Tsuyoshi Fukuo

Cyclic Hexamer with a Cubic Cavity: Crystal Structure of [{Rh(6-Purinethione Ribosido)(Cp*)}6](CF3SO3)6

The stereoselective formation of a pseudo-S6 hexamer resulted from the self-assembling reaction between [Rh(Cp*)(H2 O)3 ]2+ and 6-purinethione riboside (see left structure; Cp*=C5 Me5 ). The schematic representation (right) shows the direction of the coordination to the S6 and N(7) donor atoms. C (clockwise) and A (anticlockwise) indicate the chirality of each unit complex.

Determination of cyclic structure for polydithiane using electrospray ionization mass spectrometry

Disulfide polymers obtained by ring-opening polymerization have been considered to have a possibility of a cyclic catenane structure as judged from their test properties on the loss modulus and stress–strain. Electrospray ionization mass spectrometry (ESI-MS) was used to detemine molecular structure of polydithiane and polyoxyethylene to find whether they are present as a cyclic or as a linear structure. The results indicated that the polydithiane possesses the cyclic structure, and analysis of the isotope distribution of the spectral ions further showed that the polymer consists entirely of the cyclic structure without contamination of a linear polymer. A linear chain polymer with a benzylmercaptan end group was synthesized, and the ESI-MS analysis revealed that the polymer was a mixture of both the cyclic and the linear polymer. The cyclic polymer is probably formed by back-biting of the highly reactive sulfur radicals that had been formed during the polymerization reaction.

Electrospray mass analysis of chemical oxidation of 1,2-diarylcyclopropanes by Cu(II) salt

Electrospray ionization mass spectrometry was used to study chemical electron-transfer reactions of 1,2-diarylcyclopropanes by Cu(II) salt in acetonitrile. The ion [M − H]+ with a hydrogen atom loss and the solvent adduct ions, [M+42]+, etc., were detected as the initial reaction products, where [M+42]+ represents the ion whose mass is 42 u greater than the parent molecule M. From the study of deuterated derivatives, the hydrogen abstraction was revealed to occur at the 3 position of the cyclopropanes, and the mechanism of the hydrogen abstraction reaction and of the solvent addition were discussed.

Electrospray ionization mass spectrometric analysis of self-assembled 1,1′-ferrocenedicarboxylic acid

Self-assembly of 1,1′-ferrocenedicarboxylic acid in solution was detected by electrospray mass spectrometry (ESI-MS). The ESI mass spectra showed the acid was self-assembled as a cyclic tetramer in methanol and acetonitrile, and the tetramer was found to complex more strongly with the sodium ion than with any other alkali metal ion. The result was supported by semiempirical molecular orbital calculations, which indicate that the tetramer possesses a cyclic structure like a pseudo-crown ether, and its internal diameter is consistent with the diameter of a sodium ion.

MATRIX-ASSISTED LASER DESORPTION/IONIZATION AND ELECTROSPRAY IONIZATION MASS SPECTROMETRY ANALYSIS OF BLUE COPPER PROTEINS. AZURIN AND MAVICYANIN

Two copper proteins azurin-1 and azurin-2 were isolated from denitrifying bacteria Alcaligenes xylosoxidans GIFU1051, and the mass spectrometric analysis of the proteins were carried out by both matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI). The mass spectrometric analysis was also carried out with the recombinant zucchini protein mavicyanin, which was obtained by expression in Escherichia coli. All the proteins were detected as positive ions with the copper atom being eliminated. The molecular weights were determined as 14,017.6 for azurin-1, 13,807.6 for azurin-2 and 11,808.8 for mavicyanin. The observed molecular weight of azurin-1 agrees within two daltons with that calculated from the amino acid composition. Azurin-2 was found to have one different amino acid residue when compared with the known azurin-2 isolated from A. xylosoxidans NCIB11015. The measured molecular weight for the recombinant mavicyanin agrees within two daltons with that of calculated from the amino acid composition of the native protein; therefore, the recombinant mavicyanin is identical to the native protein.