Constituting of a new surface‐initiating system on polymeric microspheres and preparation of basic protein surface‐imprinted material in aqueous solution

In this work, a new surface‐initiating system was constituted on the surfaces of cross‐linked polyvinyl alcohol (CPVA) microspheres, and on this basis, papain surface‐imprinted material was successfully prepared in aqueous solution. CPVA microspheres were modified with chlorethamin as reagent, and so a mass of primary amino group was introduced onto CPVA microspheres. Whereupon, a surface initiating system (−NH₂/S₂O₈²⁻) was formed at the interface between the microspheres and aqueous solution, in which papain as template protein, 4‐styrene sulfonate (SSS) as functional monomer, N,N′‐methylenebisacrylamide (MBA) as cross‐linker and (NH₄)₂S₂O₈ as initiator were all dissolved. In neutral solution, the polypeptide chains of papain as a basic protein were positively charged, and the molecules of anionic monomer SSS would spontaneously gather around papain polypeptide chain, forming complex by right of strong electrostatic interaction. The free radicals produced on CPVA microspheres initiated the monomer SSS around papain polypeptide chain and the cross‐linker MBA to produce graft/cross‐linking polymerization, and at the same time, papain macromolecules were embed in the cross‐linked networks. As a result, the graft/cross‐linking polymerizing of SSS and the molecule imprinting of papain were synchronously carried out, and papain surface‐imprinted material, MIP‐PSSS/CPVA microspheres, was obtained. The experimental results show that the papain surface‐imprinted material has excellent binding affinity and high recognition selectivity for papain. The binding capacity of MIP‐PSSS/CPVA microspheres for papain reaches 44 mg/g, and relative to another basic protein, trypsin (TRY) as contrast protein, the selectivity coefficient of MIP‐PSSS/CPVA microspheres for papain is 14.35, displaying very high recognition specificity.     

Cobalt(III) complexes of 2-oximino-10-oximino-3,9-dimethyl-4,8-diazaundeca-3,8-diene

Summary The pseudo-macrocyclic dioxime ligand [(1) = LH] has been synthesized. A variety of cobalt(III) complexes, trans-[CoLX₂], have been prepared and characterized (X = Cl, Br, NO₂, NCS or N₃) and [CoLCl(NO₂)]. Vis. and i.r. spectra of the complexes are reported and aspects of the solution chemistry of the complexes studied.     

Spectroscopic studies on three mixed-ligand copper(II) complexes

The mixed-ligand complexes [Cu(den)en](ClO₄)₂, [Cu(den)Pn](ClO₄)₂ and [Cu(den)tn](ClO₄)₂ (where den = diethylenetriamine, en = ethylenediamine, Pn = 1,2-diaminopropane, and tn = 1,3-diaminopropane) have been synthesized, and their IR, electronic and ESR spectral properties have been studied to understand the stereochemistry of these complexes both in the solid state and in DMF (dimethylformamide) or pyridine solutions. The metal appears to be five-coordinate in the solid state, formed with five nitrogens of the mixed ligand, and is found to change in solution, probably due to the attachment of a solvent molecule in the sixth coordination position. The equatorial and axial bond strengths are estimated in the solutions.     

Reactions of phenyllithium with lithium aluminum hydride in diethyl ether

Reactions of phenyllithium with LiAlH₄ in diethyl ether have been studied in detail. Lithium hydride, as an insoluble solid, and LiAlPh_n H_4?n (where n = 2 or 3)_in solution, are formed when the PhLi to LiAlH₄ ratio is 2/1and 3/1. However, Li₃AlH₆ is formed when LiAlH₄ is added to an equimolar solution of PhLi in diethyl ether. The integrity of the products have been established by IR, NMR and X-ray powder diffraction pattern.     

Equilibrium constants of HF,F-, HF-2 and H2F2 species in formic acid.

Equilibrium constants for the fluorinated species HF, F^-, HF^-₂ and H₂F₂ in formic acid and in a 1M potassium formate solution in formic acid have been studied by ¹⁹F NMR. The chemical shifts of these species have been determined from measurements of the shifts for various initial mixtures of differing concentrations of dissolved HF, F^- and HF^-₂. From these values, relative concentrations of HF, F^-, and HF^-₂ and H₂F₂ in each solution have been calculated through a numerical method. The following constants were obtained: K₁ = [H⁺][F^-]/[HF] = 1.1 x 10^-5M; K_D = [HF][F^-]/[HF^-₂] = 0.5 M; K′₁ = [H⁺][HF^-₂]/[H₂F₂]= 1.1 x 10^-5 M; K′_D = [HF]²/[H₂F₂]=0.5 M.     

