JMSSJ On-line Abstracts, Vol.48, No.1 (2000)

Mechanism of Formation of Dehydrated Ions from Abscisic Acid and Its 1',4'-Diol Methyl Esters in Electron Ionization Mass Spectrometry

Nobuhiro HIRAI,*^a) Masahiko OKAMOTO,^a) Masaki FUJIMURA,^a) Tetsuya ICHIYAMA,^a) Yasushi TODOROKI,^a) Hajime OHIGASHI,^a) Naohito TAKEDA,^b) Hideo YOSHIZUMI,^b) and the late Akira TATEMATSU^b) (*^a)Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan, ^b)Faculty of Pharmacy, Meijo University (Yagotoyama 150, Tempaku-ku, Nagoya 468-8503, Japan)

J. Mass Spectrom. Soc. Jpn., 48(1), 8-22, 2000

Hydrogen atoms lost by dehydration in electron ionization mass spectrometry of methyl esters of abscisic acid and 1',4'-trans and 1',4'-cis diolabscisic acids were identified using their deuterated analogs. Analysis of mass spectra of the deuterated analogs showed that, in methyl ester of abscisic acid, the 4-hydrogen atom bonded to a double bond was mainly eliminated with a 1'-hydroxyl group to give a dehydrated ion at m/z 260. This unusual dehydration could be due to a proximity effect between the 1'-hydroxyl group and 4-hydrogen. In methyl esters of 1',4'-diolabscisic acids, the first dehydration derived from loss of the 4'-hydroxyl group was accompanied with a hydrogen atom of the 1'-hydroxyl group, and the second dehydration derived from 1'-oxygen involved 3'-,4'-,5'-, and 7'-hydrogen atoms, and partially involved the 4-hydrogen atom. This indicated that the structure of the first dehydrated ion of the 1',4'-diolabscisic acid methyl esters was not 4'-deoxyabscisic acid methyl ester. The migration of the hydroxyl hydrogen atom to another hydroxyl group in the first dehydration has also been demonstrated in dehydration of cis-1,4-cyclohexanediol. Based on these results, we proposed dehydration mechanisms in EI MS of methyl esters of abscisic acid and 1',4'-diolabscisic acids.

Intercharge Distances in Zn₇-Metallothionein Analyzed by Nanospray on a Quadrupole Ion Trap and Molecular Modeling

Catherine FENSELAU,*^a) Zoltán SZILÁGYI,^a) and Tracie WILLIAMS^a) (^a)Department of Chemistry/Biochemistry, University of Maryland, College Park, MD 20742-2021, U.S.A.)

J. Mass Spectrom. Soc. Jpn., 48(1), 23-25, 2000

A narrow charge state distribution is observed for Zn₇-metallothionein ionized by electrospray and nano-spray ionization in solutions that conserve its native structure. Based on the structure determined by X-ray crystallography, average intercharge distances are calculated, which are consistent with earlier models for geometric distribution and with direct measurements of intercharge distances on a polypeptide.

Differentiation between N-Acetylchondrosine and N-Acetyldermosine by Matrix-Assisted Laser Desorption Ionization Time of Flight Post Source Decay Mass Spectrometry

Mamoru OHASHI,*^a) Masami ARAKI,^a) Takumi SAISU,^b) Takuji NABETANI,^b) and Haruki NIWA^b)(^*a)Department of Materials Science, Kanagawa University, Tsuchiya, Kanagawa 259-1293, Japan, ^b)Department of Applied Physics and Chemistry, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan)

J. Mass Spectrom Soc. Jpn., 48(1), 26-31, 2000

Matrix assisted laser desorption ionization (MALDI)-time of flight (TOF) post source decay (PSD) mass spectrometry has been applied to the characterization of a pair of stereoisomers, N-acetylchondrosine (1) and N-acetyldermosine (2). The stereoisomers were distinguished from each other on the basis of the PSD spectra of [M-H+2Na]⁺ as the precursor ions. A fragment ion at m/z 145 was abundant in the spectra of the latter compound, while negligible in the former. Similar behavior was observed in the cases of potassium salts of these compounds. The characteristics of MALDI-TOF-PSD spectra turned out to be quite similar to those of FAB-CID-MS/MS.

