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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 2
Displaying 1-5 of 5 articles from this issue
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REGULAR PAPERS
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Yoshiyuki ITOH, Yoko OHASHI, Toshimichi SHIBUE, Akio HAYASHI, Shojiro ...2002 Volume 50 Issue 2 Pages 52-57
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThree flavin-containing compounds, namely, riboflavin, riboflavin 5′-phosphate (flavin mononucleotide, FMN) and flavin-adenine dinucleotide (FAD, Scheme 1), were studied using matrix-assisted laser desorption ionization (MALDI), fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometry. It was found that the isoalloxazine ring (flavin) was reduced in the positive-ion MALDI and FAB ionization processes producing unusual ions [M+2]+· and [M+3]+ in addition to the anticipated [M+1]+, whereas ESI generated only [M+H]+ as the molecular-related ion. The reduction mechanism is hypothesized as the protonation from the matrix with a concomitant electron transfer,*1 rather than the transfer of hydrogen atom(s), H··ESI, in which matrix is not used, did not produce [M+2]+· nor [M+3]+ more than the natural isotope abundance of 13C in the sample molecules. The reduction site expands to N(1)=C(10a)-C(4a)=N(5), a1,4-diaza-1,3-butadiene system, in the isoalloxazine ring, resembling the behavior of prosthetic groups of aerobic dehydrogenases.View full abstractDownload PDF (687K) -
Masayuki KUBOTA, Keiichi YOSHIDA, Akira TAWADA, Mamoru OHASHI2002 Volume 50 Issue 2 Pages 58-66
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSPositive and negative ion electrospray ionization coupled with an ion trap mass spectrometer has been applied to the structure elucidation of three unknown species of hexaglycosides of lactosamine series obtained from keratan sulfates. Using positive and negative ion ESI-MS, the molecular weights of three unknown compounds were determined to be 1,127 (3L1P1), 1,141 (3L1P2), and 1,159 (3L1P3) corresponding to M+14, M+28, and M+46 respectively where M represents the molecular weight of the unmodified lactosamine trimer (3L1); Galβ1→4GlcNAcβ1→3Galβ1→4GlcNAcβ1→3Galβ1→4GlcNAc, M=1,113. Among them the structure elucidation of compound 3L1P1 and 3L1P3 is discussed in this paper in detail. The positive and negative (MS)4 of the disaccharide fragment ions (m/z 420 and 396, respectively) of 3L1P1 overlaps with the positive and negative (MS)2 spectra of known N-acetyllactosamine methyl glycoside (L1-OMe), respectively. On the basis of this finding the structure of 3L1P1 is concluded to be the methyl glycoside of lactosamine trimer (3L1-OMe). The disaccharide fragment ion (m/z 452) in the positive ion ESI-MS/MS spectra of compound 3L1P3 (M+46) exhibited characteristic ions, m/z 305 (m/z 452-CH(OMe)2CHNHAc-H), which suggested the presence of a dimethyl acetal structure in the reducing end sugar moiety of the hexasaccharide.View full abstractDownload PDF (1104K)
NOTE
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Satoko AKASHI, Koji TAKIO2002 Volume 50 Issue 2 Pages 67-71
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSThe structure of melittin in the presence of dioleoylphosphatidylcholine (DOPC) was investigated using hydrogen-deuterium (H/D) exchange in conjunction with collision induced dissociation (CID) in an rf-only hexapole ion guide with electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS). The deuterium incorporation into backbone amide hydrogens of melittin in the presence of DOPC was analyzed at different time points examining the mass of each fragment ion produced by hexapole-CID. The percentage of deuterium incorporation into the fragments of melittin was less than 45% at initial 10 s of isotope exchange. It increased rapidly as the exchange period was prolonged. After 300 s of incubation in D2O about 85% of amide hydrogens were exchanged with deuterium. When melittin was incubated in D2O in the presence of dodecylphosphocholine (DPC), the rate of isotope exchange was reduced at every time point. In the case of melittin alone, more than 80% amide hydrogens were exchanged with deuterium within 10 s. By comparing these time courses, it seems that the contact with DOPC did not induce melittin to change its conformation. DOPC possibly just shielded the melittin molecule while DPC induced melittin to form some stable conformation, such as helical structure. It was revealed that H/D exchange and MS analysis enabled to study such structural changes of a peptide brought about by the interaction with two types of phospholipid even in the presence of 50-fold amount of lipid.View full abstractDownload PDF (647K)
COMMUNICATIONS
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Makoto WATANABE, Tetsuya SATO, Kenzo HIRAOKA, Kunihiko MORI2002 Volume 50 Issue 2 Pages 72-74
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSSecondary ions produced by 400 eV He+ ion impact on N2 and O2 thin films deposited on a silicon substrate at 8 K were measured as a function of film thickness using a reflectron-type time-of-flight mass spectrometer. While the major ions observed were Nn+ with n up to 4 for N2 film, larger cluster ions of On+ (n up to 10) were observed. The secondary ion intensities for N2 and O2 reached the plateau with film thickness of about 20 and 400 monolayers, respectively. The observed marked difference in the film-thickness dependence between N2 and O2 films is discussed on the viewpoint of relaxation of electronic energy deposited in the solid films by the incident 400 eV He+ ions.View full abstractDownload PDF (357K) -
Keiko TADANO-ARITOMI, Toshiyuki HIKITA, Takeshi KASAMA, Sen-itiroh HAK ...2002 Volume 50 Issue 2 Pages 75-77
Published: 2002
Released on J-STAGE: October 16, 2007
JOURNAL FREE ACCESSGlyceroplasmalopsychosine, Gro1(3)-O-plasmal-O-6Galβ-sphingosine, is a unique plasmal conjugate of galactosylsphingosine (psychosine) that has an O-acetal conjugate of plasmal to the hydroxyl groups of both glycerol and galactosyl residues. Electrospray ionization ion trap mass spectrometry was applied to the structural analysis of this unique compound. In the MS/MS (MS2) spectrum produced by low energy collision-induced dissociation (CID) of the [M+H]+ ion, elimination of glycerol was predominant. MS/MS/MS (MS3) of the [M+H-glycerol]+ ion yielded an outstanding anomalous ion which required the loss of a hexose in the middle of the molecule with the plasmal residue retained on the psyhchosine side. This unexpected fragmentation by MS3 could be attributed to a rearrangement of the plasmal residue to the sphingosine residue, allowing elimination of the galactose by subsequent MS3 after CID.View full abstractDownload PDF (348K)
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