Search

The major cytoskeleton protein actin undergoes cyclic transitions between the monomeric G-form and the filamentous F-form, which drive organelle transport and cell motility. This mechanical work is driven by the ATPase activity at the catalytic site in the F-form. For deeper understanding of the actin cellular functions, the reaction mechanism must be elucidated. Here, we show that a single actin molecule is trapped in the F-form by fragmin domain-1 binding and present their crystal structures in the ATP analog-, ADP-Pi-, and ADP-bound forms, at 1.15-Å resolutions. The G-to-F conformational transition shifts the side chains of Gln137 and His161, which relocate four water molecules including W1 (attacking water) and W2 (helping water) to facilitate the hydrolysis. By applying quantum mechanics/molecular mechanics calculations to the structures, we have revealed a consistent and comprehensive reaction path of ATP hydrolysis by the F-form actin. The reaction path consists of four steps: 1) W1 and W2 rotations; 2) P G –O 3B bond cleavage; 3) four concomitant events: W1–PO 3 − formation, OH − and proton cleavage, nucleophilic attack by the OH − against P G , and the abstracted proton transfer; and 4) proton relocation that stabilizes the ADP-Pi–bound F-form actin. The mechanism explains the slow rate of ATP hydrolysis by actin and the irreversibility of the hydrolysis reaction. While the catalytic strategy of actin ATP hydrolysis is essentially the same as those of motor proteins like myosin, the process after the hydrolysis is distinct and discussed in terms of Pi release, F-form destabilization, and global conformational changes.

All-solid-state batteries with Li metal anode can address the safety issues surrounding traditional Li-ion batteries as well as the demand for higher energy densities. However, the development of solid electrolytes and protective anode coatings possessing high ionic conductivity and good stability with Li metal has proven to be a challenge. Here, we present our informatics approach to explore the Li compound space for promising electrolytes and anode coatings using high-throughput multi-property screening and interpretable machine learning. To do this, we generate a database of battery-related materials properties by computing $$\hbox {Li}^+$$ Li + migration barriers and stability windows for over 15,000 Li-containing compounds from Materials Project. We screen through the database for candidates with good thermodynamic and electrochemical stabilities, and low $$\hbox {Li}^+$$ Li + migration barriers, identifying promising new candidates such as $$\hbox {Li}_9\hbox {S}_3$$ Li 9 S 3 N, $$\hbox {LiAlB}_2\hbox {O}_5$$ LiAlB 2 O 5 , $$\hbox {LiYO}_2$$ LiYO 2 , $$\hbox {LiSbF}_4$$ LiSbF 4 , and $$\hbox {Sr}_4\hbox {Li}(\hbox {BN}_2)_3$$ Sr 4 Li ( BN 2 ) 3 , among others. We train machine learning models, using ensemble methods, to predict migration barriers and oxidation and reduction potentials of these compounds by engineering input features that ensure accuracy and interpretability. Using only a small number of features, our gradient boosting regression models achieve $$\mathrm {R}^2$$ R 2 values of 0.95 and 0.92 on the oxidation and reduction potential prediction tasks, respectively, and 0.86 on the migration barrier prediction task. Finally, we use Shapley additive explanations and permutation feature importance analyses to interpret our machine learning predictions and identify materials properties with the largest impact on predictions in our models. We show that our approach has the potential to enable rapid discovery and design of novel solid electrolytes and anode coatings.

Li-rich type manganese oxides are one of the most promising cathodes for lithium-ion batteries in recent years; thanks to their high energy density. In these cathodes, partial substitution of manga...

2,3-Butandione 2-monoxime (BDM) is a widely used myosin inhibitor with an unclear mode of action. In this report, we investigated the mechanism of BDM oxime group nucleophilic reactivity on the phosphoester bond of ATP. BDM increased the ATPase activity of skeletal myosin subfragment 1 (S1) under conditions in which ATP cleavage is the rate-limiting step (K+, EDTA-ATPase activity of native S1 and Mg2+-ATPase activity of trinitrophenylated S1 and partially unfolded S1). Furthermore, the effect of BDM on the S1-bound adenosine 5′-(β,γ-imido) triphosphate (AMPPNP) 31P NMR spectrum suggests that BDM changes the microenvironment around the phosphorus atoms of myosin-bound nucleotide. A computational search for the BDM-binding site in the adenosine 5′-[γ-thio] triphosphate (myosin–ATPγS) complex predicted that BDM is located adjacent to the nucleotide on myosin. Therefore, we propose that the BDM oxime group catalytically assists in ATP cleavage, thereby enhancing the ATPase activity of myosin in a manner analogous to pralidoxime-mediated reactivation of organophosphate-inactivated acetylcholinesterase. This is the first study suggesting that oxime provides catalytic assistance for ATP cleavage by an ATP-hydrolyzing enzyme.

Li2MnO3, an electrode material for Li ion batteries, belongs to the C2/m space group and is known to have a cubic-close-packed (ABC...) layered structure, in which the transition-metal layer is supposed to have an ordered atomic arrangement with Li atoms at the 2b site and Mn atoms at the 4g site. However, recently, it has been reported that this compound usually does not exhibit such an ideal structure and instead contains a large number of structural defects, not only stacking faults but also mixing of Li and Mn atoms between the 2b and 4g sites. To elucidate the effect of such structural defects on the electrochemical behavior, we examined the crystal structure of Li2MnO3 synthesized at various temperatures by simultaneously analyzing the stacking faults and cation mixing using FAULTS, a Rietveld code. Our examination showed that the crystals consist of both disordered and ordered domains; the disordered domains contain a large number of stacking faults along the c axis and have considerable Li/Mn atomic mixing within the transition-metal layer, whereas the ordered domains have almost no defects. At low synthesis temperatures, the disordered domains are dominant. However, the ordered domains increase at the expense of the disordered domains above 770 °C and become dominant at higher temperatures. It is also found that the degree of cation mixing in the disordered domains remains almost constant irrespective of synthesis temperature. The crystalline defects such as stacking faults or Li/Mn cation mixing are expected to promote the formation of smooth Li percolation paths. The decreasing of the disordered domains leads to dramatically decreased capacity. This indicates that the observed capacities of Li2MnO3 can be determined by the relative amounts of the ordered/disordered domains in the structure.

