Block copolystyrene derivatives having flexible alkylsulfonated side chains and hydrophobic alkoxy chains as a proton exchange membrane for fuel cell application

A series of block copolystyrene derivatives, poly{[4‐(4‐sulfobutyloxy)styrene]_x‐block‐[4‐(n‐butoxystyrene)]_y} (PSBOS_x‐b‐PnBOS_y), containing a flexible alkylsufonated side chain and hydrophobic alkoxy chain with various ion exchange capacities (IECs) have been synthesized based on living anionic polymerization. The resulting crosslinked membranes were prepared using 4,4′‐methylene‐bis[2,6‐bis(hydroxyethyl)phenol] as the crosslinker in the presence of methanesulfonic acid. The crosslinked PSBOS_2.2‐b‐PnBOS₁ membrane with IEC of 2.89 mequiv g^?1 displays a high proton conductivity (0.01 S cm^?1) at 30% relative humidity and 80 °C, which is comparable to that of Nafion. The well‐developed phase separation and the continuous hydrophilic domains in the crosslinked PSBOS_2.2‐b‐PnBOS₁ membranes have been observed in a transmission electron microscope image. Moreover, the dynamic mechanical analysis measurement and Fenton's reagent testing show that the crosslinked PSBOS_x‐b‐PnBOS_y membranes have good mechanical properties and oxidative stability. These results indicate that the introduction of flexible alkylsulfonated side chains to the polystyrene main chains positively affect both the proton conductivity and oxidative stability. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis, structure, and conformational mobility of a vaulted trans-bis(o-aminophenolato)platinum(II) complex

The synthesis, structure, and conformational mobility of a trans-bis(aminophenolato)platinum(II) complex bearing a dodecamethylene bridge, [Pt(L)] (1) [H ₂ L = N,N′-Dimethyl-N,N′-bis(2-hydroxyphenylmethyl)dodecane-1,12-diamine] are described. The 2D NMR and X-ray diffraction analysis revealed that the complex has a “reversed U”-shaped syn conformation in the solution state, which is mainly due to steric congestion of the vaulted structure and hydrogen bonding at the bis[(o-aminomethyl)phenolato] coordination site, while the complex unit is packed in the crystalline state with “Z-shaped” anti-conformation due to highly regulated molecular arrangement by 3D CH-π and hydrogen bonding interactions.     

Advances in Artificial Cell Membrane Systems as a Platform for Reconstituting Ion Channels

An artificial cell membrane that is composed of bilayer lipid membranes (BLMs) with transmembrane proteins incorporated within them represents a well‐defined system for the analysis of membrane proteins, especially ion channel proteins that are major targets for drug design. Because the BLM system has a high compatibility with recently developed cell‐free expression systems, it has attracted attention as a next‐generation drug screening system. However, three issues associated with BLM systems, i. e., their instability, the need for non‐volatile organic solvents and a low efficiency of ion channel incorporation, have limited their use as a drug screening platform. In this personal account, we discuss our recent approaches to address these issues based on microfabrication. We also discuss the potential for using the BLM system combined with cell‐free expression systems as a drug screening system for future personalized medicine.     

Chemical Synthesis of O‐Glycosylated Human Interleukin‐2 by the Reverse Polarity Protection Strategy

The chemical synthesis of human interleukin‐2 (IL‐2) , having a core 1 sugar, by a ligation method is reported. Although IL‐2 is a globular glycoprotein, its C‐terminal region, in particular (99‐133), is extremely insoluble when synthesized by solid‐phase method. To overcome this problem, the side‐chain carboxylic acid of the Glu residues was protected by a picolyl ester, thus reversing its polarity from negative to positive. This reverse polarity protection significantly increased the isoelectric point of the peptide segment and made it positive under acidic conditions and facilitated the purification. An efficient method to prepare the prolyl peptide thioester required for the synthesis of the (28‐65) segment was also developed. These efforts resulted in the total synthesis of the glycosylated IL‐2 having full biological activity.     

Highly Fluorescent Flavins: Rational Molecular Design for Quenching Protection Based on Repulsive and Attractive Control of Molecular Alignment

