Research Note: Integrated proteomic analyses of chicken egg yolk granule.

Chicken egg yolk granules (EYG) were the precipitated component of egg yolk after water dilution and centrifugation. Compared with egg yolk, EYG are rich in proteins, phospholipids, and minerals. In this study, an integrated proteomic analysis was carried out to in-depth mapping of the proteome, phosphoproteome, and N-glycoproteome of EYGs. After hydrolysis of the EYG total protein, the hydrolyzed peptides or the enriched phosphopeptides/glycopeptides were identified by liquid chromatography-tandem mass spectrometry. A total of 125 phosphorylation sites from 36 phosphoproteins and 244 N-glycosylation sites from 100 N-glycoproteins were identified in EYG. All 3 vitellogenins (precursors of egg yolk high-density lipoprotein) were heavily phosphorylated and N-glycosylated, of which 37 phosphorylation sites and 32 N-glycosylation sites were identified on vitellogenins-2. A Total of 30 N-glycosylation sites were identified on apolipoprotein-B (precursor of egg yolk low-density lipoprotein), but no phosphorylation site was identified. These phosphorylation and N-glycosylation of EYG proteins provide new insights for understanding the assembly structure and functional characteristics of EYG, thus contributing to its development and utilization.

Research Note: Aggregation-depolymerization of chicken egg yolk granule under different food processing conditions.

Chicken egg yolk granule is a natural micro-nano aggregate in egg yolk, and its assembly structure varies under different processing conditions. In this study, the effects of NaCl concentration, pH, temperature, and ultrasonic treatment on the properties and microstructure of yolk granule were determined. The results showed that ionic strength (above 0.15 mol/L), alkaline environment (pH 9.5 and 12.0), and ultrasonic treatment induced the depolymerization of egg yolk granule; while freezing-thawing, heat treatment (65°C, 80°C, and 100°C), and mild acidic pH (pH 4.5) induced the aggregation of yolk granule. Scanning electron microscopy observation showed the assembly structure of yolk granule varied with different treatment conditions and confirmed the aggregation-depolymerization of yolk granule under different conditions. Correlation analysis showed that turbidity and average particle size are the 2 most critical indicators that can reflect the aggregation structure of yolk granule in solution. The results are important for understanding the changing mechanism of yolk granule during processing, and provide important information for the applications of yolk granule.

Ovomucin may be the key protein involved in the early formation of egg-white thermal gel.

Clarification of the mechanism of heat-induced gel formation by proteins under natural food systems could provide important references for the regulation of food texture. In the present study, the proteins involved in the early stage (heating at 72 °C for 8 min) of egg-white thermal gel (EWG) formation were studied quantitatively through comparative proteomic analysis. We discovered that the abundance of ovalbumin and ovomucoid increased significantly (p < 0.01), whereas that of ovotransferrin, lysozyme, ovomucin (mucin 5B and mucin 6) decreased significantly (p < 0.01), in the supernatant of EWG. If the initial interaction of egg white proteins was altered by ultrasonic pretreatment, the abundance of ovomucin and lysozyme in the supernatant of EWG increased, and was accompanied by the change from a solid gel to a fluid gel. Based on these results, we hypothesize that ovomucin has a key role in the formation and regulation of EWG properties.

Effects of high-intensity ultrasonic (HIU) treatment on the functional properties and assemblage structure of egg yolk.

The effects of high-intensity ultrasonic (HIU) treatment on the functional properties of egg yolk were studied in the present work. After HIU treatment, the emulsifying, foaming and gel properties of the egg yolk solution significantly increased, but the foam stability decreased. SDS-PAGE results showed that there was no obvious change in the protein bands of egg yolk, indicating that the yolk proteins did not undergo covalent crosslinking or degradation. HIU treatment enhanced the zeta potential of egg yolk components in solution and increased the free sulfhydryl content of egg yolk proteins. Moreover, the particle size distribution of egg yolk components in solution changed markedly, and these changes demonstrated that HIU treatment caused the aggregation of yolk low-density lipoprotein and the partial dissociation of yolk granules. These results revealed that HIU treatment could change the aggregation of yolk components, which in turn could influence the solution characteristics of egg yolk, finally resulting in changes to the functional properties of egg yolk.

Melongenaterpenes A-L, Vetispirane-Type Sesquiterpenoids from the Roots of Solanum melongena.

Melongenaterpenes A-L (1-12), 12 new sesquiterpenoids with rare spiro[4.5]decane skeletons, were isolated from the roots of Solanum melongena. Their 2D structures and relative configurations were determined based on NMR and HRESIMS data. The absolute configuration of melongenaterpene A (1) was defined by X-ray crystallographic analysis. The absolute configurations of the remaining compounds were determined by comparison of their NMR data with 1 and consideration of the biosynthetic pathway. This is the first report of the crystal structure of a vetispirane-type sesquiterpenoid. None of the compounds exhibited cytotoxic activity against the three human cancer cell lines HepG2, HeLa, and MCF-7.

Proteomics Research on the Protective Effect of Mangiferin on H9C2 Cell Injury Induced by H2O2.

Cardiovascular disease is one of the leading causes of morbidity and mortality worldwide. Mangiferin is a natural glucosylxanthone with antioxidant and anti-inflammatory properties, which has been confirmed to protect cardiac cells from myocardial infarction and myocardial ischemia reperfusion injury (MIRI); however, the underlying mechanism is still unclear. As oxidative stress is a major pathogenesis of MIRI, an H9C2 cell injury induced by hydrogen peroxide (H2O2) was established to simulate MIRI in vitro. Herein, the protective effect of mangiferin against MIRI was evaluated and the isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics was applied to explore the underlying molecular mechanism. In this research, mangiferin markedly ameliorated the oxidative imbalance by increasing the antioxidative capacity of the H9C2 cell. Moreover, proteomics analysis revealed that mangiferin pretreatment brought twenty differently-expressed proteins back to normal, most of which were related to glucose and fatty acid metabolism. Glycolysis, citrate cycle, and fatty acid degradation pathways were highlighted by Kyoto Encyclopedia of Gene and Genomes (KEGG) analysis. Western blot validation of six cardiac metabolism-related proteins were consistent with the proteomics analysis. Taken together, mangiferin protected the cardiomyocytes from MIRI by enhancing the antioxidant capacity and increasing the activities of glycolysis, citrate cycle, and fatty acid degradation pathways.