X-ray structures of the Pseudomonas cichorii D-tagatose 3-epimerase mutant form C66S recognizing deoxy sugars as substrates.

Pseudomonas cichorii D-tagatose 3-epimerase (PcDTE), which has a broad substrate specificity, efficiently catalyzes the epimerization of not only D-tagatose to D-sorbose but also D-fructose to D-psicose (D-allulose) and also recognizes the deoxy sugars as substrates. In an attempt to elucidate the substrate recognition and catalytic reaction mechanisms of PcDTE for deoxy sugars, the X-ray structures of the PcDTE mutant form with the replacement of Cys66 by Ser (PcDTE_C66S) in complexes with deoxy sugars were determined. These X-ray structures showed that substrate recognition by the enzyme at the 1-, 2-, and 3-positions is responsible for enzymatic activity and that substrate-enzyme interactions at the 4-, 5-, and 6-positions are not essential for the catalytic reaction of the enzyme leading to the broad substrate specificity of PcDTE. They also showed that the epimerization site of 1-deoxy 3-keto D-galactitol is shifted from C3 to C4 and that 1-deoxy sugars may bind to the catalytic site in the inhibitor-binding mode. The hydrophobic groove that acts as an accessible surface for substrate binding is formed through the dimerization of PcDTE. In PcDTE_C66S/deoxy sugar complex structures, bound ligand molecules in both the linear and ring forms were detected in the hydrophobic groove, while bound ligand molecules in the catalytic site were in the linear form. This result suggests that the sugar-ring opening of a substrate may occur in the hydrophobic groove and also that the narrow channel of the passageway to the catalytic site allows a substrate in the linear form to pass through.

ß-d-Gulose.

The title compound, C6H12O6, a C-3 position epimer of d-galactose, crystallized from an aqueous solution, was confirmed as ß-d-pyran-ose with a (4) C 1 (C1) conformation. In the crystal, O-H⋯O hydrogen bonds between the hy-droxy groups at the C-1 and C-6 positions connect mol-ecules into a tape structure with an R 3 (3)(11) ring motif running along the a-axis direction. The tapes are connected by further O-H⋯O hydrogen bonds, forming a three-dimensional network.

Exploring spin states and ligand field splitting in metal complexes: a theoretical analysis of spin-orbital interactions and magnetic properties.

Metal complexes are pivotal in diverse fields due to their wide array of functionalities, including magnetism, conductivity, and photoresponsiveness. These functionalities are intricately linked to the phenomenon of ligand field splitting, yet controlling the magnitude of this splitting within metal complexes presents a significant challenge. This study aims to address this challenge by developing a novel 2D spectrochemical series, integrating two critical parameters: metal ions and ligands. Employing the DV-Xα molecular orbital method, we directly calculated ligand field splitting width, enabling a detailed assessment of energy splitting trends. Our results reveal that the magnitude of ligand field splitting, encompassing 17 metal types and 29 ligand types, can be precisely controlled. This represents a significant advancement over traditional spectrochemical series, such as those proposed by R. Tsuchida, which predominantly focus on either ligands or metals in isolation. Additionally, our study extends to the calculation of spin states in these metal complexes, contributing valuable insights for the development of magnetic materials. We demonstrate that the relative ligand field splitting and spin polarization can be used to predict spin states, offering a new perspective in material design and functionality. These findings not only enhance our understanding of ligand field splitting in metal complexes but also provide a comprehensive framework for predicting their electronic and magnetic properties, paving the way for innovative applications in material science and coordination chemistry.

Temperature-independent hole mobility of a smectic liquid-crystalline semiconductor based on band-like conduction.

A liquid-crystalline (LC) phenylterthiophene derivative, which exhibited an ordered smectic phase at room temperature, was purified by vacuum sublimation under a flow of nitrogen. During the sublimation process, thin plates with sizes of 1 mm grew on the surface of the vacuum tube. The crystals exhibited the same X-ray diffraction patterns as the ordered smectic phase of the LC state that was formed through a conventional recrystallization process by using organic solvents. Because of the removal of chemical impurities, the hole mobility in the ordered smectic phase of the vacuum-grown thin plates increased to 1.2×10(-1) cm(2) V(-1) s(-1) at room temperature, whereas that of the LC precipitates was 7×10(-2) cm(2) V(-1) s(-1). The hole mobility in the ordered smectic phase of the vacuum-sublimated sample was temperature-independent between 400 and 220 K. The electric-field dependence of the hole mobility was also very small within this temperature range. The temperature dependence of hole mobility was well-described by the Hoesterey-Letson model. The hole-transport characteristics indicate that band-like conduction affected by the localized states, rather than a charge-carrier-hopping mechanism, is a valid mechanism for hole transport in an ordered smectic phase.