We examined the crystal structures of Li2(NixMn1-x)O3(-δ) (x = 0, 1/10, 1/6, and 1/4) to elucidate the relationship between the structure and electrochemical performance of the compounds using neutron and synchrotron X-ray powder diffraction analyses in combination. Our examination revealed that these crystals contain a large number of stacking faults and exhibit significant cation mixing in the transition-metal layers; the cation mixing becomes significant with an increase in the Ni concentration. Charge-discharge measurements showed that the replacement of Mn with Ni lowers the potential of the charge plateau and leads to higher charge-discharge capacities. From a topological point of view with regard to the atomic arrangement in the crystals, it is concluded that substituting Mn in Li2MnO3 with Ni promotes the formation of smooth Li percolation paths, thus increasing the number of active Li ions and improving the charge-discharge capacity.

The oxidation/reduction behaviours of lattice oxygen and transition metals in a Li-rich manganese-based layered oxide Li[Li0.25Ni0.20Mn0.55]O1.93 are investigated by using hard X-ray photoelectron spectroscopy (HAX-PES). By making use of its deeper probing depth rather than in-house XPS analyses, we clearly confirm the formation of O- ions as bulk oxygen species in the active material. They are formed on the 1st charging process as a charge compensation mechanism for delithiation and decrease on discharging. In particular, the cation-anion dual charge compensation involving Ni and O ions is suggested during the voltage slope region of the charging process. The Ni ions in the material are considered to increase the capacity delivered by a reversible anion redox reaction with the suppression of O2 gas release. On the other hand, we found structural deterioration in the cycled material. The O- species are still observed but are electrochemically inactive during the 5th charge-discharge cycle. Also, the oxidation state of Ni ions is divalent and inactive, although that of Mn ions changes reversibly. We believe that this is associated with the structural rearrangement occurring after the activation process during the 1st charging, leading to the formation of spinel- or rocksalt-like domains over the sub-surface region of the particles.

In attempt to experimentally evaluate hydration/solvation of phosphoric compounds in aqueous solution, partitioning of phosphoric compounds from an aqueous solution to an organic solvent has been quantified. Transfer of phosphates from an aqueous solution into octanol was greatly enhanced by addition of alkylamine as an amphiphilic extractant. This alkylamine/octanol system exhibited amine basicity, and thus the pH of solution was controlled by equilibration with buffer. Further, enthalpy changes of the transfers of ATP and ADP from water to the alkylamine/octanol were estimated from van’t Hoff analysis, and these enthalpy changes depended on ionization enthalpy of buffer. This result suggests that the transfers are accompanied with protonation of phosphoric ions and deprotonation of alkylamine. Finally, the partition coefficients of ATP, ADP, AMP, and Pi were estimated under the pH-controlled condition at 25 °C. The partition coefficients depended on the pH of aqueous phase and the net charge of phosphoric compounds. Therefore, the transfer is likely to be determined by electrostatic interaction between phosphoric ion and amine. The solvent system with a nucleotide-uptake capacity may partly mimic the function of ATP-binding proteins.

Delithiation and lithiation behaviors of ordered spinel LiNi0.5Mn1.5O4 and disordered spinel LiNi0.4Mn1.6O4 were investigated by using in situ (in operando) 7Li NMR and ex situ 6Li MAS NMR spectroscopy. The in situ 7Li monitoring of the ordered spinel revealed a clear appearance and subsequent disappearance of a new signal from the well-defined phase Li0.5Ni0.5Mn1.5O4, suggesting the two-phase reaction processes among Li1.0Ni0.5Mn1.5O4, Li0.5Ni0.5Mn1.5O4, and Li0.0Ni0.5Mn1.5O4. Also, for the disordered spinel, Li0.5Ni0.4Mn1.6O4 was identified with a broad distribution in Li environment. High-resolution 6Li MAS NMR spectra were also acquired for the delithiated and lithiated samples to understand the detailed local structure around Li ions. We suggested that the nominal Li-free phase Li0.0Ni0.5Mn1.5O4 can accommodate a small amount of Li ions in its structure. The tetragonal phases Li2.0Ni0.5Mn1.5O4 and Li2.0Ni0.4Mn1.6O4, which occurred when the cell was discharged down to 2.0 V, were very different in the Li environment from each other. It is found that 6, 7Li NMR is highly sensitive not only to the Ni/Mn ordering in LiNi0.5Mn1.5O4 but also to the valence changes of Ni and Mn on charge-discharge process.

The Mycobacterium tuberculosis (M. tuberculosis) enoyl-acyl carrier protein reductase (mtInhA) is an attractive enzyme and a thoroughly studied target for tuberculosis therapy. In this study, to identify novel structure-activity relationships (SARs) of mtInhA inhibitors, a series of diphenyl ether derivatives were designed based on the matched molecular pair (MMP) method, and the binding energies of these compounds were subsequently estimated by in silico structure-based drug screening (SBDS) to provide more useful data. Consequently, the 10 unique candidate compounds (KEM1-KEM10) were identified and assessed for the inhibition of mtInhA enzymatic activity, in vitro antibiotic effects against model mycobacteria and toxicity level on both intestinal bacteria and mammalian cells. Among the compounds tested, phenyl group (KEM4) and 2-fluorobenzyl group (KEM7) substitutions produced preferable inhibitory effects on mtInhA enzymatic activity relative to those provided by a furyl group (KES4: base compound) at the terminal of the compound, and KEM7 inhibited the growth of the mycobacteria strain with a lower IC50 value. Moreover, most of the candidate compounds exhibited neither inhibition of the growth of enterobacteria nor toxic effects on mammalian cells, though KEM10 exhibited toxicity against cultured MDCK cells. The structural and experimental information concerning these mtInhA inhibitors identified through MMP-based in silico screening will likely contribute to the lead optimisation of novel antibiotics for M. tuberculosis.

Rutile-type FeOF is a promising cathode for lithium-ion batteries, because it has a relatively large theoretical capacity of 885 mAh g −1 in eco-friendly iron-based cathodes. Although it is difficult to synthesize by conventional solid-state synthesis methods, it can be quickly synthesized by the roll-quenching method. The quick synthesis method is suitable to reduce the produce cost, but also to avoid the fluorine gas release during synthesis procedure. The obtained FeOF by roll-quenching method has kept some crystallinities, and provides a large discharge capacity (900 mAh g −1 ) between 0.7 and 4.0 V. The charge and discharge reaction mechanism was investigated by structural analyses.

