Accelerated glycosylation under frozen conditions

O-Glycosylations using thiomethyl glycosides as donors were compared under both frozen and unfrozen conditions. In the presence of MeOTf as a promoter, enormous rate acceleration was observed when the glycosylation was conducted in p-xylene below its freezing point.     

Speciation of mercury in salmon egg cell cytoplasm in relation with metallomics research

Speciation of mercury in salmon egg cell cytoplasm was investigated by surfactant-mediated high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICP-MS), where an ODS (octadecylsilica) column coated with a bile acid derivative, CHAPS (3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate), was used for species separation. Prior to the speciation analysis, total Hg in the cell cytoplasm was determined by ICP-MS at m/z 202 in a flow injection mode. For the precise measurement, salmon egg cell cytoplasm was diluted five-fold with 0.1 M Tris (Tris(hydroxymethyl)aminomethane)-HNO₃ buffer solution, and the standard addition method was employed. Thus, the total concentration of Hg in cell cytoplasm was estimated to be 12.4 ng g⁻¹ on the wet weight basis. Next, the cell cytoplasm diluted five-fold with 0.1 M Tris-HNO₃ buffer solution was analyzed by surfactant-mediated HPLC with the dual detection system of a UV absorption detector and an ICP-MS instrument. Two peaks corresponding to some proteins and small molecules were mainly observed in those chromatograms. When salmon egg cell cytoplasm was diluted five-fold with 0.01 M Tris buffer solution or pure water, some precipitates appeared probably because of precipitation of hydrophobic proteins in cytoplasm. After the precipitates were eliminated with a membrane filter, the filtrate was subjected to the analysis by surfactant-mediated HPLC/UV/ICP-MS. As a result, the peaks for small molecular species of Hg were clearly observed at the retention time near 4.0 min (corresponding to low-molecular weight zone) in the chromatograms with UV absorption detection as well as with Hg- and S-specific ICP-MS detections. The small molecule bound with Hg was identified as cysteine through the cysteine-spiked experiment. In addition, the protein fraction on the chromatogram obtained by using the CHAPS-coated ODS column was further analyzed by SEC (size exclusion chromatography). Consequently, several protein peaks with molecular weight of 300, 50 and 12 kDa were observed in all the detections of UV absorption, Hg and Se, although two peaks among them were coincident in the case of S. These results indicate that Hg in salmon egg cell cytoplasm binds with proteins containing selenocysteine and/or cysteine residues in proteins.     

Assessing the performance of density functional theory for the electronic structure of metal-salens: the M06 suite of functionals and the d⁴-metals

We have systematically investigated the electronic structure of the d? metal-salen complexes including the Cr(II)-, Mn(III)-, Fe(IV)-, Mo(II)-, Tc(III)-, and Ru(IV)-salen complexes. Density functional theory (DFT) has been employed, using the BP86 and B3LYP functionals, and the entire M05 and M06 suites of meta-generalized gradient functionals. These results are compared to robust complete active-space self-consistent field (CASSCF) optimized geometries and complete active-space third-order perturbation theory (CASPT3) energies for the lowest singlet, triplet, and quintet states. Although the M06 and M06-L DFT functionals have been generally recommended for computations on complexes that contain main group and transition metals, none of the M0-functionals appear statistically better than the B3LYP functional for the computation of spin-state energy gaps. DFT- and CASSCF-optimized geometries normally agree to within 0.3 ? least root mean squared deviation (LRMSD) for the singlet and triplet structures and less than 0.1 ? LRMSD for the quintet structures. It can be concluded that no DFT functional tested here can be considered reliable over all metal-salen complexes and it is highly recommended that the accuracy of any given DFT functional should be assessed on a case-by-case basis.     

Stellatolide H,a cytotoxic peptide lactone from a deep-sea sponge Discodermia sp.

