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Volume 55 (2007)
- Issue 6 Pages 363-
- Issue 5 Pages 311-
- Issue 4 Pages 261-
- Issue 3 Pages 117-
- Issue 2 Pages 63-
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Volume 55, Issue 5
Displaying 1-5 of 5 articles from this issue
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INTEGRATED PAPER
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Yoko OHASHI2007 Volume 55 Issue 5 Pages 311-332
Published: 2007
Released on J-STAGE: October 15, 2007
JOURNAL FREE ACCESSThe onset of my glyco-mass spectrometry was a coincidental observation of mass spectral differences between positional isomers of phospholipids. I have been led for the last 26 years by fortunate sequences of events unfolding one after another, most times in the shape of structural determination of partially unknown samples. Struggling to rationalize fragmentation features, I have been elucidating sphingoid structures, positional isomers of sugar chains, linkage isomers of branched sugars, and finally trying to distinguish stereoisomers of sugars which is still only halfway through. With the most grateful appreciation for the award given by the Mass Spectrometry Society of Japan, my slow progress in isomer distinctions of sugars and conjugated lipids, in addition to some of the other projects I worked on along the way, are integrated in this paper.View full abstractDownload PDF (1854K)
REGULAR PAPERS
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Tatsuya YAMAMOTO, Toshifumi TAKAO, Shunsuke IZUMI, Kunihiko GEKKO2007 Volume 55 Issue 5 Pages 333-338
Published: 2007
Released on J-STAGE: October 15, 2007
JOURNAL FREE ACCESSSite-specific hydrogen/deuterium (H/D) exchange was investigated using a model protein, Escherichia coli dihydrofolate reductase, by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) coupled with two-step protease digestion by pepsin and carboxypeptidase P. Carboxypeptidase, which is generally inactive under quenching conditions (0°C and pH 2.9), produced some overlapping peptide sequences in the presence of 3.9 mM NaCl as a stabilizer. From differences in the masses of these peptides, we successfully determined the deuterium incorporation of backbone amide hydrogens of six residues—Met16 (M20 loop), Glu17 (M20 loop), Met92 (βE), Ala117 (βF-βG loop), Cys152 (βH), and Phe153 (βH)—at a higher resolution using the program Isotopica, which is capable of deconvoluting a complex isotope envelope associated with the isotope distribution of deuterated peptides. The H/D exchange kinetics data obtained were highly consistent with the local structure and fluctuation of these sites as revealed by nuclear magnetic resonance (NMR) and X-ray crystallography. These results demonstrate that MALDI MS coupled with two-step digestion is a useful tool for studying the site-specific H/D exchange of proteins without the deuterium scrambling that occurs in the gas-phase collision-induced dissociation method.View full abstractDownload PDF (921K) -
Yuichiro HASHIMOTO, Hideki HASEGAWA, Masuyuki SUGIYAMA, Hiroyuki SATAK ...2007 Volume 55 Issue 5 Pages 339-342
Published: 2007
Released on J-STAGE: October 15, 2007
JOURNAL FREE ACCESSWe performed collision-induced dissociation (CID) and electron capture dissociation (ECD) analyses using a new ion trap: an axially resonant excitation linear ion trap (AREX LIT). Unlike a conventional linear ion trap, the AREX LIT can trap and detect low m/z fragment ions, such as immonium ions and iTRAQTM reporter ions, that are produced by CID. This capability to detect low m/z fragments is realized by CID excitation in a nearly harmonic direct current potential along the linear axis. In contrast, CID excitation in a conventional linear ion trap is in a pseudo-harmonic radio frequency potential that destabilizes fragment ions whose m/z is less than 1/4 that of the precursor ions. ECD was achieved in an axial magnetic field of about 0.2 Tesla superimposed along the AREX LIT. We observed that sequential ECD/CID inside the trap improved the sequence coverage of a peptide.View full abstractDownload PDF (368K) -
Shuichi SHIMMA, Hirofumi NAGAO, Michisato TOYODA2007 Volume 55 Issue 5 Pages 343-351
Published: 2007
Released on J-STAGE: October 15, 2007
JOURNAL FREE ACCESSHigh-energy collision-induced dissociation (CID) provides characteristic structural information about interested molecules, which cannot be obtained by low energy CID. High-energy CID is available using magnetic sector or time-of-flight (TOF) type mass spectrometers. In our laboratory, a multi-turn tandem TOF mass spectrometer (MULTUM-TOF/TOF) has been developed that has a multi-turn TOF mass spectrometer (MULTUM) as the first stage and a quadratic-field ion mirror as the second stage. MULTUM-TOF/TOF enables obtaining high-energy CID spectra with high resolving power for precursor ion selection. Furthermore, the signal-to-noise (S/N) ratio of the product ion mass spectrum is dramatically improved by increasing the number of cycles, because fragment ions caused by post-source decay are eliminated. The improved S/N ratio facilitates the recognition of signal peaks that have low intensity. In this paper, we performed the structural analysis of lysophosphatidylcholine (LPC) (18 : 1) using MULTUM-TOF/TOF. We obtained ions derived not only from a dissociation of the polar headgroup but also from charge-remote fragmentation generated by a high-energy CID process. Here, charge-remote fragmentation is the cleavage of a long-chain alkyl in a fatty acid moiety. Therefore, the position of the double bonds was successfully determined. The characteristics of product ion mass spectra obtained from sodiated and protonated LPC were also investigated.View full abstractDownload PDF (2053K)
Letter from the Editor-in-Chief
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Ken-ichi YOSHINO2007 Volume 55 Issue 5 Pages 353-361
Published: 2007
Released on J-STAGE: October 15, 2007
JOURNAL FREE ACCESSSimilar to a mass spectrometer, mass spectrograph is an instrument used to obtain mass spectra. In the mass spectrograph, ions with different m/z values are passed through a magnetic sector and dispersed in different trajectories similar to the dispersion of different wavelengths of light in a prism. The ions separated according to their m/z values are directed onto the same face and are simultaneously detected by a focal plane detector. This mass spectrum-measurement system is unique for instruments called as “mass spectrographs.” However, many mass spectrometrists refer to instruments that should be called “mass spectrometers” as “mass spectrographs.”View full abstractDownload PDF (1552K)
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