Silver staining of human salivary proteins following two‐dimensional electrophoresis using either protein denaturing or non‐denaturing conditions

The proteins of human whole saliva have been detected by either silver or Coomassie Brilliant Blue R‐250 staining following two‐dimensional electrophoresis using either protein denaturing or non‐denaturing conditions. The high resolution protein denaturing technique revealed over 600 polypeptides and the non‐denaturing technique over 200 proteins in 50 μl of unconcentrated saliva. Silver staining enhances (50–100 fold) detection of the majority of these salivary components and reveals (as clear spots) both polypeptide and proteins not detected with Coomassie Brilliant Blue R‐250. Nevertheless, optimal silver staining of proteins (non‐denaturing conditions) requires pre‐equilibration of the gels in aqueous sodium dodecyl sulphate. In contrast, Coomassie Brilliant Blue R‐250 reveals diffusely staining pink zones not detected by silver staining. The possible nature of salivary components demonstrating unusual staining characteristics is discussed.