Biomembranes composed of various proteins and lipids play important roles in cellular functions, such as signal transduction and substance transport. In addition, some bioactive peptides and pathogenic proteins target membrane proteins and lipids to exert their effects. Therefore, an understanding of dynamic and complex intermolecular interactions among these membrane constituents is needed to elucidate their mechanisms. This review summarizes the major research carried out in the author’s laboratory on how lipids and their inhomogeneous distributions regulate the structures and functions of antimicrobial peptides and Alzheimer’s amyloid β-protein. Also, how to detect transmembrane helix–helix and membrane protein–protein interactions and how they are modulated by lipids are discussed.

Due to the globalization of food production and distribution, the food chain has become increasingly complex, making it more difficult to evaluate unexpected food changes. Therefore, establishing sensitive, robust, and cost-effective analytical platforms to efficiently extract and analyze the food-chemicals in complex food matrices is essential, however, challenging. LC/MS-based metabolomics is the key to obtain a broad overview of human metabolism and understand novel food science. Various metabolomics approaches (e.g., targeted and/or untargeted) and sample preparation techniques in food analysis have their own advantages and limitations. Selecting an analytical platform that matches the characteristics of the analytes is important for food analysis. This review highlighted the recent trends and applications of metabolomics based on “foodomics” by LC-MS and provides the perspectives and insights into the methodology and various sample preparation techniques in food analysis.

Casein is one of the allergen proteins present in milk. Therefore, a quantification method for the selective analysis of casein using fluorous derivatization with LC-tandem mass spectrometry (LC-MS/MS) was developed. After two allergen proteins (α_S1-casein and β-casein) extracted from baked sugar cookies were tryptic digested, the obtained phosphorylated peptides were selectively derivatized by β-elimination with Ba(NO₃)₂ under basic condition and Michael addition with perfluoroalkylthiol (1H,1H,2H,2H-perfluorooctanethiol, PFOT). In this study, YKVPQLEIVPN(pSer)AQQR (104–119 fragment from α_S1-casein) and FQ(pSer)EEQQQTEDELQDK (33–48 fragment from β-casein) obtained by tryptic digestion were selected as target peptides. The phosphorylated serine residue in each peptide was converted to a perfluoroalkyl group by derivatization. The obtained fluorous-derivatized peptides were analyzed by LC-MS/MS, to which a fluorous LC column was connected. Therefore, it was possible to analyze casein without being affected by the matrix components in the baked food sample. When the present method was applied to cookies with arbitrary amounts of α_S1-casein and β-casein, the obtained quantification values were in good agreement with the arbitrary amounts spiked. The quantification limits of α_S1- and β-casein in cookie analysis were 246 and 152 ng/g, respectively. Hence, this method can be used to analyze trace amounts of allergen proteins present in the baked food.

We report on the recommendation of the simple and versatility of methylated reference (MR) to improve applications in the single reference (SR)-LC based on relative molar sensitivity (RMS). Three curcuminoids (Curs) such as curcumin, demethoxycurcumin and bisdemethoxycurcumin in turmeric products were determined using authentic standards and methylated curcumin. In addition, high-speed countercurrent chromatography (HSCCC) purification is necessary to separate Curs for indicating the RMS. For HSCCC separation, a biphasic solvent system was used to obtain these fractions, which were then subjected to ¹H quantitative NMR to determine their contents in each test solution. Using these solutions, the RMS of Curs are calculated from slopes ratios of calibration curves (three ranges from 0–100 µmol/L, r² > 0.998). The averaged RMS of Curs were 8.92 (relative standard deviation (RSD), 1.17%), 8.97 (2.18%), and 9.61 (0.77%), respectively. Cur concentrations in turmeric products can be determined using RMS, peak area, and MR content added in these samples. This proposed method, which is based on chemical methylation and the SR-LC assay has been successfully applied for the simple and reliable estimation of Curs in turmeric products.

We have developed an HPLC-UV method for the determination of pyrroloquinoline quinone (PQQ), which utilizes a redox-based colorimetric reaction. In the proposed colorimetric reaction, the redox reaction between PQQ and dithiothreitol generates superoxide anion radicals that can convert 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) to formazan dye. After PQQ separation on an octadecyl silica column, it was mixed online with dithiothreitol and INT, and the formed formazan dye was monitored by absorbance at 490 nm. The detection limit (S/N = 3) of the proposed method was 7.6 nM (152 fmol/injection). The proposed method could selectively detect PQQ in food products without any clean-up procedures.

