Takashi Fujimoto

Specific interactions between silver(I) ions and cytosine–cytosine pairs in DNA duplexes

Very specific binding of the Ag(i) ion unexpectedly stabilized DNA duplexes containing the naturally occurring cytosine-cytosine (C-C) mismatch-base pair; because the C-C pair selectively binds to the Ag(i) ion, we developed a DNA-based Ag(i) sensor that employed an oligodeoxyribonucleotide containing C-C pairs used for Ag(i) binding sites.

Crystal Structure of α,α‐Trehalose–Calcium Chloride Monohydrate Complex

The crystal structure of α,α‐trehalose hydrate complexed with calcium chloride was determined by X‐ray crystallography and its structural comparison with the α,α‐trehalose–CaBr2 · H2O complex was performed. The crystal system of the α,α‐trehalose–CaCl2 · H2O complex, C12H22O11 · CaCl2 · H2O, is orthorhombic and C2221 space group with a=10.8984(8), b=11.4260(6), and c=15.059(1)Å. Although its coordination closely resembled that of the α,α‐trehalose–CaBr2 · H2O complex published formerly assuming a pentagonal bipyramidal arrangement, a difference between two α,α‐trehalose–halide complexes was observed along the c‐axis in the infinite channels occupied by water molecules.

Characterization of the complex formation of 1,6‐anhydro‐β‐maltotriose with potassium using 1H and 39K NMR spectroscopy

The 1H and 39K longitudinal relaxation times (T1) and 1H diffusion coefficients were measured to investigate the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. Although the 1H‐T1 values of H3′, H5′, H1″ and H4″ decreased in the presence of potassium ions, 1H chemical shifts and 1H diffusion coefficients did not show significant changes. The long‐range coupling constants of 3JC−H around the glycosyl bonds did not show significant changes either. In the measurements of 39K spectra, the 39K signal obviously broadened and the 39K‐T1 values decreased in the presence of 1,6‐anhydro‐β‐maltotriose, indicating the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. These results indicate that the conformation and molecular volume were unaffected in the complex formation. Copyright

Enzymatic synthesis and the structure elucidation of novel trisaccharides comprised of D-galactose, N-acetyl-D-glucosamine, and D-fructose

GRAPHICAL ABSTRACT ABSTRACT Enzymatic synthesis of trisaccharides from N-acetylsucrosamine and lactose utilizing the transgalactosylation activity of Aspergillus oryzae β-galactosidase provided two reaction products. Structure analyses by various 2D NMR spectroscopy and MS indicated that the products were β-D-fructofuranosyl β-D-galactopyranosyl-(1→6)-2-acetamido-2-deoxy-α-D-glucopyranoside and β-D-galactopyranosyl-(1→6)-β-D-fructofuranosyl-(2↔1)-2-acetamido-2-deoxy-α-D-glucopyranoside. Moreover, J-resolved-HMBC experiments indicated that the conformations around the glycosidic bonds of these trisaccharides were very similar. Examination about the pH and thermal stabilities of the glycosidic bonds in the GlcNAc–Fru moiety of the two trisaccharides indicated apparent difference.

Binary Cationic BDDAC/Anionic DoS Surfactant Systems of Variable Compositions.Mineralization by an Advanced Oxidation Process in Aqueous Dispersions

Abstract The TiO2 photoassisted oxidation and ultimate mineralization of the cationic benzyldodecyldimethylammonium chloride (BDDAC) and the anionic sodium dodecylsulfate (DoS) surfactants in aqueous media were re-visited as part of our systematic examination of their cationic/anionic binary BDDAC/DoS complexes of variable compositions. The processes were monitored by surface tension measurements, by total organic carbon (TOC) assays, carbon dioxide evolution, and HPLC analyses. Some hydroxylated intermediates of the BDDAC system were identified by time-of-flight mass spectral (TOF-MS) techniques. Oxidative degradation of the anionic surfactant was significant involving prior adsorption of the species on the positively charged metal-oxide particle surface. By contrast, the degradation of the cationic surfactant was rather limited owing to a lesser extent of adsorption on the TiO2 surface under otherwise identical conditions. The mineralization yield assayed by CO2 evolution was ca. 80% for DoS and 47% for BDDAC after 180 min of UV irradiation. Evolution of CO2 gas for DoS was 4-fold faster (k = 1.2 × 10-2 min-1) than for BDDAC (k = 0.31 × 10-2 min-1). Mineralization of the binary mixed system was also faster (k = 0.52 × 10-2 min-1) than for the BDDAC systemalone, but 2-fold slower than for DoS alone. Initial intermediates identified by TOF-MS techniques were the mono-, di-, and tri-hydroxylated BDDAC species followed by several other intermediates with m/z greater than and less than the mass peaks of the two surfactant substrates.