To identify novel antibiotics against Mycobacterium tuberculosis, we performed a hierarchical structure-based drug screening (SBDS) targeting the enoyl-acyl carrier protein reductase (InhA) with a compound library of 154,118 chemicals. We then evaluated whether the candidate hit compounds exhibited inhibitory effects on the growth of two model mycobacterial strains: Mycobacterium smegmatis and Mycobacterium vanbaalenii. Two compounds (KE3 and KE4) showed potent inhibitory effects against both model mycobacterial strains. In addition, we rescreened KE4 analogs, which were identified from a compound library of 461,383 chemicals through fingerprint analysis and genetic algorithm-based docking simulations. All of the KE4 analogs (KES1-KES5) exhibited inhibitory effects on the growth of M. smegmatis and/or M. vanbaalenii. Based on the predicted binding modes, we probed the structure-activity relationships of KE4 and its analogs and found a correlative relationship between the IC50 values and the interaction residues/LogP values. The most potent inhibitor, compound KES4, strongly and stably inhibited the long-term growth of the model bacteria and showed higher inhibitory effects (IC50 = 4.8 μM) than isoniazid (IC50 = 5.4 μM), which is a first-line drug for tuberculosis therapy. Moreover, compound KES4 did not exhibit any toxic effects that impede cell growth in several mammalian cell lines and enterobacteria. The structural and experimental information of these novel chemical compounds will likely be useful for the development of new anti-TB drugs. Furthermore, the methodology that was used for the identification of the effective chemical compound is also likely to be effective in the SBDS of other candidate medicinal drugs.

Free heme, the protein-unbound form of heme, has both toxic and regulatory effects on cells. To detect free heme at low concentrations, we developed a heme sensor using fluorescently labeled heme oxygenase-1 (HO-1), an enzyme that catalyzes oxidative heme degradation and has a high affinity for heme. The response of the heme sensor is based on the fluorescence quenching that occurs when heme binds to the enzyme. Each of the three fluorescently labeled HO-1s exhibits a 1:1 binding stoichiometry and an absorption spectrum similar to that of the heme complex of the wild-type HO-1. Titration of the labeled proteins with hemin resulted in fluorescence quenching in a hemin concentration-dependent manner, presumably due to an energy transfer from the fluorophore to the heme bound to HO-1. The sensor showed a potent affinity for heme with a dissociation constant in the low nanomolar range and a high selectivity for heme. Based on the linear response of the sensor to heme, we performed a fluorometric microplate assay. The sensor was able to selectively detect free heme but did not respond to heme bound to native hemoglobin. This assay will be a useful tool for determination of free heme in biological samples containing protein-bound heme.

A new rearrangement reaction of spirocyclic cyclobutane N-halo aminals is described. This process, promoted by treatment of the aminals with N-halosuccinimides (NXS, X = Br or Cl), efficiently produces bicyclic amidines by a pathway involving initial N-halogenation of one of the aminal nitrogens followed by cyclobutane ring expansion through 1,2-C-to-N migration with simultaneous N-X bond cleavage.

Highly crystallized perovskite-type NaFeF3 has been investigated as the cathode for sodium-ion batteries through the roll-quench method. In the charge–discharge measurement, the first discharge capacity was 197 mAh g−1 at a rate of 0.076 mA cm−2 between 1.5 V and 4.5 V. Reversible Fe2+/Fe3+ redox reaction on cycle was confirmed by XPS. The ex situ XRD measurements for charged or discharged NaFeF3 pellets revealed the reversible vibration on cycle, due to the structure strength and flexibility of the corner-sharing matrix. The peak intensities of (1 1 2) and (0 0 4) were changed with accompanying insertion/extraction of sodium, suggesting the extracted sodium has returned to the original 4c site on discharge.

Glucosyltransferase (GTF)-I from cariogenic Streptococcus sobrinus elongates the α-(1→3)-linked glucose polymer branches on the primer dextran bound to the C-terminal glucan-binding domain. We investigated the GTF-I-catalyzed glucan synthesis reaction in the absence of the primer dextran. The time course of saccharide production during dextran-independent glucan synthesis from sucrose was analyzed. Fructose and glucose were first produced by the sucrose hydrolysis. Leucrose was subsequently produced, followed by insoluble glucan [α-(1→3)-linked glucose polymers] after a lag phase. High levels of intermediate nigerooligosaccharide series accumulation were characteristically not observed during the lag phase. The results from the enzymatic activity of the acceptor reaction for the nigerooligosaccharide with a degree of polymerization of 2-6 and methyl α-D-glucopyranoside as a glucose analog indicate that the activity increased with an increase in the degree of polymerization. The production of insoluble glucan was numerically simulated using the fourth-order Runge-Kutta method with the kinetic parameters estimated from the enzyme assay. The simulated time course provided a profile similar to that of experimental data. These results define the relationship between the kinetic properties of GTF-I and the time course of saccharide production. These results are discussed with respect to a mechanism that underlies efficient glucan synthesis.

Glucosyltransferases (GTFs) secreted by mutans streptococci and some other lactic acid bacteria catalyze glucan synthesis from sucrose, and possess a C-terminal glucan-binding domain (GBD) containing homologous, directly repeating units. We prepared a series of C-terminal truncated forms of the GBD of Streptococcus sobrinus GTF-I and studied their binding to dextran by isothermal titration calorimetry. The binding of all truncates was strongly exothermic. Their titration curves were analyzed assuming that the GBD recognizes and binds to a stretch of dextran chain, not to a whole dextran molecule. Both the number of glucose units constituting the dextran stretch (n) and the accompanying enthalpy change (DeltaH degrees ) are proportional to the molecular mass of the GBD truncate, with which the Gibbs energy change calculated by the relation DeltaG degrees = -RT ln K (R, the gas constant; T, the absolute temperature; K, the binding constant of a truncate for a dextran stretch of n glucose units) also increases linearly. For the full-length GBD (508 amino acid residues), n = 33.9, K = 4.88 x 10(7) M-1, and DeltaH degrees = -289 kJ mol-1 at 25 degrees C. These results suggest that identical, independent glucose-binding subsites, each comprising 14 amino acid residues on average, are arranged consecutively from the GBD N-terminus. Thus, the GBD binds tightly to a stretch of dextran chain through the adding up of individually weak subsite/glucose interactions. Furthermore, the entropy change accompanying the GBD/dextran interaction as given by the relation DeltaS degrees = (DeltaG degrees - DeltaH degrees)/T has a very large negative value, probably because of a loss of the conformational freedom of dextran and GBD after binding.

