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Volume 50 (2002)
- Issue 6 Pages 286-
- Issue 5 Pages 213-
- Issue 4 Pages 173-
- Issue 3 Pages 100-
- Issue 2 Pages 52-
- Issue 1 Pages 1-
Volume 50, Issue 5
Displaying 1-5 of 5 articles from this issue
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REGULAR PAPERS
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Satoshi TOMIE, Yoshihiro MANABE, Hiroki SAKAE, Takaya SATOH, Michisato ...2002 Volume 50 Issue 5 Pages 213-216
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSIn the studies on dissociation patterns of clusters using a single focusing mass spectrometer, product ions decomposed between a main slit and an entrance of a magnet appear in mass spectra at mass Map= Mpro2/Mpre, whereMpro denotes the mass of product ions and Mpre; mass of precursor ions. In the case of decomposition from cluster size nto n-m(n>m), the product ions appear at size of (n-m)2/n. When n is much larger than m, (n-m)2/n is very close to (n-2m), and it is difficult to resolve the dissociated n and undissociat ed (n-2m) cluster ions. In order to study on decomposition patterns of clusters, we attached the TOF function to the sector type mass spectrometer and detected product ions. We attached the chopper in front of the main slit to get the pulsed beam and use silver clusters as the sample.View full abstractDownload PDF (258K) -
Kousuke KUMONDAI, Michisato TOYODA, Kenichi IWAMOTO, Daisuke OKUMURA, ...2002 Volume 50 Issue 5 Pages 217-222
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSWe have constructed a new apparatus which is suitable for investigating ion-molecular reactions, by combining a laboratory-made cylindrical ion trap with a time-of-flight (TOF) mass spectrometer. The cylindrical ion trap electrodes were not a mass analyzer but a reaction cell and an ion source of a mass spectrometer. The TOF mass spectrometer, developed at Osaka University, has four electric sector electrodes and can give enough mass resolution to determine reaction products with high accuracy. Several electric circuits, RF power amplifier and high voltage switch circuit, designed for ion storage and ejection are also described. As tests we have measured TOF spectra of xenon ions and iodine ions. We have observed ion-molecular reactions of iodine ions in iodine vapor. Ions created by electron ionization were stored in the ion trap up to a few seconds. While they were stored, they react with background gas. After certain storage periods, ions were ejected into the analyzing part by pulse voltage and then mass resolved. Acquired mass resolutions (m/ Δm) were about 650 and 500 for xenon and iodine, respectively. The data for iodine indicated that trimer ions I3+ comparable in amount to I2+ were produced through the reaction of I2+ ions with neutral I2 molecules.View full abstractDownload PDF (506K)
COMMUNICATIONS
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Rina KANEKO, Yoshinao WADA2002 Volume 50 Issue 5 Pages 223-225
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThe S-nitrosylation of cysteine thiols participates in the trafficking of nitric oxide (NO) in the intra- and extra-cellular milieu. To establish a mass spectrometric method to detect protein S-nitrosylation, an S-nitrosylated peptide was analyzed using different ionization modes. Electrospray ionization generated intact molecular ions, and in-source fragmentation gave rise to a loss of 30 mass units for the NO moiety. On the other hand, matrix-assisted laser desorption/ionization using an ultraviolet laser produced ions with a mass that was 29 units smaller and represented an unmodified molecule, probably due to reductive cleavage during the ionization process. All of these mass spectrometric features are diagnostic for protein S-nitrosylation.View full abstractDownload PDF (126K) -
Kiyotoshi TAKAO, Takayuki MIZUNO, Tomoyuki IINO, Fumiyuki NAKAGAWA, Hi ...2002 Volume 50 Issue 5 Pages 226-228
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSIon/molecule reactions in octafluorocyclobutane (c-C4F8) were studied using a high-pressure mass spectrometer. The thermochemical stabilities of the cluster ions of halide ions (X-) with c-C4F8 were measured. While the F- ion forms a covalent bond with c-C4F8, the interaction between other halide ions with c-C4F8 is mainly electrostatic. Theoretical calculation revealed that the halide ions interact not with the lowest unoccupied molecular orbital but with the next lowest unoccupied molecular orbital of the c-C4F8 molecule in the most stable cluster ions X- (c-C4F8). The electron affinity of c-C4F8 was measured to be 24.2±2.3 kcal/mol (1.05±0.10 eV) by observing the equilibria for reaction of SF6-+c-C4F8 = c-C4F8-+SF6- While the sound equilibrium for that reaction was established in the temperature region from ∼350 K down to the lowest temperature measured (∼150 K), that was not established in the higher temperature region above 350 K. This was attributed to the existence of an isomer for c-C4F8- whose electron detachment energy is smaller than 1.05 ev. By the measurement of thermochemical stabilitries of [(O2)m(c-C4F8)n]- (m+n = 1-3), the lower electron affinity of c-C4F8 was determined to be 12.0±1.2 kcal/mol (0.52±0.05 eV). The lower limit of the proton affinity of c-C4F8 was estimated to be 130 kcal/mol.View full abstractDownload PDF (197K) -
Hideyuki KONISHI, Yumi YOKOTAKE, Taro ISHIBASHI2002 Volume 50 Issue 5 Pages 229-232
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSA novel approach was proposed for elucidating the reaction mechanism of the electron capture dissociation (ECD) recently introduced powerful technique to characterize peptides and proteins. Against a mechanism presented so far that amide bonds catch the hydrogen atom released from the protonated peptide through electron capture, we present another mechanism focusing the proton rearrangement among the sites of the nitrogen and the oxygen atoms. This proton transfer produces various types of protonated peptides that should be responsible for the cleavage after electron capture. We carried out MO calculations on the ECD processes of glycylserine as a model peptide to elucidate how the process of proton transfer correlates with backbone cleavages. Based on the calculated energy and the molecular geometry for various stages of species concerned with the ECD process, mechanisms for proton transfer and electron capture through the Franck-Condon process were discussed. Presented here are the correlation of protonated sites to types of product ions unique in ECD and the importance of unoccupied MO's to understand the bond cleavage reactions connected with the Franck-Condon process.View full abstractDownload PDF (249K)
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