Unprecedented intense fluorescent emission was observed for a variety of flavin compounds bearing a perpendicular cyclic imide moiety at the C7 position of an isoalloxazine platform. A series of alloxan‐substituted flavins was prepared selectively by reduction of the corresponding N‐aryl‐2‐nitro‐5‐alkoxyanilines with zinc dust and subsequent reaction with alloxan monohydrate in the presence of boric acid. Analogues bearing oxazolidine‐2,4‐dione functionality were obtained on methylation of the alloxan‐substituted flavins with methyl iodide and subsequent rearrangement in the presence of an inorganic base. The flavin compounds exhibit intense white‐green fluorescent emission in the solution state under UV excitation at 298 K, with emission efficiencies Φ_{298 K} greater than 0.55 in CH₃CN, which are higher than the values for all reported flavin compounds under similar conditions. The highest Φ_{298 K} value of 0.70 was obtained in CH₃CN for isoalloxazine bearing C7‐alloxan and N10‐2,6‐diisopropylphenyl groups. The temperature dependence of the emission intensities indicates that the pronounced emission properties at 298 K are attributable to the highly heat resistant properties towards emission decay with increasing temperature. Mechanistic studies, including X‐ray diffraction analysis, revealed that the good emission properties and high heat resistance of the alloxan‐substituted flavins are due to a synergetic effect of the associative nature of the C7‐alloxan unit and the repulsive nature of the perpendicular bulky substituents at the C7 and N10 positions.     

Binary and ternary complexes involving manganese(II), 2,2’-bipyridine and halide or thiocyanate ions inN,N-dimethylformamide

Ternary complexation involving the manganese(II) ion, 2,2’-bipyridine (bipy), and halide (chloride, bromide) or pseudohalide (thiocyanate) ions has been studied by precise titration calorimetry inN,N -dimethylformamide (DMF) at 298K. All the titration curves are explained well in terms of formation of mononuclear complexes of the type [MnX_m(bipy)_n](^2-m) + (X = CI, Br or SCN), and the formation of [MnCl(bipy)]⁺, [MnCl₂(bipy)], [MnCl(bipy)₂]⁺ and [MnCl₂(bipy)₂] has been established in the chloride system, [MnBr(bipy)]⁺, [MnBr₂(bipy)], [MnBr(bipy)₂]⁺ in the bromide system, and [Mn(NCS)(bipy)]⁺, [Mn(NCS)₂(bipy)], [Mn(NCS)₃(bipy)]^-, [Mn(NCS)(bipy)₂]⁺, and [Mn(NCS)₂(bipy)₂] in the thiocyanate system. The data were analyzed on the basis of the thermodynamic parameters for the binary Mn^lIbipy and Mn^II-X (X = Cl, Br and SCN) systems, the latter being determined in previous work. The formation constants, reaction enthalpies, and entropies of the ternary complexes were extracted. The thermodynamic parameters thus obtained are discussed in comparison with those of the corresponding systems of other transition metal(II) ions.     

Hanasanagin: a new antioxidative pseudo-di-peptide, 3,4-diguanidinobutanoyl-DOPA, from the mushroom, Isaria japonica

The ‘Hanasanagitake’ mushroom, Isaria japonica, is a folk medicine and a traditional health food. Fractionation of the 60% ethanol extract of the mushroom, guided by the antioxidant activity test, led to the isolation of a new pseudo-di-peptide, and it was called ‘hanasanagin’. Spectral analysis and chemical transformation determined the structure of hanasanagin as 3,4-diguanidinobutanoyl-DOPA.     

Aerobic ruthenium-catalyzed oxidative cyanation of tertiary amines with sodium cyanide

RuCl3-catalyzed oxidative cyanation of tertiary amines with sodium cyanide under molecular oxygen (1 atm) at 60 degrees C gives the corresponding alpha-aminonitriles, which are versatile synthetic intermediates of various compounds such as amino acids and unsymmetrical 1,2-diamines, in excellent yields. This reaction is clean and should be an environmentally benign and useful process.     

Explorations into new reaction chemistry

This Review describes the basic concepts that have guided our exploration of new chemical reactions by giving examples of results from my research group. Our strategy of carrying out research is to investigate three to four different topics at a time so we can gather as many results as possible. These may at first appear unrelated to each other but may have the potential to be united into a greater hypothesis after repeated feedback. Three scenarios from our research are presented: the "oxidative-reductive condensation reaction" devised in 1960, which after an interval of nearly 40 years brought forth the new concept of using compounds of structure Ph(2)POR as reducing reagents; the "TiCl(4)-aldol reaction" of 1973 that eventually led to the present "base-promoted aldol reaction" through a chain of ideas; and the "glycosylation reaction using fluorosugars" from 1984 which recently bloomed into "stereocontrolled glycosylation". Thus, it can be said that by reviewing what we had done before, we were able to expand on it to achieve new outcomes.     

Crossing the phantom divide in extended Dvali–Gabadadze–Porrati gravity

We propose a phantom crossing Dvali–Gabadadze–Porrati (DGP) model. In our model, the effective equation of state of the DGP gravity crosses the phantom divide line. We demonstrate crossing of the phantom divide does not occur within the framework of the original DGP model or the DGP model developed by Dvali and Turner. By extending their model, we construct a model that realizes crossing of the phantom divide. We find that the smaller the value of the new introduced parameter β is, the older epoch crossing of the phantom divide occurs in. Our model can account for late-time acceleration of the universe without dark energy. We investigate and show the property of Phantom crossing DGP model.