We recently reported a novel heme sensor using fluorescently labeled heme oxygenase-1; however, its inherent enzyme activity would be a potential obstacle in quantifying heme in biological samples. Here, we found that mutation of the catalytically important residue, Asp140, with histidine in the sensor not only diminished the heme degradation activity but also increased heme binding affinity. The sensor with a visible fluorophore was also found to be beneficial to avoid background emission from endogenous substance in biological samples. By using the improved heme sensor, we succeeded in quantifying free heme in rat hepatic samples for the first time.

Oxidative cleavage of cyclobutanols using PIDA, which leads to efficient entry of γ-hydroxy ketones, is described. When using 2-substituted cyclobutanols, γ-substituted γ-hydroxy ketones are obtained through regioselective C–C bond cleavage.

Acquisition of substantial amounts of CO32-, HPO42- and other impurities is universally encountered in bioapatites from mammals. To date, however, there is a paucity of information about the stoichiometry and, on that basis, solubility product of dentin mineral. In this report, we summarize our experimental approach toward the determination of the stoichiometry model and thermodynamic solubility products of human dentin apatites. Dentin samples were collected separately from the coronal portion of permanent premolars (extracted for orthodontic reasons) and exfoliated deciduous teeth. Both pooled materials were pulverized with an agate-mortar, and then plasma-ashed at approx. 60°C to remove the organic matter. The stoichiometry model selected for these crystals was (Ca) 5-x (Mg) q (Na) u (HPO4) v (CO3) w (PO4) 3-y (OH) 1-z. These stoichiometric coefficients were analytically determined by assessing separately the labile or surface pools of the ionic species on the crystal surface and their stable pools in the bulk crystal lattice. The dentin mineral was equilibrated in dilute phosphoric solutions (100mg/100ml) at 25°C for a maximum of 28 days under constant partial pressures of CO2. The results showed that there are appreciable differences in the crystal stoichiometry between the permanent and deciduous dentin mineral and that the solubility product constants (KDN) were 4.11×10-45 for permanent dentin and 1.74×10-43 for deciduous dentin, which were determined under 1.8% CO2/N2. Notably, the solubility properties of the dentin mineral remained relatively constant in the range of 1.0 through 3.3% CO2/N2, whereas the discrete solubility data were obtained below and above the corresponding partial pressure of CO2.

Glucosyltransferase-I (GTF-I: 175 kDa) of a cariogenic bacterium, Streptococcus sobrinus 6715, mediates the conversion of water-soluble dextran (alpha-1,6-glucan) into a water-insoluble form by making numerous alpha-1,3-glucan branches along the dextran chains with sucrose as the glucosyl donor. The structures and catalytic properties were compared for two GTF-I fragments, GTF-I' (138 kDa) and GS (110 kDa). Both lack the N-terminal 84 residues of GTF-I. While GTF-I' still contains four of the six C-terminal repeats characteristic of streptococcal glucosyltransferases, GS lacks all of them. Electron microscopy of negatively stained samples indicated a double-domain structure for GTF-I', consisting of a spherical head with a smaller spherical tail, which was occasionally seen as a long extension. GS was seen just as the head portion of GTF-I'. In the absence of dextran, both fragments simply hydrolyzed sucrose with similar K(m) and k(cat) values at low concentrations (5 mM). At higher sucrose concentrations (10 mM), however, GTF-I' exhibited glucosyl transfer activity to form insoluble alpha-1, 3-glucans. So did GS, but less efficiently. Dextran increased the rate and efficiency of the glucosyl transfer by GTF-I'. On removal of the C-terminal repeats of GTF-I' by mild trypsin treatment, this dextran-stimulated transfer was completely lost and the dextran-independent transfer became less efficient. These results indicate that the N-terminal two-thirds of the GTF-I sequence are organized as a structurally and functionally independent domain to catalyze not only sucrose hydrolysis but also glucosyl transfer to form alpha-1,3-glucan chains, although not efficiently; the C-terminal repeat increases the efficiency of the intrinsic glucosyl transfer by the N-terminal domain as well as rendering the whole molecule primer-dependent for far more efficient insoluble glucan synthesis.

The present study was undertaken to investigate the effects of systemic HEBP (1-hydroxyethylidene-1, 1-bisphosphonate) administration on the alveolar bone structure at the intraradicular region of rat lower molars. Male Wistar rats (about 100 g b.w.) were divided into three groups: (a) animals kept with drinking water containing 1% HEBP throughout the housing periods covering 4 days through 8 weeks; (b) animals given the same HEBP-containing water during the initial 4 weeks, thereafter being kept with HEBP-free drinking water for various periods (4-28 days) ; and (c) animals kept free from HEBP during the corresponding periods as the control group. The tooth specimens were examined by histometric analysis in conjunction with H.E., van Gieson, and TRAP stainings; or by microradiography. The results obtained evidenced that: 1) systemic administration of 1% HEBP stimulated the outgrowth of osteoid due to hindrance of mineralization onto the deposited bone matrix and osteoclastic resorption activity, giving rise to obliteration of the periodontal space (development of focal ankylosis) ; and 2) after cessation of the HEBP administration, TRAP-positive osteoclasts penetrated into the ankylosed areas, leading to reconstruction of the periodontal structure within the following 3 to 4 weeks. It is pertinent that the use of HEBP to rat provides an experimental model for pathogenesis of the osteoid-mediated ankylosis and its reversible recovery.

Lithium-rich layered oxides (LLOs) have attracted much attention as high-capacity electrodes in lithium-ion batteries. Especially, LLOs are known to show high performance at high temperature. The transition metal (TM) migrates from the TM layer to the Li layer in the LLO active material during the charge−discharge cycle, which complicates our understanding of its electrochemical properties. In this study, we applied X-ray diffraction spectroscopy (XDS) for acquiring quantitative data on TM migration depending on the crystallographic site in Li1.2−xNi0.13Co0.13Mn0.53O2, and we discuss their influence on the electrochemical properties at 40 and −10 °C. The XDS analysis shows that both Mn and Ni in the TM layer migrate to the Li layer during the charge process and return during the discharge process. This reversible migration, observed at 40 °C, corresponds to a high capacity. On the other hand, the operation at −10 °C decreases the degree of TM migration as well as the charge−discharge capacity. In particular, Mn and Ni hardly migrate to the TM layer and remain at the Li layer at the end of discharge. This clogged interlayer space, which would lower the Li+ diffusion, accounts for the capacity drop.

