DIRECT MASS MEASUREMENTS OF EXOTIC NUCLEI IN STORAGE RINGS

Mass measurements of exotic nuclei is a fast, developing field which is essential for basic nuclear physics and a wide range of applications. The method of storage ring mass spectrometry has many advantages: (1) a large amount of nuclides can be simultaneously measured; (2) very short-lived (T-1/2 greater than or similar to 50 mu s) and very rare species (yields down to single ions) can be accessed; (3) nuclides in several atomic charge states can be investigated, (4) half-life measurements can be performed with time-resolved mass spectrometry. In this contribution we concentrate on some recent achievements and future perspectives of the storage ring mass spectrometry.

A high performance Time-of-Flight detector applied to isochronous mass measurement at CSRe

A high performance Time-of-Flight detector has been designed and constructed for isochronous mass spectrometry at the experimental Cooler Storage Ring (CSRe) The detector has been successfully used in an experiment to measure the masses of the N approximate to Z approximate to 33 nuclides near the proton drip-line Of particular interest is the mass of As-65 A maximum detection efficiency of 70% and a time resolution of 118 +/- 8 Ps (FWHM) have been achieved in the experiment The dependence of detection efficiency and signal average pulse height (APH) on atomic number Z has been studied The potential of APH for Z identification has been discussed (C) 2010 Elsevier B V All rights reserved

Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by ail electric field and deflected 180 degrees by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps (FWHM) was obtained in the laboratory. A mass resolution around 8 x 10(-6) For Delta m/m was achieved by using this time detector in a pilot mass measurement experiment.

High resolution mass spectrometric alveolar proteomics: Identification of surfactant protein SP-A and SP-D modifications in proteinosis and cystic fibrosis patients

In the present study, one- and two-dimensional gel electrophoresis combined with high resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) have been applied as powerful approaches for the proteome analysis of surfactant proteins SP-A and SP-D, including identification of structurally modified and truncation forms, in bronchoalveolar lavage fluid from patients with cystic fibrosis, chronic bronchitis and pulmonary alveolar proteinosis. Highly sensitive micro preparation techniques were developed for matrix-assisted laser desorption/ionization (MALDI) FT-ICR MS analysis which provided the identification of surfactant proteins at very low levels. Owing to the high resolution, FT-ICR MS was found to provide substantial advantages for the structural identification of surfactant proteins from complex biological matrices with high mass determination accuracy. Several protein bands corresponding to SP-A and SP-D were identified by MALDI-FT-ICR MS after electrophoretic separation by one- and two-dimensional gel electrophoresis, and provided the identification of structural modifications (hydroxy-proline) and degradation products.

High-sensitivity molecular mass determination of lysozyme prior to MALDI-MS

Sodium dodecyl sulfate(SDS) is a powerful solubilizing detergent which is often used during the separation of highly complex protein mixtures by one- or two-dimensional (2D) gel electrophoresis. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a widely used technique for mass spectrometric analysis of some protein molecules compared to other techniques. But the presence of SDS or some salts usually leads to signal deterioration when using MALDI-MS. A method for using nitrocellulose membrane as the solid-phase carrier combined with n-octyl-beta-D-glucopyranoside in the matrix highly enhances the sensitivity of the molecular mass determination of lysozyme. This technique has the advantage that the signal-to-noise of the molecular weight profile is improved compared with the mass spectrum and the profile is relatively easy to interpret.

Electrospray ionization tandem mass spectrometric study of the aconitines in the roots of aconite

Fragmentation pathways of aconitine-type alkaloids were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry. Low-energy collision-induced dissociation of protonated aconitines follows a dominant first step, the elimination of the C-8-substituent as acetic acid or fatty acid in MS2 spectra. Successive losses of 1-4 CH3OH molecules, 1-3 H2O, CO, benzoic acid, and CH3 or C2H5 (N-substituents) are all fragmentation pathways observed in MS3 and MS4 spectra. By applying knowledge of these fragmentation pathways to the aconitines in the ethanolic extract of aconite roots, all the known aconitines were detected and also 23 unknown aconitine-type alkaloids, in which the lipo-alkaloids containing residues of 15C, 17C and 19C saturated or unsaturated fatty acids were characterized. These odd-carbon-number fatty acid substituents have not been reported previously.

