Molecular elastic crystals exhibiting slow magnetic relaxations.

We report an elastic crystal of a copper(II) porphyrinato complex that exhibits slow magnetic relaxations and is a promising candidate for an external-force-responsive spin qubit.

Ultra-High-Capacity Lithium Metal Batteries Based on Multi-Electron Redox Reaction of Organopolysulfides including Conductive Organic Moieties.

Recently, organic polysulfides have been synthesized as cathode active materials exceeding the battery performance of sulfur. However, the conventional organic polysulfides have exhibited capacities lower than the theoretical capacity of sulfur because the π-organic moieties do not conjugate with the sulfur chains. In this work, the organopolysulfides, synthesized via inverse vulcanization using disulfide compounds, exhibited higher capacities equal to the theoretical capacity of sulfur because of enhanced electronic conductivity based on the conjugation between organic moieties and sulfur chains. Furthermore, the organopolysulfide including 1,3-dhitiol-2-thione moiety exhibited the highest capacity because of the enhanced electronic conductivity. This finding will pave the way to develop next-generation rechargeable batteries.

Ionic liquid-containing coordination polymer: solvent-free synthesis, incongruent melting, and glass formation.

An ionic-liquid-containing 2D coordination polymer was synthesized via a solvent-free reaction. The material exhibited incongruent melting at 112 °C, forming a solid-liquid mixture; further heating to 240 °C led to complete melting. Upon cooling, the melt transformed into a solid-liquid mixture, from which the coordination polymer was gradually recovered at ambient temperature. Rapid cooling (>200 °C s-1) of the melt resulted in complete vitrification at -28 °C.

Reactive sulfur species inhibit the migration of PDGF-treated vascular smooth muscle cells by blocking the reactive oxygen species-regulated Akt signaling pathway.

Vascular smooth muscle cell (VSMC) migration contributes to vascular remodeling after injury, whereas oxidative stress generated through dysfunctional redox homeostasis induces hypermigration, leading to arteriosclerosis. Platelet-derived growth factor (PDGF)-induced reactive oxygen species (ROS) serve as intracellular signaling molecules in VSMCs. Reactive sulfur species (RSS) may serve as a biological defense system because of the antioxidative properties of highly nucleophilic sulfane sulfur. However, insufficient information is available on its function in PDGF-induced VSMC migration. Here we show that PDGF significantly increased the levels of intracellular sulfane sulfur and that intracellular sulfane sulfur donors, donor 5a and Na2S4, inhibited the increase in ROS levels in PDGF-treated VSMCs and inhibited their migration. Consistent with the migration results, sulfane sulfur donors inhibited Akt phosphorylation, a downstream signaling molecule in the PDGF cascade, without affecting the autophosphorylation of PDGF receptor-ß. Further, sulfane sulfur donors inhibited vinculin and paxillin recruitment to the leading edge of VSMCs in response to PDGF to decrease focal adhesion formation. These findings suggest that RSS are required for PDGF-stimulated VSMC migration through the regulation of the ROS-regulated Akt pathway, which may contribute to focal adhesion formation. Our findings provide insight into RSS as novel regulators of vascular redox homeostasis.

Crystallization and fusion behaviors, observed by adiabatic calorimetry, of benzene confined in silica mesopores with uniform diameters.

Heat capacities and spontaneous enthalpy-relaxation effects of the benzene confined in silica MCM-41 and SBA-15 pores with uniform diameters were measured by high-precision adiabatic calorimetry. The fusion temperatures and fusion enthalpies determined were compared with the literature results of benzene confined within pores of CPG glasses. It was confirmed, from the observed spontaneous heat-release or -absorption effects, that there exists a non-crystallizing amorphous component of confined benzene, as reported previously. The pore-diameter dependence of fusion enthalpy observed was inconsistent with the previously proposed model which suggested that the non-crystallizing amorphous component is located on the pore wall in the form of a shell-like structure of a few nm in thickness. A very slow relaxation process corresponding to a translational-diffusion motion of molecule was observed, indicating that the benzene fills the pores incompletely along the pore channel. In addition, we found that the fusion enthalpy as a function of inverse pore-diameter dependence decreases steeply in the range of 60-10 nm in diameter while gradually in the range around 5 nm.

Stereoselective synthesis and NMR characterization of C-24 epimeric pairs of 24-alkyl oxysterols.

Two pairs of C-24 epimeric (24R)-/(24S)-24-hydroxy-24-methyl-5α-cholestan-3ß-yl acetates and (24R)-/(24S)-25-hydroxy-24-methyl-5α-cholestan-3ß-yl acetates as well as some related 24-ethyl oxysterol analogs were stereoselectively synthesized directly from the respective parent 24-alkyl sterols by a remote O-insertion reaction with 2,6-dichloropyridine N-oxide (DCP) in the presence of a catalytic amount of (5,10,15,20-tetramesitylporphrinate) ruthenium(II) carbonyl complex [Ru(TMP)CO] and HBr. ¹H- and ¹³C-NMR signals serving to differentiate each of the two epimeric pairs were interpreted. The C-24 alkyl oxysterols epimeric at C-24 were found to be effectively characterized by the aromatic solvent-induced shift (ASIS) by C5D5N, particularly for the difference in the ¹³C resonances in the substituted cholestane side chain. A method for differentiating the ¹H and ¹³C signal assignment of the terminal 26-/27-CH3 in the iso-octane side chain was also discussed on the basis of a combined use of the preferred conformational analysis and HMQC and HMBC techniques. The present method may be useful for determining the stereochemical configuration at C-24 of this type of 24-alkyl oxysterols.

