Formation of p-phenylenediamine-crown ether-[PMo12O40]4- salts

Electron transfer from the electron donor of p-phenylenediamine (PPD) to the electron acceptor of (H+)3[PMo12O40]3- forms a one-electron-reduced Keggin cluster of [PMo12O40]4-, bearing a S = 1/2 spin, while proton transfer from the proton donor of (H+)3[PMo12O40]3- to the proton acceptor of PPD yielded mono- and diprotonated cations of 4-aminoanilinium (HPPD+) and p-phenylenediammonium (H2PPD2+). By introduction of crown ether receptors during the crystallization process, supramolecular cations of (HPPD+)(crown ethers) and/or (H2PPD2+)(crown ethers) were successfully introduced into three new alpha-[PMo12O40]4- salts of (H2PPD2+)2([12]crown-4)4[PMo12O40]4- (1), (HPPD+)4([15]crown-5)4[PMo12O40]4- (2), and (HPPD+)2(H2PPD2+)([18]crown-6)4[PMo12O40]4- (3) as the countercation. The protonated states of PPD and molecular-assembly structures of the supramolecular cations depended on the size of the crown ethers. In salt 3, a novel mixed-protonated state of HPPD+ and H2PPD2+ was confirmed to be complexed in the cation structure. According to the changes in the cation structures, the anion arrangements were modulated from those of the two-dimensional layer for salt 1 to the isolated cluster for salts 2 and 3. The temperature-dependent magnetic susceptibilities of salts 1-3 were consistent with the isolated spin arrangements of [PMo12O40]4-. The electronic spectra of salts 1-3 indicated the intervalence optical transition from pentavalent Mo(V) to hexavalent Mo(VI) ions within the [PMo12O40]4- cluster. Temperature-dependent electron spin resonance spectra of salt 2 revealed the delocalization-localization transition of the S = 1/2 spin at 60 K. The spin on the [PMo12O40]4- cluster was localized on a specific Mo(V) site below 60 K, which was thermally activated with an activation energy of 0.015 eV.     

pH-responsive, self-assembling nanoparticle from a fullerene-tagged poly(L-glutamic acid) and its superoxide dismutase mimetic property

In this study, we describe the fabrication of novel fullerene-containing peptide-nanoparticles through self-assembly. A water-soluble, poly(l-glutamic acid)-attached fullerene was newly synthesized and the conformation and self-assembling property in water were examined by using circular dichroism, FTIR, UV, atomic force microscopy, and dynamic light scattering measurements. In the lower pH region (<6.8), the fullerene peptide self-assembles into nanoparticles that are ca. 100-200 nm in diameter. These nanoparticles are rich in alpha-helices, and stacking interaction of fullerene moieties contributes to the stability of the high-order structure. In addition, these particle sizes can be easily controlled by changing pH that results in causing the conformational transition of PLGA segment. Finally, the fullerene-containing nanoparticle is confirmed to be capable of removing the biologically important superoxide radical in comparison with the superoxide dismutase.     

Synthesis of alpha-amino acid precursors directly from aldehydes using masked acyl cyanide reagents and N,O-dialkylated hydroxylamines

A synthetic methodology for the synthesis of alpha-amino acid precursors directly from the corresponding aldehydes using N,O-dialkylated hydroxylamines and masked acyl cyanide (MAC) reagents was developed. The one-pot reaction can be carried out under mild conditions and without a separate purification step of the imino species. The method was applied to the synthesis of optically pure (+)-4-methylphenylglycine and the derivatives by using an Abiko-Masamune's tricyclic 1,2-oxazolidine as the chiral auxiliary.     

Synthesis and structural characterization of Al4Si2C5-homeotypic aluminum silicon oxycarbide, (Al6−xSix)(OyC5−y) (x∼0.8 and y∼1.6)

We have prepared a new layered oxycarbide, [Al_5.25(5)Si_0.75(5)][O_1.60(7)C_3.40(7)], by isothermal heating of (Al_4.4Si_0.6)(O_1.0C_3.0) at 2273 K near the carbon-carbon monoxide buffer. The crystal structure was characterized using X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The title compound is trigonal with space group R3?m (centrosymmetric), Z=3, and hexagonal cell dimensions a=0.32464(2) nm, c=4.00527(14) nm and V=0.36556(3) nm³. The atom ratios Al:Si were determined by EDX, and the initial structural model was derived by the direct methods. The final structural model showed the positional disordering of one of the three types of Al/Si sites. The reliability indices were R_wp=4.45% (S=1.30), R_p=3.48%, R_B=2.27% and R_F=1.25%. The crystal is composed of three types of domains with nearly the same fraction, one of which has the crystal structure of space group R3¯m. The crystal structure of the remaining two domains, which are related by pseudo-symmetry inversion, is noncentrosymmetric with space group R3m.     

