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Influence of boric acid on ESI ionization efficiency.

Liquid chromatography electrospray ionization mass-spectrometry (LC-ESI-MS) was used to analyze 9-fluorenylmethylmethoxycarbonyl chloride (Fmoc-Cl) and diethyl ethoxymethylenemalonate (Deemm) derivatives of three amino acids and five other compounds. Influence of boric acid on their ionization was investigated and dramatic impact on the signal was observed. Strongest signal suppression (6% of signal remains) was observed for Deemm derivative of β-Alanine (with ammonium acetate in eluent). With only formic acid as the eluent pH modifier, signal enhancement was observed, being largest for Fmoc-Cl derivative of Phenylalanine, 267%. Investigation of the influence of boric acid shows that it is a possible signal enhancer for LC-ESI-MS analysis.

Comparison of two species of Notopterygium by high- performance liquid ...

Notopterygium incisum Ting ex H.T. Chang (N. incisum) and Notopterygium forbesii Boiss (N. forbesii) are two medicinal species of Qianghuo (a well-known traditional herbal medicine in China) that are widely used in clinical prescriptions for the treatment of colds and rheumatism. To compare the chemical constituents of these two plant materials, the phenolic constituents and coumarins of these two species were comprehensively and systematically analyzed by high-performance liquid chromatography–photodiode array detection–electrospray ionization tandem mass spectrometry (HPLC/DAD/ESI-MSⁿ) for the first time. A total of 25 compounds (nine phenolic compounds and 16 coumarins) were detected in the methanol extracts. These compounds were separated on a C18 column and identified or tentatively characterized on the basis of their UV spectra and MS fragmentation behavior. In contrast to previous reports, we found that these two plant species possess very different coumarin patterns. O-Demethylfuropinnarin (18), phenethylferulate (19), notopterol (20), and isoimperatorin (22) were the predominant constituents of N. incisum, whereas nodakenin (6), 6-O-trans-feruloylnodakenin (12), p-hydroxypenethylanisate (16) and isoimperatorin (22) were the major constituents of N. forbesii. O-Demethylfuropinnarin (18), phenethylferulate (19) and notopterol (20) were only detected in N. incisum and can be regarded as useful taxonomic markers for differentiating these two plant species. Considering the marked differences in the main chemical constituents of N. incisum and N. forbesii, the biological activities of these two species should be further investigated and compared to ensure consistency and efficacy in the pharmaceutical applications of these materials.

Investigation of the copper binding site on the human islet amyloid polypeptide hormone

The metal ion binding sites of human islet amyloid polypeptide (hIAPP) have been investigated to explain the biological activity difference in the fibril formation process. The structures of [hIAPP···Cu (or Al)]ⁿ⁺ and [hIAPP_17–30···Cu]²⁺ complex were investigated by electrospray ionization–mass spectrometry (ESI–MS). The fragmentation patterns of [hIAPP···Cu (or Al)]ⁿ⁺ and [hIAPP_17–30···Cu]²⁺ complex were analyzed by tandem mass spectrometry (MS/MS) and multi-stage mass spectrometry (MS³) spectra. The [hIAPP+Cu+H]³⁺, [hIAPP+Al+H]⁴⁺ and [hIAPP_17–30+Cu]²⁺ complexes were observed in MS spectra. The Cu binding site of hIAPP is suggested to be the N₂₂–F–G–A–I₂₆ part for the [hIAPP+Cu+H]³⁺ gas-phase complex. The original hIAPP conformation was supposed to be changed by the interaction between the Cu ion and the N₂₂–F–G–A–I₂₆ part in the [hIAPP+Cu+H]³⁺ gas-phase complex.

Formation of diclofenac molecular ions as the effect of Cu2+–π ...

Solutions containing diclofenac (M) and a copper salt [CuCl₂, Cu(ClO₄)₂, Cu(NO₃)₂, CuSO₄) were analysed by electrospray ionisation mass spectrometry (ESI-MS). Because of the cation–π interactions in diclofenac–Cu(II) complexes, the diclofenac molecular ion M^+• at m/z 295 was formed. It was found that the solvent composition (methanol versus water/methanol) and counter ion strongly affect the M^+• ion formation. Formation pathways of ion M^+• are discussed.

A modified homotopy perturbation method and the axial secular frequencies of a non-linear ion trap

In this paper, a modified version of the homotopy perturbation method, which has been applied to non-linear oscillations by V. Marinca, is used for calculation of axial secular frequencies of a non-linear ion trap with hexapole and octopole superpositions. The axial equation of ion motion in a rapidly oscillating field of an ion trap can be transformed to a Duffing-like equation. With only octopole superposition the resulted non-linear equation is symmetric; however, in the presence of hexapole and octopole superpositions, it is asymmetric. This modified homotopy perturbation method is used for solving the resulting non-linear equations. As a result, the ion secular frequencies as a function of non-linear field parameters are obtained. The calculated secular frequencies are compared with the results of the homotopy perturbation method and the exact results. With only hexapole superposition, the results of this paper and the homotopy perturbation method are the same and with hexapole and octopole superpositions, the results of this paper are much more closer to the exact results compared with the results of the homotopy perturbation method.

Review: Mass spectrometry in India

This review emphasizes the mass spectrometry research being performed at academic and established research institutions in India. It consists of three main parts covering the work done in organic, atomic and biological mass spectrometry. The review reveals that the use of mass spectrometry techniques started in the middle of the 20th century and was applied to research in the fields of organic, nuclear, geographical and atomic chemistry. Later, with the advent of soft and atmospheric ionization techniques it is applied to pharmaceutical and biological research. In due course, several research centers with advanced mass spectrometry facilities have been established for specific areas of research such as gas-phase ion chemistry, ion–molecule reactions, proscribed chemicals, pesticide residues, pharmacokinetics, protein/peptide chemistry, nuclear chemistry, geochronological studies, archeology, petroleum industry, proteomics, lipidomics and metabolomics. Day- by-day the mass spectrometry centers/facilities in India have attracted young students for their doctoral research and other advanced research applications.