Transition metals doped effects for the crystal stabilization of the cerium oxides with the first principle calculation.

In recent years, hydrogen energy has been attracting attention, and the hydrogen gas production using solar thermal energy has been conducted. The studies of Kodama et al. were reported that the cyclic reaction can efficiently produce the hydrogen gas through a two-step thermal redox reaction with the cerium oxide. The transition metal doping into the cerium oxide improved the reaction efficiency. We considered the doping effect on the thermal two-step redox reaction. As a result of the calculation by the DV-Xα method, it was clarified that the doped cerium oxide becomes a strong bond, the large BOP value without changing the ceria crystal structure in the two-step thermal redox reaction. The theoretical calculation results corresponded to the reaction efficiency improvement of the thermal reaction in experimental results.

Methyl α-l-sorboside monohydrate.

Methyl l-sorboside monohydrate, C7H14O6·H2O, was prepared from the rare sugar l-sorbose, C6H12O6, and crystallized. It was confirmed that methyl l-sorboside formed α-pyran-ose with a 2 C 5 conformation and crystallized with one water molecule of crystallization. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network. The unit-cell volume of the title compound, methyl l-sorboside monohydrate, is 481.13 (2) Å3 (Z = 2), which is about 108.16 Å3 (29.0%) greater than that of half the amount of the chemical α-l-sorbose [745.94 (2) Å3 (Z = 4)].

Ethyl α-l-sorboside.

Ethyl l-sorboside, C8H16O6, was prepared from the rare sugar l-sorbose, C6H12O6, and crystallized. It was confirmed that ethyl l-sorboside formed α-pyran-ose with a 2 C 5 conformation. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network. The unit-cell volume of the title ethyl α-l-sorboside is 940.63 Å3 (Z = 4), which is about 194.69 Å3 (26.1%) bigger than that of l-sorbose [745.94 Å3 (Z = 4)].

Crystal structure of ß-d,l-fructose.

The title compound, C6H12O6, was crystallized from an aqueous solution of equimolar mixture of d- and l-fructose (1,3,4,5,6-penta-hydroxy-hexan-2-one, arabino-hexulose or levu-lose), and it was confirmed that d-fructose (or l-fructose) formed ß-pyran-ose with a (2) C 5 (or (5) C 2) conformation. In the crystal, two O-H⋯O hydrogen bonds between the hy-droxy groups at the C-1 and C-3 positions, and at the C-4 and C-5 positions connect homochiral mol-ecules into a column along the a axis. The columns are linked by other O-H⋯O hydrogen bonds between d- and l-fructose mol-ecules, forming a three-dimensional network.

Crystal structure of ß-d,l-allose.

The title compound, C6H12O6, a C-3 position epimer of glucose, was crystallized from an equimolar mixture of d- and l-allose. It was confirmed that d-allose (l-allose) formed ß-pyran-ose with a (4) C 1 ((1) C 4) conformation in the crystal. In the crystal, molecules are linked by O-H⋯O hydrogen bond, forming a three-dimensional framework. The cell volume of the racemic ß-d,l-allose is 739.36 (3) Å(3), which is about 10 Å(3) smaller than that of chiral ß-d-allose [V = 751.0 (2) Å(3)].

Crystal structure of 6-de-oxy-α-l-psico-furan-ose.

The title compound, C6H12O5, was crystallized from an aqueous solution of 6-de-oxy-l-psicose (6-de-oxy-l-allulose, (3S,4S,5S)-1,3,4,5-tetra-hydroxy-hexan-2-one), and the mol-ecule was confirmed as α-furan-ose with a (3) T 4 (or E 4) conformation, which is a predominant tautomer in solution. This five-membered furan-ose ring structure is the second example in the field of the 6-de-oxy-ketohexose family. The cell volume of the title compound [742.67 (7) Å(3), Z = 4 at room temperature] is only 1.4% smaller than that of ß-d-psico-pyran-ose, C6H12O6 (753.056 Å(3), Z = 4 at room temperature).

Crystal structure of ß-d,l-psicose.