Stellatolide H (1) was isolated from a deep-sea sponge Discodermia sp. as the cytotoxic constituent. The planar structure of 1 was elucidated on the basis of the NMR spectroscopic and mass spectrometric data. The absolute configurations of the constituent amino acid residues were determined by the Marfey’s method. Stellatolide H (1) is a peptide lactone of the callipeltin class with its N-terminus blocked by 3-hydroxy-6,8-dimethyldeca-(4Z,6E)-dienoic acid (Hdda).     

Performance of spin-component-scaled Møller-Plesset theory (SCS-MP2) for potential energy curves of noncovalent interactions

An examination of the performance of density-fitted, spin-component-scaled, second-order M?ller-Plesset theory (SCS-MP2), SCS-MP2 with parameters optimized for nucleic acids (SCSN-MP2), and their local-correlation variants, SCS-LMP2 and SCSN-LMP2, is presented for the sandwich and T-shaped benzene dimers, the methane-benzene and H(2)S-benzene complexes, and the methane dimer over entire potential energy curves. These are compared to benchmark-quality estimates of the complete-basis-set limit for coupled-cluster theory through perturbative triple excitations, CCSD(T)/CBS. With the exception of the methane dimer, SCSN-LMP2/CBS tends to outperform SCS-LMP2/CBS with maximum relative errors of 6 and 18%, respectively, at the optimal CCSD(T)/CBS intermolecular distances. For the methane dimer, errors for SCS(N)-(L)MP2/CBS remain in the 0.2-0.3 kcal mol(-1) range, corresponding to a larger relative error of 40-50%. Although the local MP2 methods perform very similarly to their conventional counterparts when aug-cc-pVTZ or larger basis sets are used, in the absence of counterpoise correction the local approximation becomes significantly worse for the aug-cc-pVDZ basis set. The changes due to local correlation approximations for the aug-cc-pVDZ basis are reduced when diffuse functions are neglected for hydrogen atoms.     

Deposition of90Sr and plutonium isotopes derived from the Chernobyl accident in Japan

To clarify environmental effects of the Chemobyl radionuclides, long-lived Chernobyl radioactivity (^239,240Pu,²³⁸Pu,²⁴¹Pu and⁹⁰Sr) in deposition samples in May 1986 was measured at 11 stations in Japan. Temporal variation of weekly deposition of⁹⁰Sr differed from that of volatile radionuclides such as¹³¹I and¹³⁷Cs, which may reflect the released process at Chernobyl. On the other hand, the geographical distributions of the monthly deposition of long-lived radionuclides were similar to those of volatile radionuclides, in which maximum deposits of⁹⁰Sr and plutonium were observed in Akita, a northwestern Japan Sea coast site of Honshu Island. Higher²⁴¹Pu deposition in most of the stations, as well as high²³⁸Pu/^239,240Pu activity ratios were observed. The²⁴¹Pu/²³⁸Pu activity ratios in deposition samples were nearly equal to that in the total release, which is clear evidence that Chernobyl-derived plutonium was transported to Japan in May 1986 together with volatile radionuclides although the contribution of Chernobyl Pu was about three orders of magnitude lower than¹³⁷Cs.     

Pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist

We propose a pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist. Unlike the original thermo–Cubic Interpolated Propagation Combined Unified Procedure (CIP‐CUP) method proposed by Himeno et al (Transactions of the Japan Society of Mechanical Engineers, Series B, 2003), we split the advection term of the governing equations into a conservation part and into the rest. The splitting of advection term has two advantages. One is the high degree of freedom in choosing discretization schemes such as central‐difference schemes, upwind schemes, and Total Variation Diminishing (TVD) schemes. The other is the ease of implementation on unstructured grids. The advantages enable the analyses of various flows such as turbulent and supersonic ones in actual complicated boundaries. Therefore, the solver is useful for practical analyses. The solver was validated on the following test cases: subsonic single‐phase flows, incompressible single‐phase turbulent flows, and incompressible gas‐liquid two‐phase flows. With unstructured grids, we obtained the equivalent results as the ones with structured grids. After the validations, subsonic jet impinging on a water pool was calculated and compared with experimental results. It was confirmed that the calculated results were consistent with the experimental ones.