Detection and quantification of selenium in proteins by means of gel electrophoresis and electrothermal vaporization ICP-MS

Abstract

A method for the separation of selenium-containing proteins and subsequent detection and quantification of selenium was developed. First, the proteins are fractionated by means of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE); subsequently, the bands of the gel, containing the proteins, are analyzed by electrothermal vaporization (ETV)-ICP-MS to detect and quantify selenium. External standardization with the use of an internal reference (Te) was applied. A detection limit of ca. 40 pg Se per band and a recovery of ca. 98% were obtained. A single measurement is accomplished in less than 4 min and thus a gel lane after a separation of ca. 1.5 h, can be entirely analyzed with ETV-ICP-MS in 3.5 h. If limited to 10 bands, a gel lane is analyzed in 2 h (calibration included). The analysis is directly carried out on the stained gel, without blotting, which makes the analysis even more practical. This method was optimized using the selenoprotein glutathione peroxidase as model. Then, it was applied to the fractionation of proteins from a selenium–yeast candidate reference material. The reconstructed Se electropherograms are presented and compared with the stained gels. The major advantages of this method are the high resolution of the protein fractionation and the straightforward quantification of selenium.