Eugenols (Eugs) such as eugenol (Eug), methyleugenol (MeEug), and linalool (Lin) in basil product are the main bioactive components of basil products and have a terminal double-bond. A sensitive HPLC-fluorescence method for Eugs derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) was developed. Good separation of DIB-Eugs was achieved within 20 min on an Atlantis T3 column (50 × 2.1 mm i.d., 3 µm) with a mobile phase of methanol-water. The calibration curves obtained with Eug standards showed good linearities in the range of 0.1–50 µM (r ≥ 0.999). The limits of detection at a signal-to-noise ratio (S/N) = 3 for Eug, MeEug, and Lin were 1.0, 6.0, and 4.8 nM, respectively. The limits of quantitation (S/N = 10) of the Eugs were lower than 19.9 nM. The accuracies for the Eugs were within 96.8–104.6%. The intra- and inter-day precisions as relative standard deviations for the Eugs were less than 1.2 and 9.6% (n = 3). The recoveries of Eug, MeEug, and Lin were 99.0 ± 0.1, 98.0 ± 0.2, and 96.0 ± 0.4% (n = 3), respectively. The DIB-Eugs were confirmed to be stable for 2 h (>90%) at room temperature and 24 h (>95%) at 4 °C. These parameters of the proposed method were useful for the simultaneous determination of Eugs in basil products. Therefore, the developed method may be a powerful tool for the quality evaluation of dried commercially available basil products.

For the quantitative analysis of phenolic compounds in beverage samples, a three-flow channel isocratic HPLC with electrochemical detection (3LC-ECD) system was devised using a column-switching technique. Phenolic compounds with significantly different hydrophobicity (the range of calculated log P: −0.77 to 3.02) were simultaneously measured to draw three chromatograms by the 3LC-ECD; the peaks of gallic acid (GA), protocatechuic acid (PCA), and gallocatechin (GC) were observed at electrochemical detector 1 (D1) within 42 min, the peaks of procyanidin B3 (B3), epigallocatechin (EGC), catechin (C), epicatechin (EC), procyanidin B2 (B2), ethyl gallate (Eg), and epigallocatechin gallate (EGCg) were observed at D2 within 50 min, and the peaks of epicatechin gallate (ECg), gallocatechin gallate (GCg), catechin gallate (Cg), propyl gallate (Pg), and resveratrol (RVT) were observed at D3 within 70 min. The relationships between the phenolic compound concentrations and their chromatographic peak heights gave good linearity with correlation coefficients of more than 0.998. The detection limits of the phenolic compounds by the 3LC-ECD ranged from 0.6 to 3.0 µg/L. Further, the phenolic compound concentrations of commercially available teas and wines were determined with a relative standard deviation (RSD) of less than 4.9% (n = 6), and their recoveries ranged from 91 to 109%. These results indicate that the 3LC-ECD system provided an accurate, precise, and specific determination of the phenolic compounds in beverages without affecting the matrices derived from these samples.

Ferrofluids are colloidal liquids with fine magnetic particles. They change shape and fluidity depending on the magnitude and direction of the external magnetic field. The magnetic field-responsive pulsatile release of a model drug, lidocaine hydrochloride (LID·HCl), was determined using a depot-type injection containing white petrolatum and/or hydrophilic cream with a magnetic fluid in various proportions. Drug release was confirmed using a self-made diffusion cell and the application of a moving magnet at the bottom of the preparation. Magnetic field-responsive LID release was observed only when using the white petrolatum preparation and depended on the concentration of the magnetic fluid. Magnetic field responsiveness was not observed in the preparation with only the hydrophilic cream. A greater magnetic field-responsive release was observed with a combination of white petrolatum and hydrophilic cream than with white petrolatum alone. These results may lead to the development of an injectable formulation that enables pulsatile administration of macromolecular drugs.

Lecithin reverse wormlike micelles (LRWs) have been studied recently for dermal application dosage use but the effects of the physicochemical properties of oils on the formation and rheological properties of LRWs have not been investigated. We studied the effect of oil on the formation of LRWs using 5 types of liquid paraffin (LP) with kinematic viscosities ranging from 4.00 to 88.0 mm²/s. Partial phase diagrams of lecithin/water/LP systems indicated that LPs with low molecular weights could form LRWs with only a small amount of water, but LPs with high molecular weights could not form LRWs, regardless of the water concentration. The solubility of lecithin in LPs was higher for low molecular weight LPs, thus possibly affecting the formation of LRWs. The zero-shear viscosity and relaxation time of LRWs initially increased with increasing water concentration, and then decreased. The water concentration providing the maximum value was dependent on the molecular weight of the LP, whereas the maximum amount and length of the LRWs were independent of the water concentration. Our results indicate that the molecular weight of LP affects the ease of formation and the viscoelasticity of LRWs.

