Quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide by a combination of sequential injection analysis and flow injection analysis with chemiluminescence detection

A method that combines sequential injection analysis (SIA), flow injection analysis and chemiluminescence (CL) detection was developed for the quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide (NO). The antioxidative activity was expressed as the decrease in luminol CL intensity caused by the quenching of or NO by an antioxidant. The SIA system consisted of two syringe pumps, two selection valves, two holding coils, an HPLC pump to deliver luminol solution, and a CL detector. Operation of the syringe pumps and multiport valves was controlled automatically using a personal computer with appropriate software. A hypoxanthine (HX)-xanthine oxidase (XOD) system was used for the generation of , and (±)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexenamide (NOR1) was employed as NO donor agent. The repeatability of the method was evaluated with 35.2 μg ml⁻¹ L-ascorbic acid, and the relative standard deviations (RSD) of the antioxidative activities were less than 3.8%. The quasi-simultaneous determination of the antioxidative activities in one sample was completed within 2.0 min. The antioxidative activities of some antioxidants and commercially available supplements containing certain antioxidants were successfully determined using this system. The proposed system is rapid and reproducible, and thus may be useful for the screening of functional foods, supplements and pharmaceutical formulations that exhibit antioxidative activity. Figure The system that utilizes a combination of SIA and FIA with CL for the quasi-simultaneous determination of antioxidative activity against a NO and b . SP1, 2: syringe pump, HC1, 2: holding coil, MV1, 2: multi-port valve, P: pump, D: chemiluminescence detector, I: integrator, M1, 2: mixing tee, NOR1: (±)-(E)-4-methyl-2-[(E)- hydroxyimino]-5-nitro-6-methoxy-3-hexenamide, HX: hypoxanthine, XOD: xanthine oxidase.     

Electrospray ionization-tandem mass spectrometry analysis of peptides derived by enzymatic digestion of oxidized globin subunits: An improved method to determine amino acid substitution in the hemoglobin “core”

The determination of an amino acid substitution in the “core” region of abnormal hemoglobin is technically difficult and is time- and labor-intensive both by conventional and by mass spectrometry techniques. Underivatized subunits cleaved with trypsin and lysyl endopeptidase were analyzed by high-performance liquid chromatography-electrospray ionizationmass spectrometry. The core peptides showed a series of multiply charged ions of homo- and heterodimers. Abnormal peptides in the core region could be detected in dimeric form. The sequence of core peptides was determined by product ion spectra of the peptides from oxidized globin digested with trypsin and lysyl endopeptidase. Oxidation of cysteine residues to cysteic acids in the core region resulted in the strong promotion of y-series ions by product ion analysis with a tryptic peptide from apoprotein B-100 as previously reported by Burlet, Yang, and Gaskell (J. Am. Soc. Mass Spectrom. 1992, 3, 337–344). These techniques were used to prove that substitution of an unstable hemoglobin, known as Hb Santa Ana (β88 leucine → proline), occurred in a patient with congenital hemolytic anemia. The tandem mass spectrometry analysis with oxidized globin digested with trypsin and lysyl endopeptidase offers a novel method to detect substitutions in the core region of hemoglobin.     

Current trends in isotope-coded derivatization liquid chromatographic-mass spectrometric analyses with special emphasis on their biomedical application

Currently, LC–MS has various applications in different areas such as metabolomics, pharmacokinetics, and pathological studies. Yet, matrix effects resulting from co-existing constituents remain a major problem for LC–MS [or LC–tandem mass spectrometry (LC–MS/MS)]. Moreover, technical problems and instrumental drifts may lead to ion abundance variance. Thus, an internal standard (IS) is required to guarantee the accuracy and precision of the method. Because of their limited number, isotope-coded derivatization (ICD) has been recently introduced to overcome this problem. For ICD, a stable heavy isotope-coded moiety is used for labeling the standard or the control sample and the formed products can act as ISs. A light form of the reagent is used for labeling the sample. Then, both are mixed and analyzed by LC–MS(/MS). This strategy permits the identification of different unknown analytes including potential metabolites and disease biomarkers. All these attributes lead to persistent growth in the applications of ICD LC–MS(/MS) in various biomedical branches. In this article we review the ICD methods published in the last eight years for biomedical applications as well as briefly summarize other applications for environmental and food analyses as some of their used ICD reagents were further applied for analyzing biological specimens or have the potential for that.     

