To elucidate the structural requirements by which EGCG analogs inhibit Aβ42 protein aggregation and remodel amyloid fibers, the molecular interactions between Aβ42 and four EGCG analogs, epigallocatechin-3-gallate (EGCG), (−)-gallocatechin gallate (GCG), (−)-epicatechin-3-gallate (ECG) and (−)-epigallocatechin (EGC), were investigated by thioflavin T fluorescence (ThT), circular dichroism (CD), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and BCA protein assay. Results revealed that the four EGCG analogs had the ability to prevent the increase of β-sheet content and inhibit Aβ42 fibrillation when added in the lag and growth phases of Aβ42 fibrillation process. When added in the equilibrium phase, the four EGCG analogs can disaggregate the preformed protofibrils/fibrils to oligomers and unfold or partially unfold oligomers. It was also observed that EGCG showed the highest inhibitory effect on Aβ42 fibrillation, followed by GCG, ECG and EGC. From the values of IC50, kinetic parameters, secondary structures, thermo-stability and solubility measurement, a reasonable conclusion can be preliminarily drawn that the structural contribution efficiency of EGCG to inhibit Aβ42 aggregation and remodel Aβ42 amyloid fibrils decreases by the order of 3′-hydroxyl group of trihydroxyphenyl ring > gallol ester moiety > stereoisomer. The findings in this work provide the structure based molecular interaction mechanism between EGCG analogs and Aβ42 amyloid protein.

A simple procedure for the determination of total phospholipids (TPL) in edible oils was developed by combining a single-step, in situ methanol/acetonitrile (MeOH/ACN) extraction of the oil sample followed by Fourier transform infrared (FTIR) spectroscopic analysis of the extract. Spectral analysis of extracts in a 25 μm CaF2 cell obtained using 1:1 MeOH/ACN added to oil in a 2:1 ratio indicated that measurements made using only the asymmetric phosphate diester PO2– stretching band at 1243 cm–1 in second-derivative spectra were sufficient for the accurate measurement of TPL with minimal coextracted triglyceride interferences being encountered. FTIR calibration spectra were devised using only phosphatidylcholine (PC) as a representative phospholipid standard, covering a range of 0–50000 μg/g TPL and spiked into 1:1 MeOH/ACN, capable of tracking the added PC with an SD of <200 μg/g. The FTIR method was initially validated using model PC-spiked degummed canola oil and subsequently with commercial crude and refined soy and rapeseed oils as well as a lecithin tablet with the FTIR TPL predictions compared to those of the AOCS Ca 12-55 molybdenate method. The FTIR method tracked the AOCS results well, being somewhat more reproducible than the reference method (±3.2 vs ±4.9%), which limited its accuracy relative to the AOCS reference procedure (±2.2%). The simple in-vial solvent extraction procedure, followed by FTIR analysis of the extract, is a simple, efficient, and rapid procedure that is also amenable to automation using an autosampler-equipped FTIR if multiple samples are to be analyzed.

•We reported biodiesel synthesis by solid-supported lipase from Burlkholderia cenocepacia via SSF.•The variables of biodiesel was optimized via Plackett–Burman and Box–Behnken designs.•Kinetics model was firstly proposed based on ethanol content with competitive inhibition.•The regression coefficients of kinetics model were determined from experiment data.•The rate-limiting reaction step from DG to MG was also illustrated.The objectives of this work were to investigate the optimization and kinetics of ethanolysis for biodiesel production by solid-supported microorganism of Burkholderia cenocepacia cultured via solid state fermentation (SSF). Operational parameters affecting the biodiesel yield were successively optimized by Plackett–Burman design followed with Box–Behnken method. The biodiesel yield of ca. 91.3% was verified under the optimized conditions of 4.3:1 of alcohol/oil molar ratio, 1.63 g/mL of solid-supported microorganism mass, 4.6% (wt/wt) of water and 44.2 °C of temperature. Furthermore, the kinetic model was developed on the basis of Ping Pong Bi Bi mechanism with competitive alcohol inhibition. The proposed model had a satisfactory correlation coefficient of R2 = 97.60%, and kinetic parameters of vmax = 3.88 mmol/(L min), KmTG=0.27mmol/L, KmC2H5OH=4.03mmol/L, and Ki = 0.34 mmol/L were obtained. In addition, the calculated activation energy (Ea) of the biocatalyst was estimated to be 37.95 kJ/mol. The rate-limiting reaction step for the ethanolysis by solid-supported microorganism in tert-butanol was demonstrated to be the conversion of di-glyceride to mono-glyceride. Finally, the reusability of the solid-supported microorganism was evaluated in successive batch reactions and presented 66.9% of original activity after 288 h repeated usage.