Analysis of Carotenoids by FAB CID-MS/MS

Naoshige AKIMOTO,*^a) Takashi MAOKA,^b) Yasuhiro FUJIWARA,^b) and Keiji HASHIMOTO^b) (*^a)Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-cho, Sakyou-ku, Kyoto 606-8501, Japan, ^b)Kyoto Pharmaceutical University, 5 Misasagi-nakauchi-cho, Yamashina-ku, Kyoto 607-8414, Japan)

J. Mass Spectrom. Soc. Jpn., 48(1), 32-41, 2000

Fast atom bombardment collision induced dissociation mass spectrometry/mass spectrometry (FAB CID-MS/MS) spectra were investigated to clarify the relationship between the structure and the product ions of 28 different carotenoids. In the case of β-carotene, zeaxanthin, etc. having symmetrical structure, a characteristic ion was prominently observed at [M-92]^+· generated by elimination of toluene from the polyene chain and high intensity ions corresponding 14 mass units apart (m/z 91, 105, 119) at the low mass region appeared. On the other hand, in violaxanthin, etc. having epoxy group conjugated to the polyene was observed the pronounced characteristic ion at [M-80]^+·. Product ions formed by the cleavage at the C-C bond of the polyene chain were also noticeable. Further, these spectra revealed the characteristic ions from the end group. In the case of carotenoids with the antisymmetrical structure, the fragmentation patterns were characterized by the respective end groups. On the basis of the data obtained by this FAB CID-MS/MS technique, Frit-FAB LC/MS/MS was also applied successfully to the identification of several carotenoids from paprika oleoresin.

Sensitive Analysis of Quaternary Ammonium Compound, N-Butylscopolammonium Bromide in Human Plasma and Urine by Semimicro-LC/MS

Yumiko NAKAGAWA,*^a) Tadashi SHIMAZU,^b) Yasuo ISHII,^b) Masataka ISHIBASHI,^c) and Yutaka HASHIMOTO^a) (*^a)Pharmaceuticals Group, Nippon Kayaku Co., Ltd., 3-31-12 Shimo, Kita-ku, Tokyo 115-8588, Japan, ^b)NAC Co., Ltd., 3-31-12 Shimo, Kita-ku, Tokyo 115-0042, Japan, ^c)Research & Development Dept., Takada Seiyaku Co., Ltd., 203-1 Miyamae-cho, Omiya-shi, Saitama 331-0046, Japan)

J. Mass Spectrom. Soc. Jpn., 48(1), 42-46, 2000

Sensitive analytical method of N-butylscopolammonium bromide (NBS) using LC-ESI/MS was developed and applied to determine a plasma concentration and urinary excretion of NBS. In ESI/MS intact molecular cation of NBS, quaternary ammonium salt, sensitively appeared as a base peak. NBS in plasma was effectively extracted and purified by Bond Elut C18, and determined by a semimicro-LC-ESI/MS equipped with on-line concentration system. NBS-d₉ was synthesized and used as an internal standard. Sensitivity was compared with selected ion monitoring (SIM) and selected reaction monitoring (SRM). In this case SIM was higher sensitive than SRM. The quantitation limit for this method was determined to be 4 pg per 1 mL plasma. The inter-assay precision was less than 11% (RSD). Plasma concentration of NBS in human was detectable for the first time by this method.

Effects of Solvents, Matrices, and of Reagents for Producing Adduct Ions on Liquid Ionization Mass Spectra of Monocyclic Hydrocarbon Hydroperoxides

Yoshiyuki MOCHIDA,*^a) Gorou ARAI,^a) Shigeo NAKAMURA,^a) and Masahiko TSUCHIYA^b)(*^a)Department of Applied Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1, Rokkaku-bashi, Kanagawa-ku, Yokohama 221-8686, Japan, ^b)Present address: 4-37-27 Kugayama, Suginami-ku, Tokyo 168-0082, Japan)

