Effects of High Pressure Processing and Thermal Treatment on the Interaction between α-Lactalbumin and Pelargonium-3-Glucoside.

In this study, high pressure processing (HPP) and thermal treatment were comparatively evaluated by examining their impacts on the binding behavior and interaction between α-lactalbumin (α-La) and pelargonium-3-glucoside (P3G) under pH values of 6.0, 7.4, and 8.0. The methods of circular dichroism spectroscopy, fluorescence quenching, dynamic light scattering, and molecular simulation were used to characterize the effects of processing-induced changes in protein structure, size distribution, binding site conformation, and residue charges on their binding characteristics between them. The results indicated that the thermal treatments significantly increased the quenching constants of the complex at pH 7.4/8.0 and 60/80 °C, as well as the accessible fraction of protein at pH 8.0/80 °C. Both HPP and thermal treatments increased the random coil content and showed limited effects on the α-helix and ß-sheet contents of α-La and caused the aggregation of the complex to varying degrees. Molecular dynamic simulation and docking analyses revealed that the binding site of the complex did not change under different processing conditions, but the solvent-accessible surface area varied under different conditions.

Insight into the mechanism of high hydrostatic pressure effect on inhibitory efficiency of three natural inhibitors on polyphenol oxidase.

The development of natural inhibitors of polyphenol oxidase (PPO) is crucial in the prevention of enzymatic browning in fresh foods. However, few studies have focused on the effect of subsequent sterilization on their inhibition efficiency. This study investigated the influence and mechanism of high hydrostatic pressure (HHP) on the inhibition of PPO by epigallocatechin gallate (EGCG), cyanidin-3-O-glucoside (C3G), and ferulic acid. Results showed that under the conditions of 550 MPa/30 min, the activity of EGCG-PPO decreased to 55.92%, C3G-PPO decreased to 81.80%, whereas the activity of FA-PPO remained stable. Spectroscopic experiments displayed that HHP intensified the secondary structure transformation and fluorescence quenching of PPO. Molecular dynamics simulations revealed that at 550 MPa, the surface interaction between PPO with EGCG or C3G increased, potentially leading to a reduction in their activity. In contrast, FA-PPO demonstrated conformational stability. This study can provide a reference for the future industrial application of natural inhibitors.

Assessing the influences of ß-glucan on highland barley starch: Insights into gelatinization and molecular interactions.

Developing highland barley products is complex, possibly due to the presence of ß-glucan in highland barley. This study aims to investigate the impact of ß-glucan on the physicochemical properties, microstructure, and molecular interactions of highland barley starch (HBS) during gelatinization and aging. Increasing the ß-glucan content significantly reduced peak viscosity, setback viscosity, and breakdown viscosity, indicating altered gelatinization behavior. The ß-glucan content increase caused a significant drop in peak viscosity. With 20% ß-glucan addition, it reduced by 883 mPa·s, nearly 38%. Rheological analysis showed a transition from a solid-like to a liquid-like texture or quality, ultimately leading to a shear-thinning behavior. Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) confirmed the interaction between HBS and ß-glucan via intermolecular hydrogen bonding, promoting the formation of double helical structures in starch. These findings provide a deeper understanding of the role of ß-glucan in the processing of highland barley, highlighting its influence on the starch's properties.

Multispectroscopic and computational simulation insights into the inhibition mechanism of epigallocatechin-3-gallate on polyphenol oxidase.

Polyphenol oxidase (PPO)-mediated enzymatic browning occurs in fruit, vegetables and aquatic products and causes huge economic losses every year. In this study, epigallocatechin-3-gallate (EGCG) displayed high affinity for and efficient inhibitory capacity against PPO. To explore the inhibition mechanism, multispectroscopic methods and computational simulations were implemented. Initially, EGCG inhibited PPO activity reversibly in a mixed-type manner. Then, the conformation and secondary structure changes of PPO after binding with EGCG were discovered by fluorescence emission spectra and circular dichroism. Molecular docking and dynamic simulation results revealed that EGCG could tightly bind with the binuclear copper domain of PPO through hydrophobic stacking and hydrogen bonds. Moreover, EGCG might act as a linker to interact with different PPO molecules at another binding site. Transmission electron microscopy observation suggested that EGCG induced the aggregation of PPO. Therefore, the inhibition mechanism of EGCG on PPO included competition for catalytic centers and induced aggregation.

Inhibition effect of high hydrostatic pressure combined with epigallocatechin gallate treatments on pectin methylesterase in orange juice and model system.

High hydrostatic pressure (HHP) is currently the most successful non-thermal processing technology for commercial applications, but with a drawback that it is difficult to effectively inactivate the pectin methylesterase (PME), which is critical to the stability of orange juice. In this study, the PME inhibition and mechanism by HHP (600 MPa/10 min) combined with epigallocatechin gallate (HHP-EGCG) treatment were investigated. Firstly, the HHP-EGCG treatment showed enhancement effect on PME inhibition in orange juice, and the samples maintained higher content of water soluble pectin and exhibited higher suspension stability than the HHP treated samples during 13 days of refrigerated storage. Secondly, after HHP-EGCG treatment, further synergistic effect was observed in the phosphate buffer system, and the greatest secondary structure transformation and fluorescence quenching of PME occurred. Finally, molecule docking suggested that EGCG could interact with the active sites of PME, and transmission electron microscope results revealed further aggregation of PME under HHP-EGCG treatment.

18F-FDG PET-CT in Unknown-Source of Elevated Serum Carcinoembryonic Antigen (CEA) Level.

OBJECTIVE: To investigate the clinical value of 18F-FDG PET-CT in the diagnosis of malignant tumor when serum carcinoembryonic antigen (CEA) level is elevated for unknown primary lesion. STUDY DESIGN: A descriptive study. PLACE AND DURATION OF STUDY: Department of Nuclear Medicine, Luoyang Central Hospital Affiliated to Zhengzhou University, Henan, China, from March 2015 to March 2017. METHODOLOGY: A total of 120 cases of parallel 18F-FDG PET-CT examination with serum CEA level of patients with unexplained source examined were chosen. Those with a known disease or with incomplete record of clinical and/or relevant laboratory examinations were excluded. Pathological examination, results of clinical follow-up and other imaging tests constituted the clinical value of 18F-FDG PET-CT in the diagnosis of tumor. For patients who had underwent the determination of serum CEA more than twice, CEA doubling time (DT) was also calculated. The serum CEA level and CEA DT of benign versus malignant 18F-FDG PET-CT imaging results were compared. RESULTS: Thirty (25.00%) cases were finally diagnosed as malignant tumors, and 90 (75.00%) cases were excluded labelled benign condition. There was one false positive case and one false negative case each with 18F-FDG PET-CT diagnosis. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 96.7%, 98.9%, 98.3%, 96.7% and 98.9%, respectively. The serum CEA level of patients with positive 18F-FDG PET-CT imaging was higher than that of 18F-FDG PET-CT negative patients (p<0.001). The serum CEA DT of patients with positive 18F-FDG PET-CT imaging was shorter than that of 18F-FDG PET-CT negative patients (p<0.001). The receiver operating characteristic (ROC) curve analysis showed that the diagnostic efficacy of 18F-FDG PET-CT was best at serum CEA of 14.31 μg/L. CONCLUSION: 18F-FDG PET-CT imaging has high diagnostic value for patients with elevated serum CEA. For patients with serum CEA over 14.31 μg/L, the diagnostic value of 18F-FDG PET-CT for malignant tumors is more reliable.