The infrared carbonyl band of ethyl haloacetates and rotational isomerism

The integrated intensities of the carbonyl band components of the following ethyl haloacetates, R-COOFt (R = CH₂Cl, CH₂Br, CHCl₂ and CHBr₂), have been measured at different temperatures. From these intensities, values of ΔH° for the equilibrium between the $\text{cis}$ and $\text{gauche}$ rotamers have been estimated. Ethyl haloacetates have been studied in both CCl₄ solution and in gas phase. The absolute values of ΔH° in solution are lower than in gas phase. Results obtained in gas phase indicate that the stability of the $\text{gauche}$ rotamer increases with the size of the halogen atom.     

Studies on enzymic peptide synthesis: I. Synthesis of tryptophane analogue of Leu-enkephalin

A tryptophane analogue of Leu-enkephalin, Tyr-Gly-Gly-Trp-Leu-NH₂, was synthesized by stepwise elongation from C-terminal Leucylamide towards the N-terminal tyrosine using α-chymotrypsin and papain catalysis. The selections of appropriate enzymes and suitable solvents were studied. It was found that an N-blocked amino acid ester served better as a donor than the corresponding free amino acid in the peptide formation, irrespective of whether α-chymotrypsin or papain was used, while, on the other hand, an N-blocked amino acid was needed as the donor in case of thermolysin. In the last step of pentapeptide synthesis catalyzed by α-chymotrypsin, the phase transfer process seems to be preferable to the homogeneous solution method. The results of this work showed some advantages by the use of an immobilized enzyme. The tryptophane analogue of Leu-enkephalin was also synthesized by the conventional organic method. Preliminary in vitro bioassay indicated that the synthetic Try-Gly-Gly-Try-Leu-NH₂ can inhibit the contraction of the guinea Pig's ileum caused by electric stimulation to nearly the same extent as the natural Leu-enkephalin does.     

Kinetic Relationships between Reactions in the Gas Phase and in Solution

Some recent examples of reactions proceeding both in the gas phase and in solution have been investigated to determine their kinetics and mechanisms. The ratio of the corresponding rate constants, k_G and k_L, of the elementary processes studied has been found to be about unity for unimolecular reactions and between 1 and 10 for bimolecular reactions. The mechanisms, overall rates, rate constants, and activation energies have been determined for the homogeneous gas reaction NOCl + Cl₂O = NO₂Cl + Cl₂ and the reaction NOCl + N₂O₅ = NO₂Cl + 2 NO₂, carried out in C₂F₃Cl₃.     

Nanoparticles based on gadolinium(iii) and europium(iii) complexes for biovisualization

Complexes Ln(TTA)₃ and [Ln(TTA)₃·1] (Ln = Eu, Gd; ТТА is thenoyltrifluoroacetyl-acetonate; 1 is 2-(5-chlorophenylene-2-hydroxy)-2-phenylethylene-bis(2-methoxy)phosphine oxide) in individual form, and as a part of a core of the polyelectrolyte stabilized colloids have been studied by Mössbauer spectroscopy and X-ray powder diffraction. The photophysical and colloidal characteristics of the solutions of polyelectrolyte nanoparticles were studied in water, artificial cerebrospinal fluid solution, solution of bovine serum albumin, and human blood serum. A stability of a luminescent response of the nanoparticles in solutions of bovine serum albumin and human blood serum at 37 °С for 2 hours has been revealed. This is a prerequisite for the potential application of studied nanoparticles for biovisualization.

