Fully automated reagent peak‐free liquid chromatography fluorescence analysis of highly polar carboxylic acids using a column‐switching system and fluorous scavenging derivatization

In this study, we combined a column‐switching system with a fluorous scavenging derivatization method to develop a fully automated reagent peak‐free LC fluorescence detection protocol for the analysis of highly polar carboxylic acids. In this method, highly polar carboxylic acids were derivatized with fluorescent 1‐pyrenemethylamine in the presence of 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide and 1‐hydroxy‐1H‐benzotriazole. Residual excess of the unreacted reagent was tagged with 2‐(perfluorooctyl)ethyl isocyanate and then removed selectively using a fluorous column‐switching system placed in front of an analytical reversed‐phase column. The signal of the fluorous‐tagged unreacted reagent was completely absent in the resulting chromatograms; therefore, it did not interfere with the quantification of each acid especially those eluted before 20 min. The detection limits (S/N = 3) for the examined acids were in the range from 4.0 to 22 fmol per injection. We have applied this method to comparative analysis of highly polar carboxylic acids in urine samples obtained from diabetes mellitus type‐II model mice and their control.     

Preparation and characterization of bis(acetonitrile)bis(acetylacetonato)technetium(III)

A new chemical species of bis(acetonitrile)bis(acetylacetonato)technetium(III), [Tc(acac)₂(CH₃CN)₂]⁺, has been prepared by the reaction of tris(acetylacetonato)technetium(III) with acetonitrile in the presence of a strong acid, perchloric or hydrochloric acid. The reaction kinetics were followed by observing spectral change of Tc(acac)₃ in the UV-visible region. The complex has been characterized by combination of elemental analyses, IR and UV-visible spectrophotometry, ion-exchange chromatography, and paper electrophoresis. Applicability of this substance to synthesize mixed-ligand technetium(III) complexes was discussed based on the solubility of this complex and the ease of substitution of the acetonitrile ligand.     

Quadruple Decker [3.3][3.3][3.3]Orthocyclophane Acetal—An Orthocyclophane Ladder

Through clever bridging of orthocyclophanes (in this case by acetalization), molecules such as 1 can be formed with four benzene rings in a stacked face-to-face arrangement. UV/Vis spectroscopic and electrochemical properties of 1 are governed by π–π through-space interactions within the molecule.     

Radical Copolymerization of Vinylidene Chloride with 3(2-Methyl)-6-methylpyridazinone in Several Solvents

The radical copolymerization of vinylidene chloride (Vc, M₁) with 3(2-methyl)-6-methylpyridazinone (I, M₂) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r₁ against those of ^V C[dbnd]O and ^V C[dbnd]C of monomers determined in the solvents.     

Specific radiation and recoil energy effects in recoil implantation reaction of51Cr in metal acetylacetonates

In recoil implantation reaction of⁵¹Cr in Cr/acac/₃ a polymer component which was sensitive to radiation dose was found. However, a retention type component⁵¹Cr/acac/₃ was not so sensitive to radiation dose. A remarkable dependence of the yield of⁵¹Cr/acac/₃ on recoil energy was found in the range 10²–10⁶ eV in recoil implantation using a thin film technique. This suggests a special role of implantation reaction in solids.     

Design of New Reaction Fields for Spherical Polypyrrole Particle Synthesis

Summary: Polypyrrole conducting polymers have been investigated widely for various applications because of their thermal and environmental stability and good electrical conductivity. Using chemical oxidative polymerization for the synthesis of polypyrrole particles, the reaction rate is very fast. In this study, we designed two new reaction fields for the synthesis of spherical polypyrrole nanoparticles. In the first system, oxidative polymerization of monomer droplets infused in a water/oil (W/O) emulsion reaction field was investigated. The second system employed dispersed monomer in an aqueous solution with a low concentration of oxidant in which polymerization was augmented by ultrasonic irradiation. Effective control of the reaction rate was important for enabling the synthesis of fine spherical polypyrrole particles.     

Simple and sensitive quantification of bioactive peptides in biological matrices using liquid chromatography/selected reaction monitoring mass spectrometry coupled with trichloroacetic acid clean-up

A simple and sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method has been developed for the quantification of bioactive peptides in biological fluids. The method employs protein precipitation with 4% trichloroacetic acid (TCA) and selected reaction monitoring (SRM) using an immonium ion as the product ion. This method was applied to determine the synthetic parathyroid hormone (PTH) analog (MW 1721) in rat plasma and human hepcidin-25 (MW 2789) in human serum. TCA clean-up showed a sufficient recovery for peptides with a MW of less than 3000, and would be useful as a simple and rapid method because of direct injection of the supernatant without evaporation or dilution. In addition, TCA clean-up allowed us not only to reduce sample preparation time, but also to select an immonium ion as a product ion of SRM, which led to detection more sensitive than SRM using other types of product ions. The lower limits of quantitation (LLOQs) of the PTH analog and the human hepcidin-25 were 0.2 ng/mL and 5 ng/mL, respectively. This method was fully validated with acceptable linearity, intra- and inter-assay precisions, and accuracy. Furthermore, this simple and rapid method is applicable to pharmacokinetic studies.     

