While studying expression of a single protein from different cell sources by western blot technique how to calculate changes in the expression of protein by normalization?
It is not always easy. Estimation of the relative amount of the proteins in cellular lysates using a housekeeping protein (actin, tubulin, etc) as a standard might be a good choice. However, if you are going to estimate the absolute amount of the protein or released protein in cell supernatant you may use other standard. Related recombinant protein (produced in bacteria and recognized by your serum) or a related commercial protein with a known concentration, or even a peptide with an epitope recognized by the antibody might be used for calibration. Peptides, for the simplicity of transfer, should not be less than 25 residues long.