Introduction LiFePO4 is a promising cathode material for lithium-ion batteries1 as it exhibits high rate performance.2 The origin of the high rate performance exemplified in LiFePO4 should provide design principles for further development of high rate cathode materials. The (dis)charge reaction of LiFePO4 proceeds through a two phase behavior between Li-rich Li1-αFePO4 (LFP) and Li-poor LiβFePO4 (FP).3 Under high rate cycling, we revealed the formation of a metastable phase of Li x FePO4 (x = 0.6–0.75) (L x FP) which acts as a buffer layer between LFP and FP.4 However, the detailed reaction between LFP and FP during high rate cycling has not fully been understood due to short lifetime of metastable L x FP phase. To investigate the phase transition mechanism, with respect to L x FP phase, cycling at low temperatures was performed because metastable L x FP phase might have long lifetime to fully capture its spatial-temporal formation. Phase transition mechanism is analyzed by operando time-resolved X-ray diffraction (TR-XRD) measurements at low temperatures. Experimental Three-electrode aluminum-laminated pouch-type cells were fabricated for operando TR-XRD measurements. LiFePO4/C particles were synthesized by hydrothermal methods.4 The working electrode comprised a composite mixture of LiFePO4/C, carbon black (Denka), and polyvinylidene fluoride (Kureha) at a ratio of 75:15:10 (wt%) and coated on aluminum foil current collectors. Lithium foil was used as counter and reference electrodes. The electrolyte was 1 mol dm–3 of LiPF6 dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate (3:7 volume ratio, Battery Grade, Kishida). operando TR-XRD measurements were performed in transmission mode at the beam line BL28XU at SPring-8 (Japan). The wavelength of X-ray was 0.9998Å. The cells were set at fixed temperatures (–5, 5 and 25 °C) using temperature-controlled jackets,5 and were charged and discharged at constant rates of 1C (170 mA g–1), 5C (850 mA g–1) and 10C (1700 mA g–1) between 2.0 and 4.3 V versus Li/Li+ for 5 cycles. Results and Discussions In the charge-discharge cycle at 25ºC and rate of 1C, operando TR-XRD pattern looks typical of the two-phase reaction between the LFP and FP phases. LFP 211 and 020 diffractions disappeared and the FP 211 and 020 diffractions simultaneously appeared, as the cell was charged. Conversely, the FP diffractions disappeared and the LFP diffractions appeared, as the cell was discharged. On the other hand, the behavior of the operando TR-XRD patterns in the first charging at –5°C is different from that at 25°C. The intensity bridge between LFP and FP 211 was observed. This indicates the formation of the LxFP phase even in the first charging. The diffraction peaks of FP phase disappeared and the peak of the LxFP phase at 19.4° appeared as the cells were discharged. These results suggest that the first charging process is different from the first discharging process except for the condition of 1C rate and 25°C. Moreover, at 10C rates and –5°C, the fact that the discharging finishes at the single LxFP phase suggests that the phase transition between the LxFP and LFP phases is slow. The difference of phase transition kinetics between LFP/LxFP and LxFP/FP cause the initial irreversible capacity at high rate, and/or low temperature conditions. References (1) Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc., 1997, 144, 1188. (2) Meethong, N.; Kao, Y.-H.; Carter, W. C.; Chiang, Y.-M. Chem. Mater., 2010, 22, 1088. (3) Yamada, A.; Koizumi, H.; Nishimura, S. I.; Sonoyama, N.; Kanno, R.; Yonemura, M.; Nakamura, T.; Kobayashi, Y. Nat. Mater., 2006, 5, 357. (4) Orikasa, Y.; Maeda, T.; Koyama, Y.; Murayama, H.; Fukuda, K.; Tanida, H.; Arai, H.; Matsubara, E.; Uchimoto, Y.; Ogumi, Z. J. Am. Chem. Soc., 2013, 135, 5497. (5) Takahashi, I.; Murayama, H.; Sato, K.; Naka, T.; Kitada, K.; Fukuda, K.; Koyama, Y.; Arai, H.; Matsubara, E.; Uchimoto, Y.; Ogumi, Z. J. Mater. Chem. A, 2014, 2, 15414. Acknowledgement This study was partially supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) Project under the auspices of New Energy and Industrial Technology Development Organization (NEDO), Japan.

