Gly34-Glu251. N-terminal His-tag. Calculated MW: 26.0 kDa Observed MW (SDS-PAGE): 33 kDa Possible reasons why the actual band size differs from the predicted band size: 1. Splice variants. Alternative splicing may create different sized proteins from the same gene. 2. Relative charge. The composition of amino acids may affect the charge of the protein. 3. Post-translational modification. Phosphorylation, glycoslyation, methylation etc. may affect the band size. 4. Post-translational cleavage. Many proteins are synthesised as pro-proteins, and then cleaved to give the active form. 5. Polymerisation of the target protein. Dimerisation, multimerisation etc. will increase the band size observed. Recombinant Tissue Factor (TF) is a recombinant protein from Human. It is produced in E. coli using Prokaryotic expression.