Gas-phase ion-molecule reactions of C-60 with the plasma of methyl acrylate

The gas-phase ion-molecule reactions of C-60 with the plasma generated from methyl acrylate under self-chemical ionization conditions were studied by use of a triple-quadrupole mass spectrometer. The adduct cation [C60C3H3O](+) and protonated molecular ion [C60H](+) were observed as the major product ions. The former adduct ion is formed by electrophilic reaction of C-60 with the ion [CH2=CHCO](+), a main fragment ion resulting from the methyl acrylate molecular ion [CH2=CHCOOCH3](+) through alpha cleavage. The latter ion is generated by proton transfer from protonated methyl acrylate to C-60. Semi-empirical quantum chemical calculations have been performed for the eight possible isomers of [C60C3H3O](+) at the Hartree-Fock level by use of the AMI method. The results show three types of cycloadducts as the most stable structures among the possible isomers.

Preparation and mass spectrometric study of egg yolk antibody (IgY) against rabies virus

Rabies virus was used as the antigen to immunize laying chickens. Anti-rabies virus immunoglobulin Y(IgY) was isolated from yolks of the eggs laid by these chickens using a two-step salt precipitation and one-step gel filtration protocol. The purified IgY was reduced with dithiothreitol, and heavy chains (HC) and light chains (LC) were obtained. In addition, the purified IgY was digested with pepsin and the fragment with specific antigen binding properties (Fab) was produced. Using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS), the average molecular weights of IgY, HC, LC, and Fab were determined as 167 250, 65 105, 18 660, and 45,359 Da, respectively. IgY has two structural differences compared with mammalian IgGs. First, the molecular weight of the heavy chain of IgY is larger than that of its mammalian counterpart, while the molecular weight of the light chain of IgY is smaller. Second, upon pepsin digestion, anti-rabies virus IgY is degraded into Feb, in contrast to mammalian IgG, which has been reported to be degraded into F(ab')(2) under the same conditions. Copyright (C) 2001 John Wiley & Sons, Ltd.

Electrospray ionization multiple-stage tandem mass spectrometric analysis of diglycosyldiacylglycerol glycolipids from the bacteria Bacillus pumilus

Electrospray ionization (ESI) combined with multiple-stage tandem mass spectrometry (MSn) was used to directly analyze the glycolipid mixture from bacteria Bacillus pumilus without preliminary separation. Full scan ESI-MS revealed the composition of picomole quantities of glycerolglycolipid species containing C-14-C-19 fatty acids, some of which were monounsaturated, Two main components were identified from their molecular masses and fragmentation pathways. The fragmentation pathway of the known compound compared with the investigated compound verified the proposed structure as 1(3)-acyl-2-pentadecanoyl-3(1)-O-[beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl]-sn-glycerols. A comparison of the multiple tandem mass spectra of the different alkali-metal cation adducts indicates that the intensity of fragments and the dissociation pathways are dependent on the alkali-metal type, The basic structures of glycerolglycolipids were reflected clearly from the fragmentation patterns of the sodium cations, The intense fragments of the sugar residue from the precursor ions were obtained from the lithiated adduct ions. ESI-MSn spectra of [M + K](+) ions did not provide as much fragmentation as [M + Na](+) and [M + Li](+) adducts, but their spectra allow the position of glycerol acylation to be determined. On the basis of MS2 spectra of[M + K](+) ions, it was established that all components have a C-15:0 fatty acid at the sn-2 position of the glycerol backbone and C-14-C-19 acids at the sn-1 position of the glycerol backbone. Copyright (C) 1999 John Wiley & Sons, Ltd.

Multi-stage mass spectrometric studies of triterpenoid saponins in crude extracts from Acanthopanax senticosus harms

Three triterpenoid saponins in crude extracts from Acanthopanax senticosus Harms have been investigated by use of multi-stage mass spectrometry (MSn) combined with electrospray ionization (ESI), MSn spectra were applied to direct structure elucidation of these saponins in crude plant extracts, in positive and negative ion mode. The characteristic fragmentations of triterpenoid saponins are discussed. The method provides a means of rapid initial screening of crude plant extracts. Copyright (C) 1999 John Wiley & Sons, Ltd.

