Inner-shell excitation and ionization of linear molecules using synchrotron radiation are discussed and explained on a basis of recent outcome by several groups. Symmetry of excited states has been precisely investigated using angular distributions of produced fragment ions as well as highly energy-resolved photoabsorption spectra in consideration of theoretical prediction. It has been found that angular distributions of ion-ion coincidence signals are powerful for clarifying structural change in the inner-shell excited states of polyatomic molecules. These findings originate from fast decomposition processes following inner-shell excitation. The inner-shell hole is filled through Auger electron emission, and this emission is closely examined in these years because the Auger initial state can be clearly specified using intense monochromatic soft X-rays. Interference phenomenon between vibrational motion and core-hole lifetime has been observed in de-excitation spectra of diatomic molecules. Dissociation mechanism has been discussed using branching ratios and kinetic energies of fragment ions, and an Auger-electron fragment-ion coincidence technique is highly efficient for identifying excited molecular ion states before decomposition. A mapping technique of flight time of two fragment ions is utilized for clarifying correlation in kinetic energies and angular distributions among dissociation products in polyatomic molecules. Effect of vibrational excitation on dissociation is being studied through a progress in a brilliant and highly monochromatic soft X-ray instrument.

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We have developed the following unique methods essentially for carboxyl (C)-terminal sequencing of proteins and peptides.
The first and important observation was the successive truncation reaction of peptide with the use of 90% pentafluoropropionic acid (PFPA) and heptafluorobutyric acid (HFBA) at 90°C for 4-24 h by FAB and ESI-MS. This observation indicated two informations, one of which was the reaction-intermediate to be the prediction of the oxazolones at respective carboxyl termini of the truncated fragments, and the other was internal bond specific cleavages of carboxyl side of aspartic acid residue (Asp-C) and amino side of serine residue (Ser-N) as the side reactions.
The prediction of oxazolone promoted to use perfluorate anhydride. The extensive successive truncation was also carried out even at -20°C within 1 h by the use of the perfluorate anhydride in acetonitrile solution.
The side reactions, Asp-C and Ser-N were further studied; 0.2% PFPA aqueous vapor at 60°C for 24 h selectively cleaved Asp-Pro bond (60°C, h) and the same acid vapor at 90°C for 4-8 h cleaved Asp-C. An aqueous 90% PFPA vapor at 25°C for 48 h made N-O peptidyl shift at Ser/Thr. This was reacted with a vapor of 20% acetic anhydride and 1% acetic acid in acetoritrile at 60°C for 1 h. The reaction acetylated the free NH₂-group of the Ser/Thr and the shifted peptide fragments. And finally 20% dimethylaminoethanol (DMAE) aqueous solution at 60°C for 30 min cleaved the O-ester peptide fragment off from OH-group of Ser/Thr residue.
These two specific cleavages can be used for protein-identification by the aid of “peptide mass databases” made from protein sequence database.
The successive truncation accompanied by Asp-C or Ser-N cleavages with 90% PFPA at 90°C for 1, 2, 4, and 8 h yielded multi-C-terminal sequences of protein. The data of several residues at several sites in protein provided information for protein identification again as well as for general gene technology. In the last two methodologies TOF-MS and FAB-MS were efficiently employed.
A step wise C-terminal sequence method has been developed from the successive truncation reactions, which composed of the following three reactions; (1) formation of oxazolone and acetylation of the N-terminus with a vapor of acetic anhydride with 10% acetic acid at 60°C for 1 h; (2) cleavage off the C-terminal amino acid from the oxazolone and esterification of the peptide, and liberation of the C-terminal amino acid, with a vapor of 5% PFPA in methanol (ethanol) solution at 5°C for 5 min; and 3) hydrolysis of the peptide ester with 20% DMAE aqueous solution at 60°C for 10 min. And the products is ready to the next step reaction.

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Straight chain polydimethylsiloxanes of various molecular weight were characterized with LC/MS (liquid chromatograph/mass spectrometer) by atmospheric pressure chemical ionization (APCI) technique. The m/z 237 ion was observed as a base peak only when solvents containing methanol were used. The mass spectrum was different from those of EI and Cl and was found characteristic in the APCI technique. The structure of m/z 237 ion was considered to ion-molecule complex of CH₃⁺ and hexamethylcyclotrisiloxane. APCI mass spectra for cyclic siloxanes were measured to confirm the structure of m/z 237 ion. A detailed structure of m/z 237 ion was optimized by ab initio MO study. Diluted polydimethylsiloxane (10,000 cSt) solutions were directly introduced into APCI/MS and were detected as m/z 237 ion. The detection limit was 0.1 μg/ml. Correlation coefficient of 0.999 was obtained between concentration and intensity of m/z 237 ion.

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