Synthesis and structure of 1-zirconacyclopent-3-yne complexes without substituents adjacent to the triple bond

Five-membered metallacyclic alkynes that have no substituents adjacent to the triple bond have been synthesized, isolated, and structurally characterized. Zirconocene dichlorides, Cp'2ZrCl2 (Cp' = C5H5, C5H4-t-Bu), reacted with 1,4-dichlorobut-2-yne in the presence of magnesium to give 1-zirconacyclopent-3-yne compounds (5 (a) Cp' = C5H5, (b) Cp' = C5H4-t-Bu) that have a -CH2CCCH2- moiety in good yields. They are stable enough to be isolated in a pure form, despite the absence of substituents. 5a reacted with an equimolar amount of Cp2Zr(but-1-ene)(PMe3) to produce a bimetallic complex in which the zirconacyclopentyne coordinates to the other zirconocene moiety as an alkyne.     

Large volume preconcentration and purification for determining the240Pu/<Superscript>239</Superscript>Pu isotopic ratio and <Superscript>238</Superscript>Pu/<Superscript>239+240</Superscript>Pu alpha-activity ratio in seawater

Summary The present paper describes a new analytical method for determining the ²⁴⁰Pu/²³⁹Pu isotopic ratio and ²³⁸Pu/^239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO₂-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV) using NaNO₂, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO₂. The ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry, respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering ²³⁸U (3.3 μg^. l^-1in seawater) was effectively removed with a decontamination factor of 1.7·10⁷. The accuracy of the method for the ²⁴⁰Pu/²³⁹Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied to the determination of the ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in coastal and oceanic water.     

Basic peptides as functional components of non-viral gene transfer vehicles

Improving the performance of non-viral gene-delivery vehicles that consist of synthetic compounds and nucleic acids is a key to successful gene therapy. Supplementing synthetic vehicles with various biological functions by using natural or artificial peptides is a promising approach with which to achieve this goal. One of the obstacles hindering this effort is that some of the potentially useful peptides, especially those with many basic amino acid residues, interfere with the formation of the complex owing to strong electrostatic interactions with the nucleic acid. In this review, we describe our recent work in examining the potential of these peptides in gene delivery, using a recombinant lambda phage particle as the model for the gene-delivery complex. Lambda phage encapsulates large duplex DNA in a rigid polyplex-like shell with a diameter of 55 nm, and can display various peptides on this capsid, independently of particle formation. By examining the expression of marker genes encapsulated in the phage capsid, we have demonstrated that the protein transduction domain of HIV Tat protein and the nuclear localization signal derived from SV40 T antigen can remarkably facilitate the delivery of these marker genes across the two major barriers, the cell membrane and the nuclear membrane, respectively. Our results indicate that these basic peptides can constitute effective components of synthetic gene-transfer complexes, as long as sufficient copies are displayed on the outer surface of the complex.     

Adduct formation properties of mono- and bidentate phosphine oxide compounds in the liquid—liquid extraction of some divalent metals with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone

The bidentate phosphine oxide compounds bis(diphenylphosphinyl)methane (BDPPM) and bis(diphenylphosphinyl)ethane (BDPPE) were synthesized and the liquid—liquid extraction equilibria of some divalent metal ions such as Co(II), Ni(II), Zn(II) and Cd(II) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) and the neutral phosphine oxide compounds were investigated. BDPPM was found to be much more powerful than BDPPE and the monodentate neutral ligand trioctylphosphine oxide (TOPO). The composition of the extracted species were determined by a graphical method to be M(PMBP)₂(TOPO)_s (s = 2 for Co, Ni, Cd and s = 1 for Zn), M(PMBP)₂(BDPPM) and M(PMBP)₂(BDPPE). The adduct formation constants between the acylpyrazolone chelates and the neutral ligands were determined and are discussed in terms of the molecular structure.     

Penning ionization electron spectroscopy of C6H6 by collision with He*(2 3 S) metastable atoms and classical trajectory calculations: optimization of ab initio model potentials

The potential energy surface of benzene (C(6)H(6)) with a He*(2(3)S) atom was obtained by comparison of experimental data in collision-energy-resolved two-dimensional Penning ionization electron spectroscopy with classical trajectory calculations. The ab initio model interaction potentials for C(6)H(6)+He*(2(3)S) were successfully optimized by the overlap expansion method; the model potentials were effectively modified by correction terms proportional to the overlap integrals between orbitals of the interacting system, C(6)H(6) and He*(2(3)S). Classical trajectory calculations with optimized potentials gave excellent agreement with the observed collision-energy dependence of partial ionization cross sections. Important contributions to corrections were found to be due to interactions between unoccupied molecular orbitals and the He*2s orbital. A C(6)H(6) molecule attracts a He*(2(3)S) atom widely at the region where pi electrons distribute, and the interaction of -80 meV (ca. -1.8 kcal/mol) just cover the carbon hexagon. The binding energy of a C(6)H(6) molecule and a He* atom was 107 meV at a distance of 2.40 A on the sixfold axis from the center of a C(6)H(6) molecule, which is similar to that of C(6)H(6)+Li and is much larger than those of the C(6)H(6)+[He,Ne,Ar] systems.     

Crystal engineering of photochromic diarylethene single crystals

Photochromic performance of diarylethene single crystals was controlled by crystal engineering using non-covalent aromatic-aromatic interactions as the directional intermolecular force. A diarylethene derivative with two pentafluorophenyl groups, 1,2-bis(2-methyl-5-pentafluorophenyl-3-thienyl)perfluorocyclopentene (1a), formed stoichiometric co-crystals with benzene (Bz) and naphthalene (Np) by aryl-perfluoroaryl interactions. Face-to-face pi-stacking interactions between the pentafluorophenyl groups of 1a and the aromatic molecules are responsible for 2:1 and 1:1 stoichiometric compositions in 1a/Bz and 1a/Np co-crystals, respectively. The diarylethene underwent thermally stable and photoreversible photochromic reactions in a homo-crystal of 1a and co-crystals 1a/Bz and 1a/Np. The absorption spectra of the photogenerated closed-ring isomers varied depending on the conformation of the diarylethene molecules packed in the crystals. The diarylethene 1a also formed 1:1 stoichiometric co-crystals with different kinds of diarylethenes, 1,2-bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (2a) and 1,2-bis[2-methyl-5-(1-naphthyl)-3-thienyl]perfluorocyclopentene (3a). Both co-crystals 1a/2a and 1a/3a showed photochromism. Although 1a, 2a, and 3a underwent efficient photocyclization reactions in their homo-crystals, highly selective photocyclization reactions of 2a or 3a were observed in the co-crystals. The selective reactions were confirmed by HPLC and X-ray crystallography. Excited energy transfers from 1a to 2a and from 1a to 3a are considered to occur and cause the selective reactions.     

A unification of the existence theorems of the nonlinear complementarity problem

The nonlinear complementarity problem is the problem of finding a point x in the n-dimensional Euclidean space,R ⁿ , such that x ? 0, f(x) ? 0 and 〈x,f(x)～ = 0, where f is a nonlinear continuous function fromR ⁿ into itself. Many existence theorems for the problem have been established in various ways. The aim of the present paper is to treat them in a unified manner. Eaves's basic theorem of complementarity is generalized, and the generalized theorem is used as a unified framework for several typical existence theorems.     

Permutation Cellular Automata

Permutation cellular automata are cellular automata defined by using finite maximal prefix codes. The overall dynamics of onesided and twosided permutation cellular automata is studied. For some classes of permutation cellular automata including the class of those defined by using finite maximal bifix codes, the overall dynamics is completely or partially described in terms of the codes used to define them.