A novel inhibitor for Fe-type nitrile hydratase: 2-cyano-2-propyl hydroperoxide

Nitrile hydratase (NHase) is a non-heme iron or non-corrin cobalt enzyme having two post-translationally modified ligand residues, cysteine-sulfinic acid (alphaCys112-SO(2)H) and -sulfenic acid (alphaCys114-SOH). We studied the interaction between Fe-type NHase and isobutyronitrile (iso-BN) which had been reported as a competitive inhibitor with a K(i) value of 5 microM. From detailed kinetic studies of the inhibitory effect of iso-BN on Fe-type NHase, we found that authentic iso-BN was hydrated normally and that the impurity present in commercially available iso-BN inhibited NHase activity strongly. The inhibitory compound induced significant changes in the UV-vis absorption spectrum of NHase, suggesting its interaction with the iron center. This compound was purified by using reversed-phase HPLC and identified as 2-cyano-2-propyl hydroperoxide (Cpx) by (1)H and PFG-HMBC NMR spectroscopy. Upon addition of a stoichiometric amount of Cpx, NHase was irreversibly inactivated, probably by the oxidation of alphaCys114-SOH to Cys-SO(2)H. This result suggests that the -SOH structure of alphaCys114 is essential for the catalytic activity. The oxygen atom in Cys-SO(2)H is confirmed to come from the solvent H(2)O. The oxidized NHase was found to induce the UV-vis absorption spectral changes by addition of Cpx, suggesting that Cpx strongly interacted with iron(III) in the oxidized NHase to form a stable complex. Thus, Cpx functions as a novel irreversible inhibitor for NHase.     

Analysis of the π-electronic structure of infinitely large networks. I. Some remarks on the characteristic polynomial and density of states of large polycyclic aromatic hydrocarbons

General expressions of the characteristic polynomials of various series of cyclic and linear polymers of polycyclic aromatic hydrocarbons are presented, i.e., polyacene, zigzag-polyacene, 1,4-dimethylbenzene polymer, polyperylene, etc. The densities of states of cyclic and linear polymers with the same repetitive units are shown. In some cases the allowed region of the energy levels of these polymers is found not to be the same. Several related problems are discussed.     

Electrochemical synthesis of aldehydes and acetals from α-phenylthiocarboxylic acid

α-Phenylthiocarboxylic acids were converted to the corresponding aldehydes or acetals with oxidative decarboxylation and desulfurization by electrolysis.     

Extraction Chemistry of Palladium(II). Mechanism of Antagonistic Synergistic Extraction of Palladium By A 4-Aroyl Derivative of 1-phenyl-3-Methyl-Pyrazolone-5- one and Trialkylamine of High Molecular Weight

The synergistic extraction behavior of Pd^II, one of the main radioactive fission products in the reprocessing process, from HNO₃ solutions with a 4-aroyl derivative of 1-phenyl-3-methyl-pyrazolone-5-one (PMP), a weakly acidic chelating extractant 1-phenyl-3-methyl-4-(2-methoxybenzoyl)-pyrazolone-5-one (HPMMBP), and a trialkylamine of high molecular weight, tri-iso-octylamine (TiOA), has been studied. An obviously antagonistic extraction effect was observed in the extraction system under the given conditions. To understand this phenomenon, a preliminary investigation was performed to explain the mechanism of this reaction. According to the theory of the corresponding solutions (TCS), the association between HPMMBP and TiOA is presented and discussed in the organic phase. An associated species HPMMBP·TiOA formed through hydrogen bonding in a CHCl₃ medium might be the main reason why an antagonistic extraction effect occurred. The association constant between HPMMBP and TiOA was calculated to be 0.212 ± 0.03     

Thermolysis of [1,2,4]triazolo[1,5-a]pyrimidine n-ylides

5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidinio-3-phenacylide ($\text{3}$) generated by the reaction of an iminium salt ($\text{2}$) with 1 eq. of triethylamine, underwent a new thermal ring cleavage of the triazole moiety to give the pyrimidine derivative. However reaction of $\text{2}$ with 2 eq. of triethylamine afforded the 2-iminooxazoline derivative. The iminooxazoline reacted with nucleophiles such as alcohols or amines to give imidazoles.     

Multiply charged carbon ions produced from C2H2 and CH4 molecules in energetic,heavy ion impact

Multiply charged carbon ions up to C⁵⁺ ions have been observed from C₂H₂ and CH₄ molecules in 1.05 MeV/amu Ar¹²⁺ ion impact. These ions are believed to be produced through processes where multiply charged molecular ions are produced first by direct ionization and, then, dissociate via Coulomb explosion into atomic ions. The peak positions of ions from C₂H₂ molecules are found to be shifted with respect to those of ions from CH₄ molecules and this shift is understood to be due to the initial kinetic energy provided through the Coulomb potential between the dissociating ions.     