     

粉状白钨酸的研究——ⅩⅫ.六聚钨酸二甲基亚砜加合物的制备

1968年,Fuchs等首次用控制水解法从WO(CH_3)_4中获得了六聚钨酸盐,它的阴离子W_6O_(19)~(2-)结构也已被测定。迄今六钨酸盐主要还是局限于几个多碳有机胺盐。以粉状白钨酸为原料,在二甲基亚砜(DMSO)中制得了一系列DMSO配位的多价金属的六钨酸盐晶体,并测定了其中部分盐类的晶体结构。但六聚钨酸仍未     

Preparation, crystal structures and oxidation activity of two novel nickel(II) complexes of tripodal ligand containing coordinated solvent molecules

Two novel Ni^II complexes, [Ni(TMPzA)(CH₃CN)(H₂O)]· (ClO₄)₂ (1) and [Ni(TMPzA)(CH₃OH) (NCS)]· (ClO₄) (2), where TMPzA = tris[(3,5-dimethyl-1-pyrazolemethyl)amine], have been synthesized and characterized. Their crystal structures were determined by X-ray diffraction analysis. Both complexes were isolated from the reactions of TMPzA ligand with metal salts, and thiocyanate as the second ligand in CH₃CN solution for (1) and in CH₃OH solution for (2), respectively. The title complexes are mononuclear structures, and which further assembled into a dimer by the intermolecular hydrogen bond in the unit cell, respectively. The solvent molecules participate in coordination. The spectra properties of the two complexes in solution have been further studied and discussed. The oxidation of styrene catalyzed by the title complexes has been studied, and the new complexes show some catalytic activity under the reaction conditions.     

One - determinantal pure state versus ensemble Kohn-Sham solutions in the case of strong electron correlation: CH2 and C2

The possibility that the Kohn-Sham (KS) solution for a noninteracting auxiliary electron system is not the conventional one-determinantal pure state but a few-determinantal ensemble has been investigated. The KS solutions (the exchange-correlation potential v _xc and the orbitals) have not been approximated by local-density or density-gradient approximations but have been constructed from an accurate ab initio electron density. The lowest singlet states of the CH₂ and C₂ molecules have been selected for this investigation since for these cases the ground-state wave function Ψ is nondegenerate but has an essentially multideterminantal character (electron correlation is strong). For C₂ the dependence of the type of KS solution on the bond distance R(C–C) has been studied at the QZ level. For the shortest distance considered, R(C–C)=1.8 a.u., a pure-state KS solution has been obtained. For the equilibrium distance R _e(C–C)=2.348 a.u. and at larger distances ensemble solutions have been obtained with widely varying weights of the individual determinants, depending on the bond distance. For CH₂ the dependence of the type of KS solution on the basis has been studied: calculation in the triple zeta (TZ) basis for the KS orbitals yields an ensemble solution, while the pure-state KS solution has been obtained in the quadruple zeta (QZ) basis. The form of the KS orbitals has been compared with that of the natural orbitals (NOs). It has been shown for the model example of the stretched H₂ molecule as well as for CH₂ and C₂, that the KS orbitals of the pure state may be rather different from the corresponding NOs, while the occupied KS orbitals of the ensemble solution can be considered as plausible approximations to the corresponding NOs. Received: 10 February 1998 / Accepted: 10 June 1998 / Published online: 3 September 1998     

Studies on ruthenium(III) chalcone thiosemicarbazone complexes as catalysts for carbon–carbon coupling

New six-coordinate ruthenium(III) complexes [RuX(EPh₃)₂(L)] (X = Cl or Br; E = P or As; L = chalcone thiosemicarbazone) have been prepared by reacting [RuX₃(EPh₃)₃] (X = Cl or Br; E = P or As) with chalcone thiosemicarbazones in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (IR, electronic, mass, and EPR) data. The redox behavior of the complexes has also been studied. Based on the above data, an octahedral structure has been assigned for all the complexes. The new complexes exhibit catalytic activity for carbon–carbon coupling reactions.     

Spectroscopic,NMR and PMR studies on monoadducts of cobalt(II) and nickel(II) diaryldithiophosphinates with oxygen donor ligands

The high-spin CoS₄O core is stabilized in monoadducts of composition Co(X)₂(L), (X = diphenyldithiophosphinate or its p-tolyl analogue; L = pyridine N-oxide, γ-picoline N-oxide, dimethylformamide and dimethylsulfoxide). A pentacoordinate stereochemistry has been assigned on the basis of spectral and magnetic properties. Assignments of some IR frequencies in the region 4000-400 cm⁻¹ have been made. The corresponding addition complexes of planar Ni(X)₂ were studied spectroscopically in solution and the occurrence of ligand field bands around 13,500 and 21,000 cm⁻¹ in solutions containing amine-oxide is due to the formation of monoadducts Ni(X)₂(L). The contact shifts observed for the protons of the amine-oxides in these complexes have been studied to understand the spin-transfer mechanism. The results indicate that a π-mechanism is operative and comparison of the experimental data with the theoretically calculated spin densities (INDO approach) suggest that the HBO (Highest Bonding Orbital) is involved in the spin transfer mechanism. The shift pattern for the Co(X)₂(L) is influenced by a dipolar contribution and we conclude that the shifts are the net result of π-delocalization and negative dipolar contribution.     