Temperature dependence of thermal diffusion for aqueous solutions of monosaccharides, oligosaccharides, and polysaccharides

We studied the thermal diffusion behavior for binary aqueous solutions of glucose, maltotriose, maltohexaose, pullulan, and dextran by means of thermal diffusion forced Rayleigh scattering (TDFRS). The investigated saccharides with molar masses between 0.180 and 440 kg mol(-1) were studied in the temperature range between 15 and 55 °C. The thermal diffusion coefficient D(T) and the Soret coefficient S(T) of all solutions increase with increasing temperature. For maltohexaose and the polymers the thermal diffusion coefficient changes sign from negative to positive with increasing temperature, whereas glucose and maltotriose show only positive values in the entire investigated temperature range. While we were able to find a master curve to describe the temperature dependence of D(T), we were not able to find a similar expression for S(T). This comprehensive study allows for the first time the determination of the interaction parameters for the polymer and the solvent within the theoretical framework suggested by Würger [Phys. Rev. Lett., 2009, 102, 078302].     

Adamantyl-functionalized polymer monolith for capillary electrochromatography

An adamantyl (ADM)-functionalized monolithic stationary phase was newly synthesized by a single-step copolymerization of 1-adamantyl-(α-trifluoromethyl) acrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid in order to prevent the peak tailing of basic solutes in capillary electrochromatography and was compared with butyl methacrylate (BMA)-based one. The ADM structure shields the negatively charged groups on the surface of monolith from basic solutes, resulting in better peak shapes than BMA-based monolithic stationary phase. As the monomers ratio decreased, the monolithic column had lower retention and higher column efficiency which was likely due to lower phase ratio and smaller globule size of monolith, respectively. The ADM-functionalized monolithic columns exhibited a good repeatability and reproducibility of column preparation with relative standard deviation values below 9% in the studied chromatographic parameters.     

Emission characteristics of the dielectronic recombination line of atomic Cu and selectively excited ionic Cu line by resonance charge-transfer collision in a low-pressure laser-induced plasma.

Emisson spectra and time-resolved two-dimensional (2D) emission images of the electron-ion dielectronic recombination (i.e. a reversal process of auto-ionization) line of neutral Cu atoms, the selectively excited Cu ionic line, and normal Cu atomic line were observed for understanding the excitation mechanisms of Cu neutral and ionic lines in a low-pressure laser-induced plasma (LP-LIP) of Ar. From the observations, the number of charged particles around the emitting species seems to increase with increasing Ar pressure. Different time-resolved 2D emission images were observed among the selectively excited Cu ionic line and other Cu emission lines resulting from the different excitation mechanisms of the respective emission lines. Collisions of the second kind and electron-ion recombinations were found to be one of the major excitation mechanisms of Cu in Ar LP-LIP.     

Transformation of β-Nitro Alcohols to the Corresponding Nitro Imines with Lithium Hexamethyldisilazide (LHMDS) via Sequential Retro Nitro-Aldol–Nitro-Mannich Reaction

β-Nitro alcohols were converted to the corresponding nitro imines in the presence of lithium hexmethyldisilazide (LHMDS) in one pot. The formal transformation of the hydroxy to imino group proceeded in a sequence of the retro nitro-aldol reaction of β-nitro alcohols and the double nitro-Mannich reaction of the resulting aldimines and nitro alkane dianions.     

Determination of hydroxylated polycyclic aromatic hydrocarbons in airborne particulates by high-performance liquid chromatography with fluorescence detection.

This paper describes a highly sensitive and selective method for the determination of hydroxylated polycyclic aromatic hydrocarbons (PAHs-OH) in airborne particulates. PAHs-OH were extracted from airborne particulates with ethanol by ultrasonication. The extractant was further cleaned up by solid phase extraction (SPE) with an aminopropylsilica cartridge, and subsequently analyzed by reversed-phase high-performance liquid chromatography with fluorescence detection. 2-Hydroxy-1-acetonaphthone was used as an internal standard. By the proposed method, 2-hydroxyfluorene and 1-hydroxypyrene were identified in airborne particulates and their concentrations were determined for the first time.     

Photoresponsive self-assembly and self-organization of hydrogen-bonded supramolecular tapes

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.