclonal or polyclonal antibody protein can be detected in SDS.