1. Introduction Li-rich type (manganese) oxides are one of the most featured cathodes for lithium ion batteries in recent years, owing to their high capacity and cyclability. In these cathodes, partial substitution of manganese by other transition metals such as Ni and Co has been proposed and shown to be effective in improving the performance, [1] however, the role of such metals in the battery performance has not been clarified in detail. We have synthesized Ni ion substituted Li excess manganese oxides (Li2Mn1-xNixO3) as a simple model of Li2MeO3 phase in solid solution cathode to understand the effect of introduced Ni by using the combination of in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction spectroscopy (XDS) analysis. Diffraction anomalous fine structure (DAFS) spectra are achieved by XDS analysis, that there were quantitatively showed potential-dependent transbilayer migration of nickel and manganese and their reversibility. 2. Experimental procedure The active material of nickel substituted Li2MnO3 (Li2Mn1-x NixO3, x = 0 ~ 0.25) was prepared from solid phase calcination at 1173 K for 12 h in air. The working electrode consisted of active material (80 wt.%), acetylene black (10 wt.%) and polyvinylidene difluoride (PVdF) binder (10 wt.%), coated on aluminum current foil. The electrochemical measurements of the electrode were employed using aluminum pouch type cells, metallic lithium as counter and reference electrodes, 1 mol dm-3 LiPF6 in a 3:7 mixture of EC/DMC, and a polyolefin film as a separator. The electrochemical charge and discharge tests were performed at room temperature and the potential range was between 2.0 and 4.8 V. XAS measurements were performed by the three-electrode cell with charging and discharging processes (in Operando). The XAS measurements of the Ni-K and Mn-K edge region were performed using a solid-state detector at beamlines BL28XU in SPring-8 (Hyogo, Japan). The XDS measurements were conducted at beamline BL28XU, SPring-8, Japan. A two-dimensional Pilatus detector (Dectris Co., Ltd.) was mounted onto an arm of a multi-axis goniometer and was used to measure the diffraction profile, and two ionization chamber was used for the absorption correction of the DAFS spectra. 3. Results and Discussion The obtained X-ray absorption near edge structure (XANES) region spectra at N-K energy region of Li2Mn1-x NixO3 (x = 0.25) in the 1st charging and discharging processes are shown in Fig. 1. The edge energy was shifted to high energy, which is suggested that Ni element function as a charge compensation species. However the end of charging region around 4.7 V to 4.8 V was shifted to low energy as seen in previous XAS report [2], which means the reduction of nickel on average in this region. As our group have published before,[3] XANES-like spectra only from selected sites (i.e. DAFS spectra) can be extracted from the XDS analysis. Fig. 2 shows the DAFS spectra of initial sample. The Ni-K edge XANES-like spectra shows that there was cation mixing in the lithium layer of the pristine material. In contrast, Mn-K edge XANES-like spectra shows that manganese mostly occupied in transition metal layer. XDS analysis of the fully charged sample indicated that Ni element further migrated to the lithium layer. These analytical approaches are important to understand the metal migration behavior as a function of operation potential together with the charge compensation mechanism during electrochemical charging and discharging. References [1] Thackeray, M. M.et al., J. Mater. Chem. 2007, 17, 3112. [2] Ito, A. et al., J. Power Sources 2011, 196, 6828. [3] Kawaguchi, T. et al., J. Synchrotron Rad. 2014, 21, 1247. Acknowledgement This work was supported by RISING of NEDO. Fig. 1 In situ Ni-K edge XAS spectra at 1st charging to 4.5V (a), irreversible plateau region (b), end of charging region 4.7-4.8 V (c), discharging to 2.0 V (d). Fig. 2 DAFS spectra of Ni-K edge XANES-like spectra (a) and Mn-K edge XANES-like spectra (b). Figure 1

High capacity cathode materials of lithium ion secondary battery are desirable to apply to the large-scaled energy devices such as electric vehicles or electricity storage systems. Recently, lithium-rich layered materials such as Li2MnO3 and Li2RuO3 are attended as interesting cathode materials because of their a few times larger theoretical capacity than that of LiCoO2 [1].The reaction mechanism of the lithium-rich cathodes has not been fully understood, especially at the high potential. In this study, Li2MnO3 and Li2RuO3 electrodes were prepared, and the electronic structure change of Li2MnO3 and Li2RuO3 were investigated by using operandosoft X-ray absorption spectroscopy under charge-discharge reaction of these electrodes. The cathode materials were synthesized by solid-state reaction method. Li2MnO3 was prepared from a stoichiometric amount of LiOH-H2O and MnO2. They were dispersed in acetone and ground by a ball milling machine for 3 hours at a speed of 400 rpm using 2 mm ZrO2 beads as grinding media. After drying, the mixture powder was pressed into pellets (10 mm diameter.) and heated at 450 °C for 24 hours in air and then calcined at 400 °C for 48 hours. Li2RuO3 was prepared from LiOH-H2O and RuO2in the same way, however, heated at 1000 °C for 15 hours in air and then ground for 3 hours before calcined at 900 °C for an hour. The cathode for operando X-ray absorption measurements was prepared from a paste by mixing 80 wt% of as-prepared cathode active materials, 10 wt% of acetylene black and 10 wt% of polyvinylidene difluoride binder in 1-methyl-2-pyrrolidone solvent. This paste was coated on the platinum-sputtered silicon nitride thin film. Li4Ti5O12 was used as the counter electrode material and 1 mol/L LiPF6 in an acetonitrile solvent was used as an electrolyte. The operando soft X-ray absorption spectroscopy measurement was carried out at BL27SU of SPring-8. The oxygen K-edge XANES spectra for Li2MnO3 and Li2RuO3 during first charge reaction were measured. For the charge reaction of Li2MnO3, the peaks located at 529.5 eV and 532.0 eV were progressively weaken and broadened (Figure 1a). It implies that the main reaction during the charge process is the oxygen evolution because of the small contribution of Mn 3d - O 2p orbital. For Li2RuO3 (Figure 1b), on the other hand, the peaks at 529.5 eV and 532.0 eV were shifted to the lower energy during the delithiated process from x=2.00 to x=1.00 in LixRuO3 and these peaks were sharpen from x=1.00 to x=0.48. In the Ru L3-egde XANES spectra, the peak was shifted to the higher energy from x=2.00 to x=1.00, however not changed from x=1.00 to x=0.48. These results suggest that the Li2RuO3 charge reaction includes two process, (1) the oxidized reaction of Ru4+→Ru5+, (2) O2 charge compensation owing to the hybridization state between Ru 4d and O 2porbital. This work revealed the contribution of the Ru-O hybrid orbital during the charge process directly and was a guide to design the high-capacity cathode materials in the future. Reference [1] M. Sathiya, K. Ramesha, G. Rousse, D. Foix, D. Gonbeau, A. S. Prakash, M. L. Doublet, K. Hemalatha, and J.-M. Tarascon, Chem. Mater. 25(2013), 1121−1131

LiNi0.5Mn1.5O4 (LNMO) is a promising positive electrode material for lithium ion batteries because it shows a high potential of 4.7 V vs. Li/Li(+). Its charge-discharge reaction includes two consecutive phase transitions between LiNi0.5Mn1.5O4 (Li1) ↔ Li0.5Ni0.5Mn1.5O4 (Li0.5) and Li0.5 ↔ Ni0.5Mn1.5O4 (Li0) and the complex transition kinetics that governs the rate capability of LNMO can hardly be analyzed by simple electrochemical techniques. Herein, we apply temperature-controlled operando X-ray absorption spectroscopy to directly capture the reacting phases from -20 °C to 40 °C under potential step (chronoamperometric) conditions and evaluate the phase transition kinetics using the apparent first-order rate constants at various temperatures. The constant for the Li1 ↔ Li0.5 transition (process 1) is larger than that for the Li0.5 ↔ Li0 transition (process 2) at all the measured temperatures, and the corresponding activation energies are 29 and 46 kJ mol(-1) for processes 1 and 2, respectively. The results obtained are discussed to elucidate the limiting factor in this system as well as in other electrode systems.