Visualization and Quantification of Vascular Structure of Fruit Using Magnetic Resonance Microimaging

Three-dimensional magnetic resonance (MR) images of four kinds of fruit (Japanese apricot, peach, Japanese pear, and apple) were acquired throughout their growing periods (from April to August) to visualize and quantify their vascular structures. The vascular structures were emphasized using T ₁-weighted spin-echo or gradient-echo pulse sequences, visualized using a maximum-intensity projection technique, and quantified using an image-segmentation program. As a result, we demonstrated that the vascular volume changed almost in proportion to the whole volume and that larger fruits generally had larger proportionality constants. We therefore concluded that MR microimaging is a powerful tool for studies of the vascular structure of fruit.     

The molecular basis of myeloid malignancies

Myeloid malignancies consist of acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and myeloproliferative neoplasm (MPN). The latter two diseases have preleukemic features and frequently evolve to AML. As with solid tumors, multiple mutations are required for leukemogenesis. A decade ago, these gene alterations were subdivided into two categories: class I mutations stimulating cell growth or inhibiting apoptosis; and class II mutations that hamper differentiation of hematopoietic cells. In mouse models, class I mutations such as the Bcr-Abl fusion kinase induce MPN by themselves and some class II mutations such as Runx1 mutations induce MDS. Combinations of class I and class II mutations induce AML in a variety of mouse models. Thus, it was postulated that hematopoietic cells whose differentiation is blocked by class II mutations would autonomously proliferate with class I mutations leading to the development of leukemia. Recent progress in high-speed sequencing has enabled efficient identification of novel mutations in a variety of molecules including epigenetic factors, splicing factors, signaling molecules and proteins in the cohesin complex; most of these are not categorized as either class I or class II mutations. The functional consequences of these mutations are now being extensively investigated. In this article, we will review the molecular basis of hematological malignancies, focusing on mouse models and the interfaces between these models and clinical findings, and revisit the classical class I/II hypothesis.     

Anisotropic Dissociation of π–π Stacking and Flipping‐Motion‐Induced Crystal Jumping in Alkylacridones and Their Dicyanomethylene Derivatives

Ethylacridone ( 1 b ) and dicyanomethylenated acridones 2 a , b , d showed crystal‐jumping activity upon heating. This is the first example of thermosalient behavior in a simple aromatic ketone and its derivatives. A systematic investigation of the jumping behavior of derivatives with different alkyl chains by variable‐temperature X‐ray crystal‐structure analyses revealed the mechanism of this phenomenon. Anisotropic dissociation of π stacking in a dimer was important for inducing crystal jumping in 1 b , whereas the collective fluctuation/flipping motion of a dicyanomethylene unit induced crystal jumping in 2 .     

Human serum albumin incorporating synthetic hemes as an O2-carrying hemoprotein: control of O2-binding ability by heme structure

Incorporation of different structured synthetic hemes, 5,10,15,20-tetraphenylporphyrinatoiron(II) derivetives with a covalently linked proximal base [FeP( 1 ) to FeP( 7 )], into human serum albumin (HSA), provides seven types of albumin-heme hybrids (HSA-FeP) with different O₂-binding abilities. An HSA host absorbs a maximum of eight FeP molecules in each case. The obtained all HSA-FePs can reversibly bind and release O₂ under physiological conditions (in aqueous media, pH 7.3, 37°C) as similar as hemoglobin and myoglobin. The difference in the fence structures did not affect the O₂-binding parameters, however the axial histidine coordination significantly increased the O₂-binding affinity, which is ascribed to the low O₂-dissociation rate constants. The most remarkable effect of the heme structure appeared in the half-lifetime (τ_1/2) of the O₂-adduct complex. The dioxygenated rHSA-FeP( 4 ) showed an unusually long lifetime (τ_1/2: 25 hr at 37°C) which is ca. 13-fold longer than that of rHSA-FeP( 1 ).     

Synthesis of poly(ethynylplatinumporphyrin) and its application as an oxygen pressure-sensitive paint

5-(4-Trimethylsilyethynylphenyl)-10,15,20-triphenylplatinumporphyrin was synthesized and copolymerized with trimethylsilylpropyne to give a new high-molecular-weight porphyrin polymer. The polymer formed a smooth and tough coating on many types of surfaces. The coating showed a strong blue luminescence from the platinumporphyrin residue which was quenched in the presence of oxygen. The relationship of the luminescence intensity vs oxygen pressure displayed a remarkably high pressure sensitivity in the low oxygen pressure area, which was ascribed to the high oxygen permeability of the polymer.