Analysis of underivatized amino acid mixtures using high performance liquid chromatography/dual oscillating nebulizer atmospheric pressure microwave induced plasma ionization-mass spectrometry

A dual oscillating capillary nebulizer (OCN) in conjunction with an atmospheric pressure microwave induced plasma ionization (AP-MIPI) source was applied to the analysis of underivatized amino acid mixtures. It was found that, compared to the single OCN, the dual OCN enhanced the sensitivity of detection several fold. Enhanced sensitivity was compound dependent. For small molecules, such as amino acids, it was 2-5 times more sensitive, while for larger molecules such as peptides it was more than an order of magnitude. The increase in sensitivity was attributed to the enhanced nebulization of the new torch. By using water/ acetonitrile containing 0.1% nonafluoropentanoic acid as the high performance liquid chromatography (HPLC) mobile phase and a C18 column, all common amino acids were separated and detected. A comparison between the results obtained using microwave induced plasma, atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) at flow rates compatible with micro LC (10-100 microL/min) showed a higher sensitivity of detection with the AP-MIPI technique for the analysis of underivatized amino acids.     

Isolation and Identification of Peptides from Soy 11S-Globulin with Hypocholesterolemic Activity

A peptide with hypocholesterolemic activity was isolated by HPLC from the pepsin hydrolysate of 11S-globulin. Its molecular weight (755.2 Da) and amino-acid sequence (Ile-Ala-Val-Pro-Gly-Glu-Val-Ala) were established. The hypocholesterolemic effect was determined by analysis of bile-acid binding and the percent inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase in vitro. The lowering of the cholesterol content is explained by bile acids bound to hydrolysate peptides shielding them from reabsorption and stimulating the transformation of cholesterol in blood plasma. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 585–588, November–December, 2005.     

Quantitative Determination of Octylonium in Human Plasma by LC–MS

The purpose of this investigation was to develop a method for measuring the concentration of octylonium in human plasma. Hydrochloric acid was added to the plasma samples before pretreatment to improve the stability of the octylonium. After liquid–liquid extraction with ethylacetate and isopropanol (10:1), the analytes were separated by chromatography on a reversed-phase C₁₈ column and detected by LC–MS–MS with electrospray ionization–ionization. The coefficient of variation for the precision of the assay was less than 10.1%, and the accuracy ranged from 98.0 to 106.5%. The limit of quantification or sensitivity was 0.2 ng mL⁻¹. This method was validated by measuring octylonium in the plasma of healthy human subjects after administration of a single 120-mg oral dose of octylonium bromide. Thus, a highly sensitive and accurate analytical method was developed to determine the concentration of octylonium in human plasma.     

Thermoluminescence detection of Korean traditional foods exposed to gamma and electron-beam irradiation

Thermoluminescence(TL) analysis was applied to detect irradiated Korean traditional condiments and soup mixes containing salt(NaCl). These food items, which are commercially irradiated in Korea, showed a consistently high correlation(R²) between the absorbed doses and the corresponding TL responses. It was proved that table salt played a role as an in-built indicator in TL measurements and its concentration in test samples was proposed as a correction factor for varying conditions of TL measurements. Pre-established threshold values were successfully adopted to identify 167 coded samples of Ramen soup mixes, both non-irradiated and irradiated with gamma and electron-beam energy. The TL intensity of irradiated soup mixes decreased with the lapse of time, but was still distinguishable from that of the non-irradiated samples at the fourth month of ambient storage. Expected estimates of absorbed doses, 2.85 and 4.75 kGv were obtained using a quadratic equation with average values of 1.57 and 4.90 kGy, respectively.     

Human beta-defensin 2 is induced by interleukin-1beta in the corneal epithelial cells

Mammalian epithelia produce the various antimicrobial peptides against the bacterial or viral infection, thereby acting as the active immune modulators in the innate immunity. In this study, we examined the effects of the various proinflammatory cytokines or LPS on cell viability and antimicrobial beta-defensin gene expressions in human corneal epithelial cells. Results showed that the cytokines or LPS did not exert severe cytotoxic effects on the cells, and that beta-defensin 1 was constitutively expressed, while beta-defensin 2 was specifically induced by IL-1beta, supporting the idea that these cytokines or LPS involve the defense mechanism in the cornea. Furthermore, the reporter and gel shift assay to define the induction mechanism of beta-defensin 2 by IL-1beta demonstrated that the most proximal NF-kappaB site on the promoter region of beta-defensin 2 was not critical for the process. Data obtained from the normal or patients with the varying ocular diseases showed that our in vitro results were relevant in the clinical settings. Our results clearly demonstrated that beta-defensin 1 and 2 are important antimicrobial peptides in the corneal tissues, and that the mechanistic induction process of beta-defensin 2 by IL-1beta is not solely dependent on proximal NF-kappaB site activation, thus suggesting that the long distal portion of the promoter is needed for the full responsiveness toward IL-1beta.     