J. Mass Spectrom. Soc. Jpn., 48(1), 47-55, 2000

Mass spectra of hydroperoxides, such as cumen hydroperoxide (CHP), diisopropylbenzene hydroperoxide(DBH), p-mentane hydroperoxide (PMH) were investigated by liquid ionization (LPI) mass spectrometry. Hydrated molecular ions [M+H+nH₂O]⁺, n=1-10, were dominant in LPI mass spectra of all samples when they were dissolved simply in a solvent, although ethanol was a good solvent. When ethanol was used with butanol (1-3%), i.e., a mixed solvent, and/or with acetone, which was evaporated in the ionization chamber (as a vapor matrix), those hydrated ions were suppressed and [M+H]⁺ of PMH became the base peak. Acetone is a useful vapor matrix for obtaining [M+H]⁺. When pyridine (Py, 3-8%)-ethanol mixture was used as a solvent, molecular adduct ions [M+H+Py]⁺ became dominant for CHP and DBH. LPI-MS is useful not only for determining molecular weights of hydroperoxides but also for investigating the solvation and effects of various kinds of additives.

Mass Spectrometric Studies of Peptides from Cyanobacteria under FAB MS/MS Conditions

Kiyonaga FUJII,^a) Tsuyoshi MAYUMI,^a) Kazuyoshi NOGUCHI,^b) Tatsuki KASHIWAGI,^b) Satoko AKASHI,^b),** Kaarina SIVONEN,^c) Kazuo HIRAYAMA,^b) and Ken-ichi HARADA*^a) (*^a)Corresponding author: Faculty of Pharmacy, Meijo University, Tempaku, Nagoya 468-8503, Japan, Tel:81-52-832-1781 ext. 333; Fax: 81-52-834-8780; E-mail:kiharada@meijo-u.ac.jp, ^**Present address: Division of Biomolecular Characterization, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, ^a)Faculty of Pharmacy, Meijo University, Tempaku, Nagoya 468-8503, Japan, ^b)Central Research Laboratories, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki 210-8681, Japan, ^c)Department of Applied Chemistry and Microbiology, P.O. Box 56, Viikki Biocenter, FIN-00014, University of Helsinki, Finland)

J. Mass Spectrom. Soc. Jpn., 48(1), 56-64, 2000

For the elucidation of the biosynthetic relationship between nontoxic peptides and hepatotoxic peptides produced together with hepatotoxic peptides, we applied the high-energy collision FAB MS/MS method to the confirmation and the determination of the peptide structure isolated from cyanobacteria. The structures of the cyanobacterial peptides including the cyclic peptides were definitely elucidated by complementary use of the NMR and MS/MS methods. Furthermore, the MS/MS method is very effective for the structural determination of closely related peptides derived from the difference of a part of the constituent amino acids, and their structures were determined by MS/MS experiments and amino acid analysis without NMR techniques. Additionally, the charge-remote fragmentation was observed in the cases of peptides containing Arg and the sulfate group which facilitated the interpretation of the resulting product ion spectrum. From the present study, the MS/MS method was found to be practicable for the confirmation and determination of the structures of cyanobacterial peptides.

Metastable Ion Study of Organosilicon Compounds. Part XII.¹⁾ 2-Propoxytrimethylsilane, (CH₃)₃SiOCH(CH₃)₂

Osamu SEKIGUCHI,^a) Atsuyo FUJIZUKA,^a) Satoshi NAKAJIMA,^a) and Susumu TAJIMA*^a) (*^a) Chemistry and Materials Science, Gunma National College of Technology, Maebashi, Gunma 371-8530, Japan)

J. Mass Spectrom. Soc. Jpn., 48(1), 65-68, 2000

Unimolecular decomposition of 2-propoxytrimethylsilane, (CH₃)₃SiOCH(CH₃)₂ (M_w: 132, 1), upon electron impact ionization, has been studied by use of mass-analyzed ion kinetic energy (MIKE) spectrometry and D-labeling technique. The abundance of the molecular ion of 1 is too low to measure the MIKE spectrum. A methyl radical loss occurs from two different groups in 1+· ; i.e., from either trimethylsilyl group or 2-propyl group. The ion at m/z 117 formed via the latter reaction decomposes into the m/z 73 ion, trimethylsilyl ion, by the loss of acetaldehyde, whereas the ion via the former reaction decomposes exclusively into the m/z 75 ion, hydroxydimethylsilyl ion, by the loss of propene. The methyl loss from the trimethylsilyl group prevails over that from the 2-propyl one.