Elongation of the pi-system of phthalocyanines by introduction of thienyl substituents at the peripheral beta positions. Synthesis and characterization

1,4,8,11,15,18,22,25-octabutoxyphthalocyanines ((OBu)8Pcs) having eight 2-thienyl (1) and [2,2'-bithiophene]-5-yl (2) groups at beta positions and their zinc(II) and cobalt(II) derivatives were prepared from 2-thienyl- (3) or [2,2'-bithiophene]-5-yl (4)-substituted phthalonitriles in moderate to good yields. The electronic absorption spectra of the Pcs showed red-shifted Q-bands relative to beta-unsubstituted (OBu)8Pcs. The longer substituent, the [2,2'-bithiophene]-5-yl group, is more effective than the 2-thienyl group in enlarging the pi-conjugated system of the Pcs. The ring oxidation potential obtained by cyclic voltammetry shifted cathodically with increasing chain length, indicating destabilization of the HOMOs. Due to the shift of the Q-band, 2-thienyl- and [2,2'-bithiophene]-5-yl-substituted Pcs exhibit a remarkable color change from the original green color.     

Synthesis of cleonine,amino(1-hydroxycyclopropyl)acetic acid,a novel amino acid contained in cleomycin

The synthesis of cleonine, amino(1-hydroxycyclopropyl)acetic acid, a novel amino acid contained in cleomycin, a new bleomycin-phleomycin group antibiotic, is described.     

Ultrasonic Investigation of the Gelation Process of Poly(Acrylamide) Gels

The time evolution of ultrasonic velocity and attenuation has been investigated in-situ during the gelation process of polyacrylamide (PAAm) hydrogels. Longitudinal ultrasonic pulses were transmitted through the gel samples and continuously recorded to obtain the magnitude and phase of the waves as a function of time and frequency, enabling the attenuation coefficient, α, and phase velocity, v_p, of PAAm gels to be determined. The reaction was characterized by (1) an initial rapid increase in α and v_p, and (2) a subsequent reduction after both quantities passed through a peak associated with the exothermic reaction for the PAAm gelation. The square of v_p is proportional to the longitudinal modulus of the sample and inversely proportional to the density, and the values of v_p for the aged gels were smaller than those before the gelation. The cross-linker concentration dependence was further examined in order to investigate the gelation process accompanied by phase separation.     

Enantioseparation of DL-isocitric acid by a chiral ligand exchange CE with Ni(II)-D-quinic acid system

The ratio of citric acid to D ‐isocitric acid can be used to distinguish authentic and adulterated fruit juices. To separate DL ‐isocitric acid enantiomers, we used ligand exchange CE. D ‐Quinic acid was used as a chiral selector ligand and Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions were used as the central ions of the chiral selector in the BGE. DL ‐Isocitric acid was found to be enantioseparated with the above metal ions except for Mn(II) ion. The optimum running conditions for the analysis of D ‐ and L ‐isocitric acids along with citric acid, an isomer of isocitric acid, were found to be a BGE (pH 5.0) containing 30% ACN, 20 mM acetic acid, 20 mM NiSO₄, and 80 mM D ‐quinic acid. Under these conditions, DL ‐isocitric and citric acids in fruit juices were analyzed successfully.     

Palladium(II) containing γ-Keggin silicodecatungstate that efficiently catalyzes hydration of nitriles

A mixture of Pd(OAc)(2) and TBA(4)[γ-SiW(10)O(34)(H(2)O)(2)] (TBA-SiW10, TBA = [(n-C(4)H(9))(4)N](+)) showed high catalytic activities for hydration of various kinds of structurally diverse nitriles including aromatic, aliphatic, heteroaromatic, and double bond-containing ones. For hydration of 3-cyanopyridine, the turnover frequency was 860 h(-1), and the turnover number reached up to 670. A dipalladium-substituted γ-Keggin silicodecatungstate, [γ-H(2)SiW(10)O(36)Pd(2)(OAc)(2)](4-) (I), was successfully synthesized by the reaction of [γ-SiW(10)O(34)(H(2)O)(2)](4-) with Pd(OAc)(2) in a mixed solvent of acetone and water. The crystal structure of I was a monomeric, dipalladium-substituted, γ-Keggin silicodecatungstate with bidentate acetate ligands. Compound I showed similar activities and selectivities to those of a simple mixture of Pd(OAc)(2) and TBA-SiW10. The kinetic, mechanistic, and density functional theory calculation studies show that the dipalladium site plays an important role in the present hydration, and the nucleophilic attack of a hydroxide or water to the nitrile carbon atom is included in the rate-determining step.     