Osmium is defined in the international council for harmonization (ICH-Q3D) guidelines as an element whose concentration can be determined by validated methods including microwave-assisted nitric acid digestion and inductively coupled plasma mass spectrometry. However, microwave digestion using nitric acid is known to result in osmium recoveries higher than the theoretical values in spiked tests because of the formation of highly volatile osmium tetroxide in an oxidation reaction. To stabilize osmium, the addition of thiourea as a complexing agent has been tested and proved its utility. It remains unclear whether other compounds can prevent the over-recovery of osmium. In this study, we investigated four compounds, thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite, that could reduce the overestimation of osmium isotopes. The minimum amounts of thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite required to stabilize 10 ng/mL osmium in blank matrix were 1.0, 1.0, 2.5, and 2.5 g/L, respectively. The relative standard deviations obtained from 12 analyses for each stabilization solution were less than 3.3% in thiourea, 12.7% in ascorbic acid, 9.0% in sodium sulfite, and 10.6% in potassium metabisulfite. The stabilization solutions were investigated in a digested tablet matrix and were found to be effective. The impact of adding stabilization solutions on the determination of all ICH-Q3D element concentrations was also evaluated. As stabilization solutions had a small or significant impact on the determination of some elements, it was concluded that osmium determination should be conducted independently.

Despite the precise mechanisms for renal ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) are poorly understood, nuclear factor erythroid 2 related factor 2 (Nrf2) and Toll-like receptor 4 (TLR4) pathways were considered as the important targets. Leonurine (LEO) is a special alkaloid extracted from Chinese motherwort (Leonurus japonicus Houtt), which has an anti-inflammatory effect and reduces oxidative stress. We conducted the study to explore the efficacy of LEO against I/R-induced AKI in rats and further investigated the underlying mechanisms. Ischemic renal injury was induced by temporary vascular clamping for 45 min. We have measured the levels of inflammation-related biomarkers and antioxidative stress markers. Next, Western blot analysis and Real-time PCR were performed to analyze whether the Nrf2 and TLR4/nuclear factor-kappaB (NF-κB) pathways were involved in this process. We found that LEO pretreatment remarkably decreased serum creatinine and blood urea nitrogen (BUN) in I/R rats and attenuated acute tubular damage. In addition, LEO markedly increased the expression of antioxidant proteins and decreased the levels of inflammatory factors. Further study revealed that LEO promoted Nrf2 into the nucleus, promoted the expression of heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO-1), and suppressed the TLR4/NF-κB signal pathway in kidney tissues of ischemic AKI rats. The study reveals that LEO has a protective effect to prevent ischemic AKI through activation of Nrf2 nuclear translocation resisting oxidative stress injury and inhibition of the TLR4/NF-κB pathway mediated inflammatory gene expression.

Soft sensors are powerful tools for the implementation of process analytical technology (PAT). They are categorized into white-box (first-principle), black-box (statistical), and gray-box models. Gray-box models integrate white-box and black-box models to address each drawback, i.e., prediction accuracy and intuitiveness. Although they have been applied to various industrial processes, their applicability to water content monitoring in fluidized bed granulation has not been reported. In this study, we evaluated three types of gray-box models, i.e., parallel, serial, and combined gray-box models, in terms of prediction accuracy using real operating data on a commercial scale with two formulations. The gray-box models were constructed by integrating the heat and mass balance model (white-box model) and locally weighted partial least squares regression (LW-PLSR) model (black-box model). LW-PLSR was utilized to cope with collinearity and nonlinearity. In the serial gray-box models, LW-PLSR models adjusted the fitting parameters of the white-box model depending on the process parameters for each query. In the parallel gray-box or combined gray-box models, LW-PLSR models compensated for the output error of the white-box or serial gray-box models, respectively. The results demonstrated that all three types of gray-box models improved the prediction accuracy of the white-box models regardless of the formulation. Besides, we proposed the assessment method based on Hotelling’s T² and Q residual for gray-box models using LW-PLSR, which contributes decision support to select gray-box or white-box model. The accurate and descriptive gray-box models are expected to enhance process understanding and precise quality control in fluidized bed granulation.

Knoevenagel condensation, an olefin-forming reaction from active methyl/methylene-containing compounds and aldehydes, is a fundamental and useful synthetic method. Benzothiazoles are, however, out of the scope of Knoevenagel condensation. Here, we report that Knoevenagel condensation between aldehydes and 2-methyl-thiazolo[4,5-b]pyrazines (MeTPy), a fused ring structure comprising pyrazine and thiazole, proceeded smoothly, despite minor structural differences from benzothiazoles. This finding will be useful for short synthesis of MeTPy-containing functional molecules, such as a tau probe analog 1.

The electrophilic amination of nitrogen-based nucleophiles, including strong organic bases, was conducted in an Et₂O solvent using O-(mesitylenesulfonyl)hydroxylamine. Aliphatic tert-amines and N,N,N′-(trialkyl)amidines rapidly formed precipitates of the corresponding aminated salts in high yields. The amination of the highly basic and sterically hindered N,N,N′,N′,N″-(pentaalkyl)guanidines was achieved under modified conditions, although the yields were moderate because of a competing side reaction caused by the acid–base equilibrium.

Samarium diiodide (SmI₂)-mediated desymmetrization of a meso-cyclic 1,3-dione pinacol coupling is described. The reaction proceeds with high stereoselectivity to provide fused carbocyclic compounds with three contiguous stereogenic centers featuring an all-carbon quaternary center and a cis-1,2-diol moiety.