Lys-83 in the heavy chain of rabbit skeletal muscle myosin is rapidly and stoichiometrically modified by trinitrobenzene sulfonate. Other authors claimed that the half-stoichiometric trinitrophenylation of Lys-83 in myosin in the presence of PPi was correlated to a Pro/Ser microheterogeneity at the 78th residue position in the heavy chain [Miyanishi, T., Maita, T., Matsuda, G., & Tonomura, Y. (1982) J. Biochem. 91, 1845-1853]. However, our recent studies with chymotryptic subfragment 1 (S1) instead of myosin showed no such correlation between the half-stoichiometric trinitrophenylation and the Pro/Ser microheterogeneity [Komatsu, H. & Tawada, K. (1993) J. Biol. Chem. 268, 16974-16978]. Since the global structure of the head portion of myosin is different from that of chymotryptic S1 that lacks DTNB light chain, it could be argued that the difference is due to the structural difference between chymotryptic S1 and myosin. We hence reexamined the situation with myosin, and obtained the same results as found with S1: (i) Lys-83 in myosin was half-stoichiometrically trinitrophenylated in the presence of PPi, although it was stoichiometrically modified in the absence of PPi; (ii) there was a Pro/Ser microheterogeneity at the 78th position in the myosin heavy chain, which was not correlated to the half-stoichiometric trinitrophenylation of Lys-83 in the presence of PPi.

Genetically encoded tags attached to proteins of interest are widely exploited for proteome analysis. Here, we present Tb(3+)-binding peptides (TBPs) which can be used for both luminescent measurements and affinity purification of proteins. TBPs consist of acidic amino acid residues and tryptophan residues which serve as Tb(3+)-binding sites and sensitizers for Tb(3+) luminescence, respectively. The Tb(3+) complexes of TBPs fused to a target protein exhibited luminescence characteristic of Tb(3+) by excitation of the tryptophan residue, and fusion proteins fused to one of the TPBs were successfully isolated from Escherichia coli cell lysate by affinity chromatography with a Tb(3+)-immobilized solid support.

Oxidative cleavage of cyclobutanols using PIDA, which leads to efficient entry of γ-hydroxy ketones, is described. When using 2-substituted cyclobutanols, γ-substituted γ-hydroxy ketones are obtained through regioselective C–C bond cleavage.

Glucosyltransferase (GTF)-I from cariogenic Streptococcus sobrinus elongates the α-(1→3)-linked glucose polymer branches on the primer dextran bound to the C-terminal glucan-binding domain. We investigated the GTF-I-catalyzed glucan synthesis reaction in the absence of the primer dextran. The time course of saccharide production during dextran-independent glucan synthesis from sucrose was analyzed. Fructose and glucose were first produced by the sucrose hydrolysis. Leucrose was subsequently produced, followed by insoluble glucan [α-(1→3)-linked glucose polymers] after a lag phase. High levels of intermediate nigerooligosaccharide series accumulation were characteristically not observed during the lag phase. The results from the enzymatic activity of the acceptor reaction for the nigerooligosaccharide with a degree of polymerization of 2-6 and methyl α-D-glucopyranoside as a glucose analog indicate that the activity increased with an increase in the degree of polymerization. The production of insoluble glucan was numerically simulated using the fourth-order Runge-Kutta method with the kinetic parameters estimated from the enzyme assay. The simulated time course provided a profile similar to that of experimental data. These results define the relationship between the kinetic properties of GTF-I and the time course of saccharide production. These results are discussed with respect to a mechanism that underlies efficient glucan synthesis.

A novel 2-step synthesis of oxazole-4-carboxylates from aldehydes was developed, which is characterized by the utilization of 3-oxazoline-4-carboxylates as synthetic intermediates. The facile preparation of 4-keto-oxazole derivatives from 3-oxazoline-4-carboxylates based on their interesting reactivity toward Grignard reagents is also described.

A novel transformation of phenols bearing a benzylic tert-alcohol moiety, e.g. (I) and (III) is described.

A novel 2-step synthesis of oxazole-4-carboxylates from aldehydes was developed, which is characterized by the utilization of 3-oxazoline-4-carboxylates as synthetic intermediates. The facile preparation of 4-keto-oxazole derivatives from 3-oxazoline-4-carboxylates based on their interesting reactivity toward Grignard reagents is also described.

The reaction of 1-(p-hydroxyaryl)cyclobutanols and phenyl iodide(III) diacetate in hexafluoroisopropanol and water produced spiro cyclohexadienone lactones via a domino reaction.