Dispersed platinum and tin polyaniline film electrodes for the anodes of the direct methanol fuel cell

To develop better and cheaper electrocatalysts for the oxidation of methanol in direct methanol fuel cells, several combinations of a conductive polymer polyaniline (PANI) and dispersed metal particles such as Pt and Sn were examined. The anodic current for the methanol oxidation (i _MeOH) showing the electrocatalytic activity of Pt particles was remarkably enhanced when the particles were dispersed on PANI films that should provide higher surface areas for the dispersed particles. The activity strongly depended on the morphology and the electric conductivity of the PANI films electropolymerized in five different acid solutions: H₂SO₄, HNO₃, HClO₄, HBF₄, and HCl. The highest activity was achieved using the dispersed Pt particle on PANI film electropolymerized from H₂SO₄ polymerizing solution. In order to reduce the dispersed amount of the expensive Pt particles, other metal particles were pre-dispersed on the PANI film prepared from the H₂SO₄ polymerizing solution, and then Pt particles were dispersed on the film. Among the pre-dispersed metal particles attempted here (Sn, Cu, Cr, Ni, In, Co, Sb, Bi, Pb, and Mn), the highest activity was obtained with Sn particles. When the ratio of dispersed Pt to Sn particles ranges from 32:68 to 100:0, i _MeOH is higher than that measured with the dispersed Pt particle on PANI films without the Sn particles. This means that the dispersed amount of the Pt particles could be reduced by utilizing dispersed Sn particles.     

A general strategy to determine a target DNA sequence of a short peptide: application to a d-peptide.

Short peptides could potentially provide a novel element to read-out DNA sequences from the major groove. However, it is difficult to determine sequence-preference of de novo designed monomeric short peptides. Because DNS-binding affinity and specificity of short peptides are usually much lower than those of native DNA-binding proteins, determining the sequence-preference of short peptides by conventional methods utilized to deduce the target sequence of proteins often produces an unclear outcome. We report here a general strategy to defining the sequence-preference of a DNA-binding short peptide by using the heterodimers. A GCN4 basic region peptide tethers a low-affinity DNA-binding peptide adjacent to a GCN4 binding sequence through the cyclodextrin-adamantane association, thereby increasing local concentration of the low-affinity peptide on degenerated DNA sequences. An increase of the local concentration allows one to select a preferential sequence for the low-affinity DNA binding peptide. The method successfully identified specific sequences of short peptides derived from native DNA-binding proteins. The usefulness of this approach has been demonstrated by identifying preferred DNA targets for a peptide composed only of d-amino acids. The method is potentially applicable not only to artificial peptides, but also to other synthethic ligands.     

Room-Temperature Alkyl-Diphenylpyrene Liquefication by Molecular Desymmetrization

Achieving the lowest phase transition temperature with minimal chemical modification in highly crystalline π-conjugated molecules is a universal problem in related research fields. This paper reports room-temperature liquefication of diphenylpyrene isomers by introducing bulky yet flexible branched alkyl chains through molecular desymmetrization. Six isomers with different symmetries depending on the positions of the phenyl groups and alkyl groups were synthesized, and three of the isomers were found to be liquids at 25 °C, a state in which they have remained for more than five years. Although it is generally believed that the lower the symmetry of a molecule, the less likely it is to crystallize, one molecule with a relatively high molecular symmetry unexpectedly did not crystallize, which was evidenced by the kinetic inhomogeneity of this amorphous material (practically stable liquid) assessed by rheological analysis.     

Frequency measurement of pure rotational transitions of OD

Frequencies of pure rotational transitions of OD⁻ have been measured in the 1-5 THz region using a high-precision tunable far-infrared spectrometer based on difference frequency of two CO₂ lasers. The measured frequencies were analyzed together with the data in the infrared and the sub-millimeter region to refine the rotational parameters. Isotopically invariant Dunham parameters were also obtained.     

Target-specific chemical acylation of lectins by ligand-tethered DMAP catalysts

Because sugar-binding proteins, so-called lectins, play important roles in many biological phenomena, the lectin-selective labeling should be useful for investigating biological processes involving lectins as well as providing molecular tools for analysis of saccharides and these derivatives. We describe herein a new strategy for lectin-selective labeling based on an acyl transfer reaction directed by ligand-tethered DMAP (4-dimethylaminopyridine). DMAP is an effective acyl transfer catalyst, which can activate an acyl ester for its transfer to a nucleophilic residue. To direct the acyl transfer reaction to a lectin of interest, we attached the DMAP to a saccharide ligand specific for the target lectin. It was clearly demonstrated by biochemical analyses that the target-selective labeling of Congerin II, an animal lectin having selective affinity for Lactose/LacNAc (N-acetyllactosamine), was achieved in the presence of Lac-tethered DMAPs and acyl donors containing probes such as fluorescent molecules or biotin. Conventional peptide mapping experiments using HPLC and tandem mass-mass analysis revealed that the acyl transfer reaction site-specifically occurred at Tyr 51 of Cong II. This strategy was successfully extended to other lectins by changing the ligand part of the ligand-tethered DMAP. We also demonstrated that this labeling method is applicable not only to purified lectin in test tubes, but also to crude mixtures such as E. coli lysates or homogenized animal tissue samples expressing Congerin.