Small angle x-ray analysis of the effect of temperature on the self-assembling columnar structures formed by a polymethacrylate with highly tapered side groups and by one of its low molar mass precursors

Small angle X-ray methods have been used to investigate the self-assembling columnar structures formed by a polymethacrylate with large highly tapered side groups, and by one of its low molar mass precursors. The polymer is poly{2-{2-[2-(2-methacryloyloxyethoxy)ethoxy] ethoxy}ethyl-3, 4, 5-tris(p-dodecyloxybenzyloxy)-benzoate} (H12-ABG-4EO-PMA); the precursor is 2-{2-[2-(2-hydroxyethoxy)-ethoxy]ethoxy}-ethyl-3, 4, 5-tris(p-dodecyl-oxybenzyloxy)benzoate (H12-ABG-4EO-OH). Both the polymer and the precursor form three dimensionally ordered structures at room temperature, consisting of hexagonally packed cylinders with diameters in the region of 60 and 53Å, respectively, in which the interiors of the columns probably have helical arrays of the stacked tapered groups. At higher temperatures these are converted to columnar hexagonal (ϕ_h) liquid crystalline phases. At temperatures close to this transition for the precursor we detect two coexisting columnar structures, with the ϕ_h structure having a diameter approximately 1Å higher than that in the solid state. For the polymer, the data are not so well resolved, and coexisting phases cannot be resolved. However, the changes in column dimensions are larger than for the precursor. Conversion of the room temperature phase to the ϕ_h phase at 40°C results in an increase of 3Å in the diameter, which then declines by approximately the same amount as the temperature rises to 90°C, close to the isotropization point. Cooling to room temperature does not immediately restore the room temperature structure. Rather, we obtain a quenched ϕ_h structure, with a column diameter almost 10% higher. These dimensional changes correlate well with the changes in diameter with temperature seen for the bulk fiber, and suggest a continuous rearrangement of the interiors of the columns in the ϕ_h phase, such as a partial unwinding of a disordered helical structure.     

Growth Properties of Carbon Nanowalls on Nickel and Titanium Interlayers

This research is conducted in order to investigate the structural and electrical characteristics of carbon nanowalls (CNWs) according to the sputtering time of interlayers. The thin films were deposited through RF magnetron sputtering with a 4-inch target (Ni and Ti) on the glass substrates, and the growth times of the deposition were 5, 10, and 30 min. Then, a microwave plasma-enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on the interlayer-coated glass substrates by using a mixture of H₂ and CH₄ gases. The FE-SEM analysis of the cross-sectional and planar images confirmed that the thickness of interlayers linearly increased according to the deposition time. Furthermore, CNWs grown on the Ni interlayer were taller and denser than those grown on the Ti interlayer. Hall measurement applied to measure sheet resistance and conductivity confirmed that the electrical efficiency improved significantly as the Ni or Ti interlayers were used. Additionally, UV-Vis spectroscopy was also used to analyze the variations in light transmittance; CNWs synthesized on Ni-coated glass have lower average transmittance than those synthesized on Ti-coated glass. Based on this experiment, it was found that the direct growth of CNW was possible on the metal layer and the CNWs synthesized on Ni interlayers showed outstanding structural and electrical characterizations than the remaining interlayer type.     

Catalytic approaches towards highly durable proton exchange membrane fuel cells with minimized Pt use

Proton exchange membrane fuel cells (PEMFCs) produce electricity from H₂ without carbon emission, and they are considered as environmentally benign energy conversion devices. Although PEMFCs are mature enough to find themselves in a few commercial automobiles such as Hyundai Nexo and Toyota Mirai, their durability should be enhanced, especially under transient conditions, and Pt use should be reduced significantly to expand their market. Herein, we introduce examples of how catalysts can contribute to enhancing the durability of PEMFCs while minimizing Pt use. Numerous electrocatalysts have been reported claiming superior activity in a half-cell setup, but they often fail to show the same enhancement in a single cell setup due to various transfer problems, impurity poisoning, etc. This perspective focuses on catalysts tested in a membrane-electrode-assembly (MEA) setup. As examples to obtain durability under transient conditions, catalysts used in reversal-tolerant anodes (RTAs) and selective anodes are explained. RTAs can endure sudden H₂ starvation, and selective anodes can operate properly when O₂ is unexpectedly mixed with H₂ in the anode. As examples with high durability in long-term operation, Pt-based nanoparticle catalysts encapsulated with carbon shells are explained. Interestingly, PtCo nanoparticles supported on Co–N–C or PtFe nanoparticles encapsulated with a carbon shell presented a superior cell performance in spite of <1/10 Pt use in an MEA setup. Non-Pt group metal (PGM) catalysts used in an MEA setup are also briefly explained. With these highly durable catalysts which can respond properly under transient conditions with minimum Pt use, PEMFC technology can bring about a more sustainable society.

Catalytic approaches to enhance PEMFC performances are introduced, especially focusing on the studies reporting MEA cell data.     

Assessment of Various Density Functional Theory Methods for Finding Accurate Structures of Actinide Complexes

Density functional theory (DFT) is a widely used computational method for predicting the physical and chemical properties of metals and organometals. As the number of electrons and orbitals in an atom increases, DFT calculations for actinide complexes become more demanding due to increased complexity. Moreover, reasonable levels of theory for calculating the structures of actinide complexes are not extensively studied. In this study, 38 calculations, based on various combinations, were performed on molecules containing two representative actinides to determine the optimal combination for predicting the geometries of actinide complexes. Among the 38 calculations, four optimal combinations were identified and compared with experimental data. The optimal combinations were applied to a more complicated and practical actinide compound, the uranyl complex (UO₂(2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene)(CH₃OH)), for further confirmation. The corresponding optimal calculation combination provides a reasonable level of theory for accurately optimizing the structure of actinide complexes using DFT.