1. Introduction Nickel substituted manganese spinel LiNi0.5Mn1.5O4 (LNMO) shows high rate capability even it consist of micron-sized particles.[1] This is in contrast to LiFePO4 where only nano-sized particles show high rate performance. For the designing of high performance batteries, it is important to understand the phase transition mechanism of the micron-sized LNMO that is inseparably connected with the rate capability.[2] As the micron-sized LNMO particles is expected that the existence of possible intermediate states between the phases (namely Li1, Li1/2 and Li0) are captured by operando XRD while TEM analysis shows the existence of the phase transition front. In this study, we revealed the factor of reaction kinetics from phase transition behavior of the LNMO by operando (1 C and 5 C) synchrotron X-ray diffraction (XRD) measurement, and transmission electron microscopy (TEM) analysis. 2. Experimental procedure LNMO powder used as an active material has primary and secondary particle sizes of around 1 and 5-10 µm, respectively. The working electrode consisted of LNMO (80 wt.%), acetylene black (10 wt.%) and polyvinylidene difluoride (PVdF) binder (10 wt.%), coated on aluminum current foil. The electrochemical measurements of the electrode were employed using aluminum pouch type cells, metallic lithium as counter and reference electrodes, 1 mol dm-3 LiPF6 in a 3:7 mixture of EC/DMC, and a polyolefin film as a separator. The electrochemical charge and discharge tests were performed at room temperature and the potential range was between 3.5 and 5.0 V. The time-resolved XRD (TR-XRD) measurements were conducted at the BL28XU and BL46XU of SPring-8, Hyogo, Japan. The incident X-ray of 12.4 keV (0.100 nm wavelength) was used. We measured the diffractions in the region around the 115 peak of LNMO. The data acquisition time was 0.5 s and discharge tests were employed at rate of 1 or 5 C. The TEM was employed to analyze the particle morphology of initial LiNi0.5Mn1.5O4 powder and Li0.25Ni0.5Mn1.5O4 obtained by 1 C charging. Electron diffraction (ED) analysis and electron energy-loss spectroscopy (EELS) were also performed to analyze crystal structure and intraparticle distribution of the reacting material. 3. Results and Discussion Fig. 1 shows the XRD patterns obtained during the transition between Li1 and Li1/2, and Li1/2 and Li0 at charging process. When two symmetric peak profiles using the Gaussian functions are assumed for these phases at a region of two phases existence, the experimentally obtained intensity in between the two peaks is larger than the calculated intensity. It’s suggesting that there are minor diffractions with intermediate d values in addition to major ones of the phases. A good fit is obtained assuming two additional diffraction components, implying the existence of intermediates in between the phases. Compared to the homogeneous morphology of the pristine LNMO particle, cracks, stripes, lattice defects and regions of different contrast are observed in the charged sample as shown in Fig. 2. With ex-situ TEM analysis the coexistence of the two phases in primary particles is shown, suggesting that the phase front movement is slow and that the minor diffractions observed in operando XRD are originated from solid-solution domains at the phase transition front of Li x Ni0.5Mn1.5O4. At 5 C rate single phase transition behavior is observed for both Li1 and Li0 phases. References [1] X. Ma, et al., J. Electrochem. Soc., 2010, 157, A925. [2] T. Ichitsubo et al., J. Mater. Chem. A, 2013, 1, 14532. [3] H. Arai et al., J. Mater. Chem. A, 2014, 2, 15414. Acknowledgement This work was supported by RISING of NEDO. Figure captions Fig. 1 XRD profiles of a LiNi0.5Mn1.5O4 electrode in 1 C charging. Two two-phase coexistence regions are fitted with four Gaussian functions. Fig. 2 TEM image and ED pattern of (a) LiNi0.5Mn1.5O4(pristine) and (b) Li0.25Ni0.5Mn1.5O4 electrode sample obtained by 1 C rate charging. Figure 1

Nickel-substituted manganese spinel LiNi0.5Mn1.5O4 (LNMO) is a promising 5 V class positive electrode material for lithium-ion batteries. As micron-sized LNMO particles show high rate capability in its two-phase coexistence regions, the phase transition mechanism is of great interest in understanding the electrode behavior at high rates. Here, the phase transition dynamics of LixNi0.5Mn1.5O4 is elucidated on high rate charging–discharging using operando time-resolved X-ray diffraction (TR-XRD). The TR-XRD results indicate the existence of intermediate states, in addition to the thermodynamically stable phases, and it is shown that the origin of such intermediate states is ascribed to the solid-solution domains at the phase transition front, as supported by the analysis using transmission electron microscopy coupled with electron energy-loss spectroscopy. The phase transition pathways dependent on the reaction rate are shown, together with possible explanation for this unique transition behavior.

Proteolytic myosin subfragment 1 (S1) is known to be partially unfolded in its 50-kDa subdomain by mild heat treatment at 35 degrees C [Burke et al. (1987) Biochemistry 26, 1492-1496]. Here, we report that this partial unfolding is accompanied by aggregation of S1 protein. Characteristics of the aggregate thus formed were: (i) formation of transparent sediment under centrifugation at 183,000 x g; (ii) amyloid-like, dye-binding properties such as Congo red-binding and Thioflavin T fluorescence enhancement; (iii) a uniformly sized spherical appearance in electron micrographs; and (iv) sensitivity to tryptic digestion. Gel filtration analysis of the aggregation process indicates that the spheroid was formed through an intermediate oligomeric stage. The aggregate inhibited spontaneous aggregation of an isolated 50 kDa fragment into a large amorphous mass. The remaining native regions in the partially unfolded S1 were probably responsible for this effect. These results show that, unlike the 50-kDa fragment, the partially unfolded S1 molecules do not form amorphous aggregates but assemble into spherical particles. The native regions in partially unfolded S1 may be a determinant of aggregate morphology.

In this communication, we summarized our recent experimental approaches to an unsettled issue, i.e., the nature and role of an acidic precursor in enamel mineralization. The objectives we specially focused our attention on are: the composition, structure and high resolution images of enamel crystals at various developmental stages, thermodynamic and kinetic consideration of octacalcium phosphate (OCP) vs hydroxyapatite (HA) precipitation in physiological media simulating the enamel fluid, reversible changes in the composition and structure of OCP, effects of fluoride at low concentrations and enamel proteins on OCP hydrolysis, and adsorption of enamel proteins onto OCP and fluoridated hydrolysates at neutral pH and room temperature. On the basis of all experimental evidence, we propose that enamel crystal growth comprises two events: the two-dimensional growth of an OCP-like precursor in a narrow outermost zone adjacent to the ameloblasts and the subsequent overgrowth of apatite units on the template under discrete fluid environment in the underlying region distant from the cell layer. The experimental data also support the concept that the whole process of enamel mineralization is modulated substantially through interaction between enamel proteins and crystals including the acidic precursor.

Butanol-induced inhibition of K-EDTA-ATPase of myosin subfragment 1 proceeded by biphasic kinetics, consisting of rapid and slow inactivations. The extent of the rapid inactivation, which was estimated by extrapolating the process of slow inactivation to zero time of the incubation period, was saturated with butanol concentration. Recovery of activity by dilution in the rapid phase indicates that the rapid process is reversible. The slow inactivation was concomitant with a partial denaturation of the 50 kDa domain of S1, which was detected by limited tryptic digestion. Other alcohols (methanol, ethanol, propanol and hexanol) also inhibited the K-EDTA-ATPase in the rapid phase. The Ki decreased with an increase in the number of methylene groups of alcohol. When K-EDTA-ATPase activity in the rapid phase was plotted against viscosity, surface tension or dielectric constant, the curves were different for each of the various alcohol solutions. The rapid inactivation appears to be caused by a binding of the alkyl group to S1, rather than by solvent effects. The kinetics of rapid butanol inhibitions indicate that butanol reduces the maximum activity of ATPase but enhances an apparent affinity of S1 with ATP. These indications suggest that alcohol stabilizes S1.KATP intermediate. The rapid K-EDTA-ATPase inhibition was observed at the same alcohol concentration where S1 Mg-ATPase was activated.