Size-selective photocatalytic reactions by titanium(IV) oxide coated with a hollow silica shell in aqueous solutions

A novel core-shell composite photocatalyst, commercially available titanium(IV) oxide (TiO(2)) particles directly incorporated into a hollow amorphous silica shell, was fabricated by successive coating of TiO(2) with a carbon layer and a silica layer followed by heat treatment to remove the carbon layer. The composite induced efficient photocatalytic reactions when relatively small substrates were used, such as methanol dehydration and decomposition of acetic acid, without any reduction in the intrinsic activity of original TiO(2), but did not exhibit efficient photocatalytic activity for decomposition of large substrates, methylene blue and polyvinyl alcohol. The unique size-selective properties of the composites are due to their structural characteristics, i.e., the presence of a pore system and a void space in the silica shell and between the shell and medial TiO(2) particles, respectively. The loading of alkylsilyl groups on the surface of the composite led to highly photostable floatability: the floated sample also induced efficient photocatalytic reaction for decomposition of acetic acid while retaining floatation at the gas/water interface.     

One-pot solid-phase glycoblotting and probing by transoximization for high-throughput glycomics and glycoproteomics

The development of rapid and efficient methods for high-throughput protein glycomics is of growing importance because the glycoform-focused reverse proteomics/genomics strategy will greatly contribute to the discovery of novel biomarkers closely related to cellular development, differentiation, growth, and aging as well as a variety of diseases such as cancers and viral infection. Recently, we communicated that rapid and efficient purification of carbohydrates can be achieved by employing sugar-specific chemical ligation with aminooxy-functionalized polymers, which we termed "glycoblotting" (see S.-I. Nishimura et al., Angew. Chem. 2005, 117, 93-98; Angew. Chem. Int. Ed. 2005, 44, 91-96). The chemoselective blotting of oligosaccharides present in crude biological materials onto synthetic polymers relies on the unique oxime-bond formation between aminooxy group displayed on the supporting materials and aldehyde/ketone group at the reducing terminal of all oligosaccharides, thus enabling highly selective and rapid oligosaccharide purification. Aiming to improve the detection sensitivity of the released oligosaccharides, we introduce here a novel strategy for one-pot solid-phase glycoblotting and probing by transoximization. We found that oligosaccharides captured by the polymer supports via the oxime bond can be released in the presence of excess O-substituted aminooxy derivatives in a weakly acidic condition. The released oligosaccharides could be recovered as newly formed oxime derivatives of the O-substituted aminooxy compound added, thus demonstrating the simultaneous releasing and probing. In addition, we synthesized a novel aminooxy-functionalized monomer, N-[2-[2-(2-tert-butoxycarbonylaminooxyacetylamino-ethoxy)ethoxy]ethyl]-2-methacrylamide, which allows for the large-scale preparation of a versatile polymer characterized by its high stability, high blotting capacity, and easy use. The one-pot protocol allowed to profile 23 kinds of N-glycan chains of human serum glycoproteins. This concept was further applied for the glycopeptides analysis in a crude mixture followed by galactose oxidase treatment to generate free aldehyde group at the non-reducing terminal of oligosaccharide moiety of glycopeptides. Our technique may be implemented in existing biochemistry and molecular diagnostics laboratories because enriched oligosaccharides and glycopeptides by solid-phase transoximization with high-sensitive labeling reagents are widely applicable in a variety of common analytical methods using two-dimensional HPLC, LC/MS, and capillary electrophoresis as well as modern mass spectrometry.     

Structure and dewetting behavior of polyhedral oligomeric silsesquioxane-filled polystyrene thin films

Polyhedral oligomeric silsesquioxane (POSS) meets increasing interest as a building unit for inorganic-organic hybrid materials. The incorporation of cyclopentyl-substituted POSS (CpPOSS) into polystyrene (PS) thin films led to an inhibition of dewetting. In this paper, the dispersion state of CpPOSS in the CpPOSS/PS hybrid films and, furthermore, the relationships between the structure and dewetting inhibition effect are discussed. Structural analysis of the hybrid films revealed that CpPOSS segregated to the film surface and crystallized. The segregation of CpPOSS to the surface changes the surface free energy and spreading coefficient of the film. Interfacial structure was also roughened by the segregation of CpPOSS, which can contribute to the inhibition of dewetting by pinning the contact line of the PS film with the substrate. The inhibition of dewetting can be attributed to the modification of the film surface and interface by the segregation of CpPOSS.