Separation and detection of selenium-containing proteins in human serum

Selenium-containing proteins or their subunits in human serum were separated and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the amount of selenium in each protein band was determined by HPLC with a fluorescence detector after derivatization with 2,4-diaminonaphthalene (DAN). This procedure provides a detection limit of 0.06 ng in a linear range of 0-1.5 ng. A protein is defined as a selenium-containing protein if its mean Se content exceeds twice the detection limit (0.12 ng) and twice the standard deviation of three replicates in sample determination. At least 4 selenium-containing bands with apparent molecular masses of 57-74, 46-56, 40-42 and 21-22 kDa could be detected from human serum collected from 4 volunteers.