The title compound, C6H12O6, a C-3 position epimer of fructose, was crystallized from an aqueous solution of equimolar mixture of d- and l-psicose (1,3,4,5,6-penta-hydroxy-hexan-2-one, ribo-2-hexulose, allulose), and it was confirmed that d-psicose (or l-psicose) formed ß-pyran-ose with a (2) C 5 (or (5) C 2) conformation. In the crystal, an O-H⋯O hydrogen bond between the hy-droxy groups at the C-3 and C-2 positions connects homochiral mol-ecules into a column along the b axis. The columns are linked by other O-H⋯O hydrogen bonds between d- and l-psicose mol-ecules, forming a three-dimensional network. An intra-molecular O-H⋯O hydrogen bond is also observed. The cell volume of racemic ß-d,l-psicose [763.21 (6) Å(3)] is almost the same as that of chiral ß-d-psicose [753.06 Å(3)].

New Sesquiterpene Lactone Dimer, Uvedafolin, Extracted from Eight Yacon Leaf Varieties (Smallanthus sonchifolius): Cytotoxicity in HeLa, HL-60, and Murine B16-F10 Melanoma Cell Lines.

Uvedafolin, 1, a new sesquiterpene lactone dimer, was isolated from the leaves of Smallanthus sonchifolius with five related compounds, 2-6, and their cytotoxicity was assessed against three tumor cell lines (HeLa, HL-60, B16-F10 melanoma). The stereostructure of 1 was newly elucidated by ESI-TOF-MS, 1D/2D NMR, and single-crystal X-ray diffraction. Dimers 1 and 2 had the most effective IC50 values, 0.2-1.9 µM, against the three tumor cell lines when compared with monomers 3-6 (IC50 values 0.7-9.9 µM) and etoposide (IC50 values 0.8-114 µM). The ester linkages of two sets of monomers, uvedalin, 5, and sonchifolin, 6, for 1, and enhydrin, 4, and sonchifolin, 6, for 2, as well as the acetyl group at the C-9 position, were essential for the high cytotoxicity. Dimers 1 and 2 would have potential as anticancer agents.

Gene expression profiling identifies a set of transcripts that are up-regulated inhuman testicular seminoma.

Seminoma constitutes one subtype of human testicular germ cell tumors and is uniformly composed of cells that are morphologically similar to the primordial germ cells and/or the cells in the carcinoma in situ. We performed a genome-wide exploration of the genes that are specifically up-regulated in seminoma by oligonucleotide-based microarray analysis. This revealed 106 genes that are significantly and consistently up-regulated in the seminomas compared to the adjacent normal tissues of the testes. The microarray data were validated by semi-quantitative RT-PCR analysis. Of the 106 genes, 42 mapped to a small number of specific chromosomal regions, namely, 1q21, 2p23, 6p21-22, 7p14-15, 12pll, 12p13, 12q13-14 and 22q12-13. This list of up-regulated genes may be useful in identifying the causative oncogene(s) and/or the origin of seminoma. Furthermore, immunohistochemical analysis revealed that the seminoma cells specifically expressed the six gene products that were selected randomly from the list. These proteins include CCND2 and DNMT3A and may be useful as molecular pathological markers of seminoma.

Tuning of Charge Density Wave Strengths by Competition between Electron-Phonon Interaction of Pd(II)-Pd(IV) Mixed-Valence States and Electron Correlation of Ni(III) States in Quasi-One-Dimensional Bromo-Bridged Ni-Pd Mixed-Metal MX Chain Compounds Ni(1)(-)(x)()Pd(x)()(chxn)(2)Br(3).

A series of single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal MX chain compounds Ni(1)(-)(x)()Pd(x)()(chxn)(2)Br(3) (chxn = 1(R),2(R)-diaminocyclohexane) have been obtained by electrochemical oxidation methods of the mixed methanol solutions of parent Ni(II) complex [Ni(chxn)(2)]Br(2) and Pd(II) complex [Pd(chxn)(2)]Br(2) with various mixing ratios. To investigate the competition between the electron correlation of the Ni(III) states (or spin density wave states) and the electron-phonon interaction of the Pd(II)-Pd(IV) mixed-valence states (or charge density wave states) in the Ni-Pd mixed-metal compounds, IR, Raman, ESR, XP, and Auger spectra have been measured. The IR, resonance Raman, XP, and Auger spectra show that the Pd(II)-Pd(IV) mixed-valence states are influenced and gradually approach the Pd(III) states with the increase of the Ni(III) components. This means that in these compounds the electron-phonon interaction in the Pd(II)-Pd(IV) mixed-valence states is weakened with the strong electron correlation in the Ni(III) states.

A New Anion-Trapping Radical Host, [(Cu-dppe)3 {hat-(CN)6 }]2+ .

