Product analysis of caffeic acid oxidation by on-line electrochemistry/electrospray ionization mass spectrometry

AbstractOn-line electrochemistry/electrospray ionization mass spectrometry (EC/ESI-MS) was developed using a microflow electrolytic cell. This technique was applied to electrochemical oxidation of caffeic acid (CAF) which is known to be a highly antioxidative agent. Effects of electrolytic potentials on ion intensities of product ions and on electrolytic currents were examined at different pHs. Dimer products were detected at electrolytic potentials of E = 0.7 V (vs. Ag/AgCl) and trimer products at 1.0 V at pH 9. Dimer products were distinguished from hydrogen-bonded complexes by MS/MS experiments. Hydrogen/deuterium exchange experiments determined the number of hydroxyl and carboxyl groups in the Dimers formed by electrolysis. The mechanism of oxidative polymerization of CAF is discussed with speculation as to the structure of the dimer product

Structural Diversity Problems and the Solving Method for Antibody Light Chains

The structural diversity (heterogeneity) problem of antibodies has become a big subject along with the development of antibody drugs and catalytic antibodies. The detailed studies on the subject have not been conducted because many difficult and complex problems are existed in the phenomena. The heterogeneity problem is observed in a whole antibody as well as a catalytic antibody. The difficulty and complexity of the heterogeneity are in the generation of many isoforms caused by different charges, different molecular sizes, and/or modifications of amino acid residues. We found that the constant region domain of the antibody light chain also plays an important role in the heterogeneity. It is desirable that the antibody and/or the subunits must have a defined structure for practical use. We found interesting phenomena that copper ion can convert the multi-molecular forms of antibodies to mono-molecular forms. The ion contributed greatly to the enrichment of the dimer-form and the homogenation of the differently charged full-length and constant region domain of the light chain. The role of copper ion must be significant for preparing a single, defined, not multiple, isoform structure. Note that the big problem could be solved by using copper ion during the purification process

Electrospray mass spectrometric determination of polycyclic aromatic hydrocarbons by detecting the π-π complexes with tropylium cation

A method is presented for the determination of polycyclic aromatic hydrocarbons (PAHs) by detecting the PAH–tropylium (π donor–π acceptor) complexes using liquid chromatography-electrospray ionization-mass spectrometry.The complexes were formed by mixing with the tropylium cation after the separation of PAHs through reversed phase liquid chromatography. The detection limits,defined as three times the noise, in the selected-ion monitoring mode were 25–165 ng of the injected PAHs

Dimerization of tris (o-ureidobenzyl) amines: a novel class of aggregates

Dimeric aggregates are formed by the assembly of two tripodal moieties which are held together, both in solution and in the solid state, by a belt of 6 hydrogen-bonded urea functions

Use of thermally annealed multilayer gold nanoparticle films in combination analysis of localized surface plasmon resonance sensing and MALDI mass spectrometry

A self-assembled film of gold nanoparticles (AuNPs) with a raspberry-like morphology was prepared on a glass plate by the layer-by-layer thermal annealing of multilayer films of AuNPs. It was possible to control the morphology of the obtained films of AuNPs by changing the annealing temperature,duration of annealing, and number of layers. On investigating the plasmonic properties of these films,we found that AuNP films with a raspberry-like morphology yielded the highest refractive index unit,which is a critical parameter in localized surface plasmon resonance (LSPR) sensing, as compared to other types of AuNP films. Self-assembled AuNP films with a raspberry-like morphology were subsequently functionalized with 11-mercaptoundecanoic acid (MUA) to enable the binding of lysozyme to the MUA-modified Au surface. The superior limit of detection for the LSPR sensing of lysozyme in a buffer solution was found to be in the picomolar range (～10（12） M). The high sensitivity observed in the region was attributed to the raspberry-like morphology, where the AuNPs were packed closely together, and the electromagnetic field confinement was most intense (i.e., at hot spots). The MUA-modified, self-assembled AuNP films with a raspberry-like morphology were finally used in the combination analysis of LSPR sensing and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the selective detection and identification of lysozyme in human serum

Solvation of Lithium Irons in Mixed Organic Electrolyte Solutions by Electrospray Ionization Mass Spectroscopy

Solvation of lithium ions in mixed organic electrolyte solutions for secondary lithium batteries was investigated by electrospray ionization mass spectroscopy. The electrolyte solutions were mixed binary solutions of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene carbonate (EC),γ-butyrolactone (GBL), and propylene carbonate (PC) containing LiClO4. Lithium ions solvated mainly to two solvent molecules. The order of the inclination of the solvent molecules solvating to lithium ions is PC > EC ≒　GBL　>>　DEC > DMC

Studies on Solvation of Lithium Ions in Organic Electrolyte Solutions by Electrospray Ionization-Mass Spectroscopy

Solvation of lithium ions in organic electrolyte solutions, ethylene carbonate (EC), propylene carbonate (PC), and gamma-butyrolactone (GBL) containing LiClO4, for lithium batteries was studied by electrospray ionization-mass spectroscopy (ESI-MS). The mass spectrograms showed that a lithium ion solvated with two or three solvent molecules

Electrospray Ionization Mass Spectrometry for Mechanism Analysis of Metal Ion Complexation and Photoionization of Malachite Green Derivatives Incorporating a Crown Ether Moiety

Electrospray-ionization mass spectrometry using a photoirradiation interface has been successfully applied to the investigation of metal-ion complexation and photoionization of crowned Malachite Green leuconitrile derivatives in solution. The mass spectrometry clearly showed that the Malachite Green derivatives in their electrically neutral forms can complex metal ions with their crown ether moiety. Ionization of the Malachite Green derivatives to their corresponding cationic forms, accompanied by metal-ion repelling from their crown ether moiety, was detected upon UV-light irradiation. A remarkably different photoionization behavior in various solvents, which is difficult to detect by other analytical techniques, was also found by the mass spectrometry