X-ray photoelectron spectroscopy and mass spectra study of alpha-amino acid

X-ray photoelectron spectroscopy and mass spectrometry have been used to study the ten alpha-Amino Acids. The chemical shiftss of N-1s electron binding energy have been explained by means of the difference in the hydrocarbon group of amino acids. The influence of the hydrocarbon group on NH2 has been disscussed using the XPS and MS results.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of phospholipase A(2) and fibrinolytic enzyme, two enzymes obtained from Chinese Agkistrodon blomhoffii Ussurensis venom

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to analyze two enzymes, phospholipase AZ and fibrinolytic enzyme isolated from Chinese Agkistrodon blomhoffii Ussurensis venom. Using sinapinic acid as the matrix, positive ion mass spectra of the enzymes were obtained, In addition to the dominant protein [M+H](+) ions, multimeric and multiply charged ions were also observed in the mass spectra, The higher the concentration of the enzymes, the more multiply charged polymer and multimeric ions were detected, Our results indicate that MALDI-TOFMS can provide a rapid and accurate method for molecular weight determination of snake venom enzymes, Mass accuracies of 0.1 and 0.3 % were achieved by analysis of highly dialyzed phospholipase A2 and fibrinolytic enzyme, and these results are much better than those obtained using sodium dodecyl sulfate-palyacrylamide gel electrophoresis. MALDI-TOFMS thus provides a reliable method to determine the purity and molecular weight of these enzymes, which are of potential use as therapeutants, Copyright (C) 1999 John Wiley & Sons, Ltd.

Mass spectral study of extractable La- and Lu-containing fullerenes

Mass spectra of LaxC2n (x = 1,2), well known endohedral metallofullerenes, and Lu2C2n (2n = 76-112), new members of extractable metallofullerenes, were studied. Positive-ion laser desorption/ionization (LDI) and electron impact (EI) mass spectra indicated that lutetium is a special lanthanide that prefers to form dilutetium fullerenes by the are-burning method. However, the signals for Lu2C2n become very weak in negative-ion LDI-MS, this is different from La-2@C-80, which has close relative abundances in positive- and negative-ion MS. The distinction between Lu2C2n and La-2@C-80 in the negative-ion LDI mass spectra may be due to the different structures of La- and Lu-containing fullerenes. (C) 1997 by John Wiley & Sons, Ltd.

Mass spectrometric evidence for the generation of benzyne from benzoyl peroxide in thermolysis

Benzoyl peroxide gave rise to benzoic acid (at m/z 122) in its electron impact mass spectrum, and its perdeuterated counterpart produced perdeuterobenzoic acid, C6D5CO2D, at m/z 128 under the same conditions, An intramolecular hydrogen abstraction is proposed for the formation of benzoic acid from the peroxide in thermolysis. As a result of this reaction, benzyne would be generated simultaneously. Anthracene was employed to trap any of the reactive intermediate benzyne. Collision-induced dissociation of the ion of m/z 254 from the mixture of benzoyl peroxide and anthracene indicated that triptycene was obtained by the trapping reaction, therefore confirming that benzyne is generated from benzoyl peroxide in thermolysis.

GAS-PHASE ION-MOLECULE REACTIONS OF BUCKMINSTERFULLERENE C-60 WITH SOME SMALL ORGANIC-COMPOUNDS IN MASS-SPECTROMETER

In chemical ionization mass spectrometry (CIMS) gas phase C-60(+) or C-60 can react with fragment ions from three chloromethane and four multichloroethane molecular ions via ion-molecule reactions. A dozen of gas-phase adduct ions of C-60 are observed, and most of them contain chlorine atoms. The results of the comparison and analysis show that the relative intensities of adductions are not directly proportional to the corresponding fragment ions in the MS of reagents,which implies that some fragment ions containing radicals are more reactive with C-60(+) or C-60. This indicates that the alkene-like C-60(+) or C-60 can act as a radical sponge in addition reactions.