Stereoselective synthesis of amphiasterin B4: assignment of absolute configuration

The first asymmetric synthesis of (+)-amphiasterin B4 was completed from a known (S)-β-benzyloxy-γ-lactone. Comparison with the spectroscopic properties reported for authentic material has given a clear indication as to the absolute stereochemistry of the natural amphiasterin B4.     

Biradical character of linear π-conjugated oligomer dications composed of thiophene, pyrrole, and methylthio end-capping units

Combined DFT calculations and UV-vis-NIR, ESR, and SQUID measurements revealed that the ground-state electronic structure of a linear π-conjugated oligomer dication composed of two pyrrole and six or seven thiophene rings and methylthio end-capping units is dominated by a singlet biradical character.     

Preparation of Enzymatically Recyclable Hydrogels Through the Formation of Inclusion Complexes of Amylose in a Vine‐Twining Polymerization

In this paper, we describe the preparation of hydrogels through the formation of an inclusion complex of amylose in a vine‐twining polymerization. This is achieved by the phosphorylase‐catalyzed polymerization of α‐D ‐glucose 1‐phosphate from maltoheptaose primer, in the presence of a water‐soluble copolymer having hydrophobic graft‐chains (poly(acrylic acid sodium salt‐graft‐δ‐valerolactone)). The mixture turns into a gel during the polymerization process. Evaluation of the hydrogels is conducted by shear‐viscosity measurements of the products. For the hydrogels with relatively high viscosities, fast relaxation modes of the cooperative diffusions are observed by scanning microscopic light scattering measurements, which indicate the nanometer‐size network structures of the hydrogels. In addition, we found that the enzymatic disruption and reproduction of the hydrogels are achieved by the combination of the amylase‐catalyzed hydrolysis of the amylose component and the formation of amylose by the phosphorylase‐catalyzed polymerization.     

Crystallization efficiencies of inorganic polyphosphate oligomers reacted with magnesium and calcium cations using anion-exchange chromatography with particulate formation-laser scattering detector

A particulate formation-laser scattering detector (PFLSD) was developed and used for evaluating the crystallization efficiency of inorganic polyphosphates (PPs) that reacted with either magnesium or calcium cations. As the solutions for reactive crystallization, 0.5 M ammonium buffer (pH 9.6) containing either 0.15 M MgCl₂ or 0.15 M CaCl₂ (MAP: magnesium ammonium phosphate and HAP: hydroxyapatite solution) were used. In the case of mono- and diphosphate (P1 and P2), the significant dependences of the particulate formation efficiency on various types of both P1/P2 and MAP/HAP reaction solutions were observed with the direct sample injection mode. The PFLSD was hyphenated with the anion-exchange chromatography and the dependence of the particulate formation efficiency on the polymerization degree (n_p) of PP oligomers, separated chromatographically, was evaluated sequentially. The significant suppression of the particulate formation for PP oligomers was clearly confirmed, i.e., the MAP and HAP reaction solutions did not produce the particulates of the PP oligomers having an n_p value of more than 3 and 5, respectively. As the overall tendency, the particulate formation efficiency in the case of the HAP solution was superior to that in the case of the MAP solution.     

Precise and global identification of phospholipid molecular species by an Orbitrap mass spectrometer and automated search engine Lipid Search

In the present research, we have established a new lipidomics approach for the comprehensive and precise identification of molecular species in a crude lipid mixture using a LTQ Orbitrap mass spectrometer (MS) and reverse-phase liquid chromatography (RPLC) combination with our newly developed lipid search engine “Lipid Search”. LTQ Orbitrap provides high mass accuracy MS spectra by Fourier-transform (FT) mass spectrometer mode and can perform rapid MSⁿ by ion trap (IT) mass spectrometer mode. In this study, the negative ion mode was selected to detect fragment ions from phospholipids, such as fatty acid anions, by MS2 or MS3. We selected the specific detection approach by neutral loss survey-dependent MS3, for the identification of molecular species of phosphatidylcholine, sphingomyelin and phosphatidylserine. Identification of molecular species was performed by using both the high mass accuracy of the mass spectrometric data obtained from FT mode and structural data obtained from fragments in IT mode. Some alkylacyl and alkenylacyl species have the same m/z value as molecular-related ions and fragment ions, thus, direct acid hydrolysis analysis was performed to identify alkylacyl and alkenylacyl species, and then the RPLC–LTQ Orbitrap method was applied. As a result, 290 species from mouse liver and 248 species from mouse brain were identified within six different classes of phospholipid, only those in manually detected and confirmed. Most of all manually detected mass peaks were also automatically detected by “Lipid Search”. Adding to differences in molecular species in different classes of phospholipids, many characteristic differences in molecular species were detected in mouse liver and brain. More variable number of saturated and monounsaturated fatty acid-containing molecular species were detected in mouse brain than liver.     

Spectroscopy of the hyperfine structure of antiprotonic 4He and 3He

The spin magnetic moment $\mu^{\overline{p}}_{s}$ of the antiproton can be determined by comparing the measured transition frequencies in $\overline{p}^4$ He^?+? with three-body QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as $\mu^{\overline{p}}_{s} = -2.7862(83)\mu_{N}$ , slightly better than the previously best measurement. This agrees with $\mu^{p}_{s}$ within 0.24%. In 2009, a new measurement with antiprotonic ³He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on $\overline{p}^3$ He^?+?. We report here on the new experimental setup and the first tests.     

Cohomological characterization of hyperquadrics of odd dimensions in characteristic two

We consider characterizations of projective varieties in terms of their tangents. Mori established the characterization of projective spaces in arbitrary characteristic by ampleness of tangent bundles. Wahl characterized projective spaces in characteristic zero by cohomological condition of tangent bundles; in addition, he remarked that a counter-example in characteristic two is constructed from odd-dimensional hyperquadrics \(Q_{2n-1}\) with \(n > 1\) . This is caused by existence of a common point in \({\mathbb {P}}^{2n}\) which every embedded tangent space to the quadric contains. In general, a projective variety in \({{\mathbb {P}}}^N\) is said to be strange if its embedded tangent spaces admit such a common point in \({{\mathbb {P}}}^N\) . A non-linear smooth projective curve is strange if and only if it is a conic in characteristic two (Lluis, Samuel). Kleiman and Piene showed that a non-linear smooth hypersurface in \({{\mathbb {P}}}^N\) is strange if and only if it is a quadric of odd-dimension in characteristic two. In this paper, we investigate complete intersections, and prove that, a non-linear smooth complete intersection in \({{\mathbb {P}}}^N\) is strange if and only if it is a quadric in \({{\mathbb {P}}}^N\) of odd dimension in characteristic two; these conditions are also equivalent to non-vanishing of \(0\) -cohomology of \((-1)\) -twist of the tangent bundle.