Novel synthetic approach to creating PtCo alloy nanoparticles by reduction of metal coordination nano-polymers

PtCo alloy nanoparticles with different metal elemental ratios (Pt/Co = 0.9, 1.6, 2.9, and 3.6) were prepared by a novel synthetic approach, using the transformation reaction of platinum(IV)/cobalt tetracyanoplatinate metal coordination nano-polymers (Pt(II)-CN-Pt(IV)/Co)via a H2 gas-phase reduction.     

Synthesis and Characterization of Acetylene‐Linked Bisphenalenyl and Metallic‐Like Behavior in Its Charge‐Transfer Complex

We prepared and isolated a phenalenyl‐based neutral hydrocarbon ( 1 b ) with a biradical index of 14 %, as well as its charge‐transfer (CT) complex 1 b –F₄‐TCNQ. The crystal structure and the small HOMO–LUMO gap assessed by electrochemical and optical methods support the singlet‐biradical contribution to the ground state of the neutral 1 b . This biradical character suggests that 1 b has the electronic structure of phenalenyl radicals coupled weakly through an acetylene linker, that is, some independence of the two phenalenyl moieties. The monocationic species 1 b^{. +} was obtained by reaction with the organic electron acceptor F₄‐TCNQ. The cationic species has a small disproportionation energy ΔE for the reaction 2× 1 b^{. +}? 1 b + 1 b ²⁺, which presumably originates from the independence of the phenalenyl moieties. The small ΔE led to a small on‐site Coulombic repulsion U_eff=0.61 eV in the CT complex. Moreover, a very effective orbital overlap of the phenalenyl rings between molecules afforded a relatively large transfer integral t=0.09 eV. The small U_eff/4t ratio (=1.7) resulted in a metallic‐like conductive behavior at around room temperature. Below 280 K, the CT complex showed a transition into a semiconductive state as a result of bond formation between phenalenyl and F₄‐TCNQ carbon atoms.     

Construction of hydrogen-bonded and coordination-bonded networks of cobalt(II) with pyromellitate: synthesis,structures, and magnetic properties

Synthesis (hydrothermal and metathesis), characterization (UV-vis, IR, TG/DTA), single-crystal X-ray structures, and magnetic properties of three cobalt(II)-pyromellitate complexes, purple [Co(2)(pm)](n) (1), red [Co(2)(pm)(H(2)O)(4)](n) x 2nH(2)O (2), and pink [Co(H(2)O)(6)](H(2)pm) (3) (H(4)pm = pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid)), are described. 1 consists of one-dimensional chains of edge-sharing CoO(6) octahedra that are connected into layers via O-C-O bridges. The layers are held together by the pyromellitate (pm(4-)) backbone to give a three-dimensional structure, each ligand participating in an unprecedented 12 coordination bonds (Co-O) to 10 cobalt atoms. 2 consists of a three-dimensional coordination network possessing cavities in which unbound water molecules reside. This highly symmetric network comprises eight coordinate bonds (Co-O) between oxygen atoms of pm(4-) to six trans-Co(H(2)O)(2). 3 possesses a hydrogen-bonded sandwich structure associating layers of [Co(H(2)O)(6)](2+) and planar H(2)pm(2-). The IR spectra, reflecting the different coordination modes and charges of the pyromellitate, are presented and discussed. The magnetic properties of 1 indicate complex behavior with three ground states (collinear and canted antiferromagnetism and field-induced ferromagnetism). Above the Néel temperature (T(N)) of 16 K it displays paramagnetism with short-range ferromagnetic interactions (Theta = +16.4 K, mu(eff) = 4.90 mu(B) per Co). Below T(N) a weak spontaneous magnetization is observed at 12.8 K in low applied fields (H < 100 Oe). At higher fields (H > 1000 Oe) metamagnetic behavior is observed. Two types of hysteresis loops are observed; one centered about zero field and the second about the metamagnetic critical field. The critical field and the hysteresis width increase as the temperature is lowered. The heat capacity data suggest that 1 has a 2D or 3D magnetic lattice, and the derived magnetic entropy data confirm an anisotropic s(eff) = 1/2 for the cobalt(II) ion. Magnetic susceptibility data indicate that 2 and 3 are paramagnets.     

Reaction of benzothiazoline with benzyne - generation of novel heterocyclic sulfur ylide,benzothiazolinium s-ylide

A novel heterocyclic sulfur ylide, 2-t-butyl-3-methyl-1-phenylbenzothiazolinium ylide ($\text{13}$) was generated as an intermediate in the reaction of 2-t-butyl-3-(nethy1benzothiazoline ($\text{2}$) with benzyne. The S-ylide $\text{13}$ underwent a novel intermolecular [1,2] shift to give 2-t-butyl-3-methyl-2-phenylbenzothiazoline ($\text{4}$).