查看更多>>摘要：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 beta-protein. Also, how to detect transmembrane helix-helix and membrane protein-protein interactions and how they are modulated by lipids are discussed.
查看更多>>摘要：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.
查看更多>>摘要：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 (alpha(s1)-casein and beta-casein) extracted from baked sugar cookies were tryptic digested, the obtained phosphorylated peptides were selectively derivatized by beta-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 alpha(s1)-casein) and FQ(pSer)EEQQQTEDELQDK (33-48 fragment from beta-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 tood sample. When the present method was applied to cookies with arbitrary amounts of alpha(s1)-casein and beta-casein, the obtained quantification values were in good agreement with the arbitrary amounts spiked. The quantification limits of alpha(s1)- and beta-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.
查看更多>>摘要：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 'H 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 mu mol/L, r(2)>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.
查看更多>>摘要：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 formaz an 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 490nm. The detection limit (S/N=3) of the proposed method was 7.6nM (152 fmol/injection). The proposed method could selectively detect PQQ in food products without any clean-up procedures.
查看更多>>摘要：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 20min on an Atlantis T3 column (50 x 2.1mm i.d., 3 mu m) with a mobile phase of methanol-water. The calibration curves obtained with Eug standards showed good linearities in the range of 0.1-50 mu M (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 4.8nM, respectively. The limits of quantitation (SIN= 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 2h (>90%) at room temperature and 24h (>95%) at 4 degrees 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.
查看更多>>摘要：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 logP: -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 42min, 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 50min, and the peaks of epicatechin gallate (Erg), gallocatechin gallate (Grg), catechin gallate (Cg), propyl gallate (Pg), and resveratrol (RVT) were observed at D3 within 70min. 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 mu g/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.
查看更多>>摘要：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.
查看更多>>摘要：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 theological 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 mm(2)/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.
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