Anions PF6- and CF3 SO3- are trapped by the new radical host [(Cu-dppe)3 {hat-(CN)6 }]2+ , which was synthesized in a one-pot reaction from a copper(I) source, hat-(CN)6 , and dppe in acetone. The trapped salts have been characterized both in solution and in the solid state (see picture: A- : PF6- , CF3 SO3- ). hat-(CN)6 =hexaazatriphenylene hexacarbonitrile; dppe=1,2-bis(diphenylphosphanyl)ethane.

Transformation of potassium Lindquist hexaniobate to various potassium niobates: solvothermal synthesis and structural evolution mechanism.

This paper introduces the formation reactions and reaction mechanisms of a series of potassium niobates from a potassium salt of the Lindquist hexaniobate [Nb6O19](8-) ion under solvothermal conditions. The structure and particle morphology of the potassium niobate product can be controlled easily with the reaction solution alkalinity using this solvothermal process. KNb3O8 with a plate-like morphology, K4Nb6O17·4.5H2O with a plate-like morphology, a new phase of K2Nb2O6·H2O with fibrous morphology, KNbO3 perovskites with cubic morphology are obtained at pH = 5.5, and in 0.3, 0.5, 1.0 mol L(-1) KOH solutions at 230 °C, respectively. The reaction conditions are much milder than those in the normal hydrothermal process. Furthermore, the K2Nb2O6·H2O fibers can be topotactically transformed into KNbO3 fibers, Nb2O5 fibers after H(+)-exchange-treatment, and LiNbO3 fibers after Li(+)-exchange-treatment by heat-treatments at 730, 560, and 520 °C, respectively. The formation reaction and structure of these potassium niobates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), Raman spectra and TG-DTA. The formation mechanism of this series of potassium niobates from the [Nb6O19](8-) precursor is systematically explained via the correlation between the octahedrons [NbO6] sharing forms in the precursor structure and in the product structures.

Crystal structures of rare disaccharides, α-D-glucopyranosyl ß-D-psicofuranoside, and α-D-galactopyranosyl ß-D-psicofuranoside.

The crystal structures of α-D-glucopyranosyl ß-D-psicofuranoside and α-D-galactopyranosyl ß-D-psicofuranoside were determined by a single-crystal X-ray diffraction analysis, refined to R(1)=0.0307 and 0.0438, respectively. Both disaccharides have a similar molecular structure, in which psicofuranose rings adopt an intermediate form between (4)E and (4)T(3). Unique molecular packing of the disaccharides was found in crystals, with the molecules forming a layered structure stacked along the y-axis.

Catalytic reaction mechanism of Pseudomonas stutzeri L-rhamnose isomerase deduced from X-ray structures.

L-Rhamnose isomerase (L-RhI) catalyzes the reversible isomerization of L-rhamnose to L-rhamnulose. Pseudomonas stutzeril-RhI, with a broad substrate specificity, can catalyze not only the isomerization of L-rhamnose, but also that between D-allose and D-psicose. For the aldose-ketose isomerization by L-RhI, a metal-mediated hydride-shift mechanism has been proposed, but the catalytic mechanism is still not entirely understood. To elucidate the entire reaction mechanism, the X-ray structures of P. stutzeril-RhI in an Mn(2+)-bound form, and of two inactive mutant forms of P. stutzeril-RhI (S329K and D327N) in a complex with substrate/product, were determined. The structure of the Mn(2+)-bound enzyme indicated that the catalytic site interconverts between two forms with the displacement of the metal ion to recognize both pyranose and furanose ring substrates. Solving the structures of S329K-substrates allowed us to examine the metal-mediated hydride-shift mechanism of L-RhI in detail. The structural analysis of D327N-substrates and additional modeling revealed Asp327 to be responsible for the ring opening of furanose, and a water molecule coordinating with the metal ion to be involved in the ring opening of pyranose.

Universal spectrochemical series of six-coordinate octahedral metal complexes for modifying the ligand field splitting.

We studied a novel universal spectrochemical series of six-coordinated octahedral 3d transition metal complexes, which can be used for any combination of central metal atom and ligand molecules. A two dimensional spectrochemical series could be used to estimate the ligand field splitting energy of not only known compounds but also the unknown compounds. Therefore, it should be possible to control the physical properties, such as the electronic and magnetic properties and the optical phenomena of octahedral transition metal complexes by modifying the ligand field splitting.

Reverse photochromic behavior of an iron-magnesium complex.

We have obtained a novel heterobimetallic iron-magnesium complex, (THF)4Mg(mu-Br)2FeBr2 (THF = tetrahydrofuran), which showed reverse photochromism in THF. The response exhibited in this system is associated with d-orbital splitting of the Fe atom and a change in the molecular aggregation state (dimerization).