Piezotolerance of the respiratory terminal oxidase activity of the piezophilic Shewanella violacea DSS12 as compared with non-piezophilic Shewanella species.

The facultative piezophile Shewanella violacea DSS12 is known to alter its respiratory components under the influence of hydrostatic pressure during growth, suggesting that it has a respiratory system that functions in adaptation to high pressure. We investigated the pressure- and temperature-dependencies of the respiratory terminal oxidase activity of the membrane of S. violacea relative to non-piezophilic Shewanella species. We observed that the activity in the membrane of S. violacea was more resistant to high pressure than those of non-piezophilic Shewanella even though DSS12 was cultured under atmospheric pressure. On the other hand, the temperature dependency of this activity was almost the same for all of the tested strain regardless of optimal growth temperature. Both high pressure and low temperature are expected to lower protein flexibility, causing a decrease in enzyme activity, but the results of this study suggest that the mechanism maintaining enzyme activity under high hydrostatic pressure is different from that at low temperature. Additionally, the responses of the activity to the pressure- and temperature-changes were independent of membrane lipid composition. Therefore, the piezotolerance of the respiratory terminal oxidases of S. violacea is perhaps dependent on the properties of the protein itself and not on the lipid composition of the membrane. Our observations suggest that S. violacea constitutively express piezotolerant respiratory terminal oxidases that serve adaptation to the deep-sea environment.

Anomalous dielectric behavior and thermal motion of water molecules confined in channels of porous coordination polymer crystals.

Guest water molecules confined in channels of porous coordination polymer crystals [Ln(2)Cu(3)(IDA)(6)]·nH(2)O (Ln = La, Nd, Sm, Gd, Ho, Er; IDA = [NH(CH(2)COO)(2)](2-); n ≈ 9) exhibited large dielectric constants (ε) and antiferroelectric behaviors at high temperatures (e.g., ε(Sm) ≈ 1300 at 400 K). In addition, plots of the temperature dependence of ε showed broad peaks at ∼170 K, below which ε became very small. These puzzling temperature dependences of ε are consistent with the results of molecular dynamics simulations, suggesting the "freezing of thermal motion" of water molecules at ∼170 K.

Roles of the C-terminal residues of calmodulin in structure and function.

Electrospray ionization mass spectrometry (ESI-MS), circular dichroism (CD), nuclear magnetic resonance (NMR) spectroscopy, flow dialysis, and bioactivity measurements were employed to investigate the roles of the C-terminal residues of calmodulin (CaM). In the present study, we prepared a series of truncated mutants of chicken CaM that lack four (CCMΔ4) to eight (CCMΔ8) residues at the C-terminal end. It was found that CCMΔ4, lacking the last four residues (M145 to K148), binds four Ca2+ ions. Further deletion gradually decreased the ability to bind the fourth Ca2+ ion, and CCMΔ8 completely lost the ability. Interestingly, both lobes of Ca2+-sturated CCMΔ5 showed instability in the conformation, although limited part in the C-lobe of Ca2+-saturated CCMΔ4 was instable. Moreover, unlike CCMΔ4, structure of the C-lobe in CCMΔ5 bound to the target displayed dissimilarity to that of CaM, suggesting that deletion of M144 changes the binding manner. Deletion of the last five residues (M144 to K148) and further truncation of the C-terminal region decreased apparent capacity for target activation. Little contribution of the last four residues including M145 was observed for structural stability, Ca2+-binding, and target activation. Although both M144 and M145 have been recognized as key residues for the function, the present data suggest that M144 is a more important residue to attain Ca2+ induced conformational change and to form a proper Ca2+-saturated conformation.

Surfactant-free solution synthesis of fluorescent platinum subnanoclusters.

We have demonstrated the first surfactant-free synthesis of fluorescent Pt nanoclusters in N,N-dimethylformamide (DMF) solution. The Pt nanoclusters consist of 4 to 6 Pt atoms. They form highly stable dispersions in water, under both acidic (pH 2) and basic conditions (pH 12), and at ionic strengths of 1 M NaCl.

Functionalized pyrolytic highly oriented graphite polymer film for surface-assisted laser desorption/ionization mass spectrometry in environmental analysis.

The pyrolytic highly oriented graphite polymer film (PGS) was first employed to analyze low-mass analytes in environmental analysis by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). PGS is a synthetic uniform and highly oriented graphite polymer film with high thermal anisotropic conductivity. We have found that negative ion mode SALDI-MS using oxidized PGS (PGS-SALDI-MS) can be used to detect [M-H]- ions from perfluorooctanoic acid (PFOA) and other perfluoroalkylcarboxylic acids when the PGS surface is modified with the cationic polymer polyethyleneimine (PEI). The signal intensity of PFOA when employing the PEI modification showed a ten-fold increase over that obtained from desorption/ionization on porous silicon (DIOS). PFOA was quantified using PGS-SALDI-MS and the calibration curve showed a wide linear dynamic range of response (20-1000 ppb). The combination of atmospheric pressure ionization and PGS (AP-PGS-SALDI) showed greater signal intensity than vacuum PGS-SALDI for deprotonated PFOA. Several other environmentally important chemicals, including perfluoroalkylsulfonic acid, pentachlorophenol, bisphenol A, 4-hydroxy-2-chlorobiphenyl, and benzo[a]pyrene, were also successfully used to evaluate PGS-SALDI-MS. In addition, we found that nonafluoro-1-butanesulfonic acid was able to produce protonated peptides in positive ion PGS-SALDI-MS, but that perfluoropentanoic acid and trifluoroacetic acid were not. It is suggested that perfluoroalkylsulfonic acids are better protonating agents than perfluoroalkylcarboxylic acids in SALDI-MS.