The characterization of soybean oil body integral oleosin isoforms and the effects of alkaline pH on them.

Oil body, an organelle in seed cell (naturally pre-emulsified oil), has great potentials to be used in food, cosmetics, pharmaceutical and other applications requiring stable oil-in-water emulsions. Researchers have tried to extract oil body by alkaline buffers, which are beneficial for removing contaminated proteins. But it is not clear whether alkaline buffers could remove oil body integral proteins (mainly oleosins), which could keep oil body integrity and stability. In this study, seven oleosin isoforms were identified for soybean oil body (three isoforms, 24 kDa; three isoforms, 18 kDa; one isoform, 16kDa). Oleosins were not glycoproteins and 24 kDa oleosin isoforms possessed less thiol groups than 18 kDa ones. It was found that alkaline pH not only removed contaminated proteins but also oleosins, and more and more oleosins were removed with increasing alkaline pH.

Solubilization of proteins in extracted oil bodies by SDS: a simple and efficient protein sample preparation method for Tricine-SDS-PAGE.

A simple and efficient method for preparing Tricine-SDS-PAGE protein sample of extracted oil bodies (OBs) was supplied: OB suspension was vortexed with SDS buffer (pH 6.8) for 2 min at room temperature with SDS/protein of 1.52/1(w/w), which could be analyzed by Tricine-SDS-PAGE after simple treatments (dilution and 2-mercaptoethanol). At SDS/protein of 1.52/1, about 95% of proteins in soybean OB suspension were solubilized, whereas residual 5% of proteins were weakly bound to SDS-destroyed OBs; proteins in destroyed OBs might be further solubilized by SDS in the gel and cathode buffer of Tricine-SDS-PAGE, causing about 99% of proteins in soybean OB suspension recover on Tricine-SDS-PAGE gel, which was better than acetone (89%) and diethyl ether (96%) harvested protein samples. Higher or lower SDS/protein was unbeneficial for protein solubilization from OBs. Additionally, the above method was also better than organic solvent method for peanut, sesame, and rapeseed OB suspensions.