Purification and characterization of selenium-containing phycocyanin from selenium-enriched Spirulina platensis

Abstract: A fast protein liquid chromatographic method for purification of selenium-containing phycocyanin (Se-PC) from selenium-enriched Spirulina platensis was described in this study. The purification procedures involved fractionation by ammonium sulfate precipitation, DEAE-Sepharose ion-exchange chromatography and Sephacry S-300 size exclusion chromatography. The purity ratio (A 620/A 280) and the separation factor (A 620/A 655) of the purified Se-PC were 5.12 and 7.92, respectively. The Se concentration of purified Se-PC was 496.5μg g−1 protein, as determined by ICP-AES analysis. The purity of the Se-PC was further characterized by UV–VIS and fluorescence spectrometry, SDS–PAGE, RP-HPLC and gel filtration HPLC. The apparent molecular mass of the native Se-PC determined by gel filtration HPLC was 109kDa, indicating that the protein existed as a trimer. SDS–PAGE of the purified Se-PC yielded two major bands corresponding to the α and β subunits. A better separation of these two subunits was obtained by RP-HPLC. Identification of the α and β subunits separated by SDS–PAGE and RP-HPLC was achieved by peptide mass fingerprinting (PMF) using MALDI-TOF-TOF mass spectrometry. [Copyright &y& Elsevier]