JMSSJ On-line Abstracts, Vol.50, No.5 (2002)

Development of a TOF Mass Spectrometer Using a Sector Magnet and Detection of Cluster Dissociations

Satoshi TOMIE^a), Yoshihiro MANABE^b), Hiroki SAKAE^b), Takaya SATOH^b), Michisato TOYODA^b), Toshio ICHIHARA^b) ,and Itsuo KATAKUSE^*b)(^a)Development and Design of LSI for Communications Systems (3-9 Shinyokohama 2-chome,Kohoku-ku,Yokohama,Kanagawa 222-0033, Japan )
^*b)Department of Physics,Graduate School of Science,Osaka University (1-16 Machikaneyama,Toyonaka,Osaka 560-0043,Japan ))

J. Mass Spectrom. Soc. Jpn., 50(5),213-216, 2002

In 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 M_ap= M_pro²/M_pre, whereM_pro denotes the mass of product ions and M_pre; 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.

Development of an Ion Trap for an Ion Source of a Time-of-Flight Mass Spectrometer

Kousuke KUMONDAI^*a), Michisato TOYODA^a), Kenichi IWAMOTO^b), Daisuke OKUMURA^a), Morio ISHIHARA^a), Masahiro KIMURA^c), and Itsuo KATAKUSE^a) (^*a) Department of Physics, Graduate School of Science, Osaka University (1-16 Machikaneyama, Toyonaka, Osaka 560-0043, Japan)
^b) Department of Material Sciences, College of Integrated Arts and Sciences, Osaka Prefecture University (1-1 Gakuen, Sakai, Osaka 599-8531, Japan)
^c) Department of Intelligent Mechanical Systems Engineering, Kochi University of Technology(185 Miyanoguchi, Tosayamada, Kochi 782-8502, Japan))

J. Mass Spectrom. Soc. Jpn., 50(5),217-222, 2002

We 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.

Mass Spectrometric Features of S-Nitrosylated Peptides

Rina KANEKO^a) and Yoshinao WADA^*a)(^*a) Osaka Medical Center and Research Institute for Maternal and Child Health (840 Murodo-cho, Izumi, Osaka 594-1101, Japan))

J. Mass Spectrom. Soc. Jpn., 50(5),223-225, 2002

The 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.

Gas-Phase Ion / Molecule Reactions in Octafluorocyclobutane

Kiyotoshi TAKAO, Takayuki MIZUNO, Tomoyuki IINO, Fumiyuki NAKAGAWA, Hiroko SUYAMA, Kenzo HIRAOKA, and Shinichi YAMABE(Graduate School of Engineering, Yamanashi University (4-3-11 Takeda, Kofu 400-8511, Japan))

J. Mass Spectrom. Soc. Jpn., 50(5),226-228, 2002

Ion/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^-+SF_6- 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.

Theoretical Study on the Electron Capture Dissociation Correlated

Hideyuki KONISHI,^*a) Yumi YOKOTAKE,^a) and Taro ISHIBASHI^a)(^*a) Department of Chemistry, Aichi Kyoiku University (Igaya, Kariya 448-8542, Japan))

J. Mass Spectrom. Soc. Jpn., 50(5),229-232, 2002

A 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.