Oxidation of 3-C-(2-amino-2-deoxy-D-glucopyranosyl)-1-propene compounds and the structure of 3-C-(2-amino-2-deoxy-D-glucopyranosyl)-1,2-propanediol derivatives for a synthesis of 2,3-didehydro-2,7-dideoxy-N-acetylneuraminic acid.

Oxidation of 5-acetamido-4,8-anhydro-1,2,3,5-tetradeoxy-D-glycero-D-ido-non-1-enitol [3-C-(2-amino-2-deoxy-beta-D-glucopyranosyl)-1-propene] was studied to search for preparative routes to aminodeoxy didehydro nonulosonic acid derivatives. Since only moderate chiral induction was observed with osmium tetroxide dihydroxylation as well as with peracid epoxidation, the catalytic asymmetric dihydroxylation conditions were applied to give the stereocontrolled formation of 1,2-propanediol derivatives. The structures of these diastereoisomeric 1,2-propanediol derivatives were determined by X-ray crystallographic analyses. The formation of diastereoisomeric 1,2-propanediols also varied with the nature of 2-substituent on the aminodoexy glycosyl moiety. Thus 5-acetamido-4,8-anhydro-3,5-dideoxy-D-erythro-L-ido-nonitol [(2S)-3-C-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-1,2-propanediol] was obtained predominantly up to 70% from 3-C-(2-acetamido-2-deoxyglycosyl)-1-propene by the use of ADmixbeta reagent. The (2S)-propanediol derivative was transformed in a five-step reaction sequence to 2,3-didehydro-2,7-dideoxy-N-acetylneuraminic acid.

Chemoenzymatic synthesis of sucuronic acid using d -glucurono-6,3-lactone and sucrose as raw materials, and properties of the product

Using d-glucurono-6,3-lactone (GlcL) and sucrose (Suc) as raw materials, we synthesized sucuronic acid (SucA), in which the d-glucose (Glc) residue of Suc was replaced with d-glucuronic acid, by a three-step chemoenzymatic method. In the 1st chemical step, methyl d-glucuronate (GlcAM) was synthesized by treating GlcL with a strong base anion exchange resin, Amberlite IRA402BL OH AG, in anhydrous methanol. In the 2nd step, which included an enzyme reaction, methyl sucuronate (SucAM) was synthesized from GlcAM and fructose by exploiting the transfructosylation activity of the Microbacterium saccharophilum K-1 β-fructofuranosidase, a reaction that is suppressed in the presence of high-concentration Glc. In this reaction, the addition of a Suc-non-assimilating yeast, Saccharomyces bisporus NBRC1131, to the reaction mixture increased the amount of SucAM generated, because Glc was removed from the mixture by this yeast. In the 3rd chemical step for producing sodium sucuronate (SucA·Na), SucAM was treated with Amberlite IRA402BL OH AG in water to hydrolyze SucAMs ester bond, and product was then treated with NaOH. The molar yield of SucA·Na from GlcL was 34.2%. SucA was stable at 37 °C in buffer solutions at pH 3, 5, 7, or 9. However, at temperatures exceeding 75 °C, the glycosidic bond of this disaccharide was hydrolyzed not only in acidic buffers (pH 3 and 5) but also in alkaline buffer (pH 9). SucA was not a suitable substrate for the β-fructofuranosidases of M. saccharopilum K-1 and Saccharomyces cerevisiae.