Surface chemical approach to single-step measurement of antibody in human serum using localized surface plasmon resonance biosensor on microtiter plate system

In clinical settings, serum antibody levels serve as markers of pathology. For example, antibodies related to autoimmune diseases are among the conventional targets in laboratory tests. Simple clinical tests can improve the efficacy of laboratory practice. This study describes a single-step, wash-free technique for optically detecting antibodies in human serum through the localized surface plasmon resonance (LSPR) of gold nanoparticles. As a proof-of-concept experiment, the amount of antibiotin dissolved in human serum was measured with a LSPR-based biosensor in a wash-free manner using a conventional 96-well microtiter plate and a plate reader. For an efficient surface modification of biosensors, zwitterionic copolymer was used as a scaffold on the gold nanoparticle surface to immobilize antigen and blocking reagent. Single-step, wash-free measurement of antibiotin in human serum was successfully achieved. In addition, nonspecific responses from serum contents were significantly reduced because both the copolymer and hydrophilic antigen reagent that we employed were composed of poly(ethylene oxide) spacer. Comparative experiments of the antigen-antibody reaction in serum to that in buffered solution revealed that serum is a favorable environment for the biological reaction. In conclusion, our gold-nanoparticle-based LSPR method may provide a rapid and simple way to measure the amount of antibody in serum quantitatively in clinical practice.

Rhodium phosphine-π-arene intermediates in the hydroamination of alkenes

A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine is reported. The active catalyst is shown to contain the phosphine ligand bound in a κ(1), η(6) form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C═C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes.     

Electrospray Generated from the Tip-Sealed Fine Glass Capillary Inserted with an Acupuncture Needle Electrode

In electrospray, excess charges are supplied to a sample solution by the occurrence of electrochemical reactions. Recently, different versions of electrospray, e.g., dielectric barrier electrospray ionization, inductive desorption electrospray ionization, and electrostatic-ionization driven by dielectric polarization, have been reported in which the sample solution was not in direct contact with the metal electrode but separated by dielectric materials. The objective of the current work is to elucidate the mechanism of dielectric barrier electrospray. A sealed borosilicate glass capillary inserted with a fine acupuncture needle was used as a probe. A sample solution (~ 400 nL) was captured on the glass capillary tip and a positive high voltage (HV) pulse (+?4.5 kV) was applied to the internal metal electrode. Mass spectra were measured as a function of the HV pulse width from μs to 10 s. Ions started to be detected with the pulse width of ~ 5 ms. The ion intensities increased slowly with time and reached a plateau in a few seconds. The charge distribution of cytochrome c [M?+?nH]ⁿ⁺ shifted to higher n values from a few ms to seconds. In addition to cone-jet mode normal electrospray that lasted until all the liquid sample was depleted from the glass tip, the polarization-induced electrospray ionization was observed at the early stage of the HV application.

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Synthesis of a linear-type pentanuclear (RhIII-WVI-CuI-WVI-RhIII) sulfide cluster predicted by fast atom bombardment mass spectrometry

The positive ion FAB mass spectrum of a linear trinuclear sulfide cluster, [Cp^*RhP(OEt)₃(-WS₄CuCl] (1; Cp^* = ⁵-C₅Me₅), shows many ions heavier than the molecular ion. One of the envelopes corresponds to a pentanuclear cationic cluster of [{Cp^*RhP(OEt)₃(WS₄)}₂Cu]⁺. It has been synthesized by a reaction between [Cp^*RhP(OEt)₃WS₄] and Cu⁺ in a 2:1 molar ratio as the PF₆ salt [{Cp^*RhP(OEt)₃(-WS₄)}₂Cu][PF₆] (2 · PF₆), which is characterized by a single-crystal X-ray diffraction, EXAFS, and IR measurements.This paper is dedicated to Professor Jiaxi Lu on the occassion of this 80th birthday and in recognition of his pioneering contribution to this field.     

Selective allylic hydroxylation of octahydronaphthalene derivatives with a bridgehead double bond using electrochemical method with iron picolinate complexes

The combination of electrolysis and the Fe(III)(PA)3/O2/CH3CN system was investigated for allylic hydroxylation of octahydronaphthalene derivatives. Substrates with a bridgehead double bond gave the allylic alcohol with alpha-preference, while non-bridgehead olefin did not react smoothly. This system is a useful tool for alpha-selective allylic hydroxylation of octahydronaphthalene derivatives with a bridgehead double bond as model compounds for the AB fused ring of cholesterols.     

Cyclometallation of 2-(2-thienyl)pyridine and 2-(3-thienyl)pyridine with palladium(II), rhodium(III) and ruthenium(II)

Summary 2-(2-Thienyl)pyridine [H(2-tp)] and 2-(3-thienyl)pyridine [H(3-tp)] react with lithium tetrachloropalladate(II), hexachlorotetrakis(tri-n-butylphosphine) dirhodium(III), and tetrachlorohexacarbonyldiruthenium(II) to give [PdCl(C-N)]₂-(CN=2-tp and 3-tp), [RhCl₂(C-N)PBu₃]₂ (C-N = 2-tp and 3-tp), and [RuCl(2-tp)(CO)₂]₂, respectively. Some bromo analogues are also prepared. These complexes react with pyridine and tri-n-butylphosphine to give adducts in which 2-tp is chelated through pyridine-N and thiophene-3-C and 3-tp through pyridine-N and thiophene-2-C atoms. The structures of these complexes are similar to those of the corresponding complexes of cyclometallated 2-phenylpyridine.     

Age-related changes in sensitivity to native phonotactics in Japanese infants

Japanese infants at the ages of 6, 12, and 18 months were tested on their ability to discriminate three nonsense words with different phonotactic status: canonical keetsu, noncanonical but possible keets, and noncanonical and impossible keet. The results showed that 12 and 18 months olds discriminate the keets/keetsu pair, but infants in all age groups fail to discriminate the keets/keet pair. Taken together with the findings in our previous study [Kajikawa et al., J. Acoust. Soc. Am. 120(4), 2278-2284 (2006)], these results suggest that Japanese infants develop the perceptual sensitivity for native phonotactics after 6 months of age, and that this sensitivity is limited to canonical patterns at this early developmental stage.