MONO-ORGANOMERCURY AND DIORGANOTHALLIUM DERIVATIVES OF THIOHYDANTOIN AND 5-(BENZYLIDENE)-2-THIOHYDANTOIN: THE CRYSTAL STRUCTURE OF DIMETHYL-[5-(BENZYLIDENE)-2-THIOHYDANTOINATO]-THALLIUM(III)

Abstract

The complexes [TlR₂(Td)], [TlR₂(BTd)], [HgR(Td)] and [HgR(BTd)] (R = Me, Ph; HTd = thiohydantoin; HBTd = 5-(benzylidene)-2-thiohydantoin) were prepared by reacting the appropriate ligand with the appropriate diorganothallium hydroxide or mono-organomercury acetate. They have been studied in the solid state (by vibrational spectroscopy and mass spectrometry) and in solution (by using NMR). In addition, the crystal structure of [TlMe₂(BTd)] has been determined by X-ray diffraction. The crystals have a polymeric structure in which each thallium atom is coordinated to the two methyl C atoms, the S and N atoms of one BTd ligand. the S atom of another and the O atom of a third. The coordination modes of the two ligands in the other complexes are discussed on this basis in the light of spectroscopic data.     

Arenetitatnium(II) complexes of formula Ar-TiCl2-Al2Cl6

The synthesis and properties of Ar-TiCl₂-Al₂Cl₆(Ar=benzene or a methylbenzene) complexes have been studied, and the results indicate an increase in stability of the arenetitanium π-bond in the order: benzene < toluene < xylenes < mesitylene < durene < hexamethylbenzene.An exchange reaction of the aromatic ligands was observed. On the basis of conductivity measurements it was ascertained that the complexes are partialy ionize in solution.     

The structure of the charge transfer complex in olefin quenching of benzophenone phosphorescence

The phosphorescence lifetimes of ω-alkenyl esters of p-benzophenone-carboxylic acid have been measured in dilute solution in degassed acetic acid solution. The lifetimes were extrapolated to infinite dilution. Intramolecular quenching was not very significant in benzophenone-4-CO₂(CH₂)_nCHCH₂ for n = 1, 2 or 4. For n = 9 the phosphorescence lifetime was found to be 2 μs compared to 70 μs for n = 1, 2. These results are interpreted to mean that the quenching complex has a specific geometric requirement with the CHCH₂ group approaching within a van der Waals distance of the ketone carbonyl group.     

Preparation and degradation of copolymers of methyl methacrylate with alkali metal methacrylates—I. Copolymerization parameters for the systems methyl methacrylate-lithium methacrylate,methyl methacrylate-sodium methacrylate and methyl methacrylate-potassium methacrylate

Copolymerizations of methyl methacrylate with the Li, Na and K salts of methacrylic acid have been studied in methanol solution at 60°. Reactivity ratios have been calculated by the methods due to Mayo and Lewis, Fineman and Ross and Peckham. The rate of copolymerization decreases as the size of the metal cation increases, in contrast to the behaviour in the homopolymerization of the alkali metal methacrylates. The systems have the following reactivity ratios (MMA as monomer-1): Li salt r₁ = 0.59, r₂ = 0.073; Na salt r₁ = 3.97, r₂ = 0·126; K salt r₁ = 5.65, r₂ = 0.143. The MMA-LiMA system shows azeotropic copolymerization for a mole fraction of MMA in the feed equal to 0.7. This system shows a strong tendency towards alternation (r₁r₂ = 0.044). The differences in the reactivity ratios are discussed in relation to steric and electrostatic effects.     

Etude thermochimique de carboxylates de cuivresolvates par des amines aromatiques

The carboxylates (formate, acetate, propionate, isobutyrate) of copper(II) solvated by aromatic amines (pyridine; α, β and γ picolines) corresponding to the formula Cu(R?COO)₂(H₂O)_x(Am)_y(x = 0,1 or 2, and γ = 1 or 2) have been prepared. The thermal decomposition has been studied by TG and DTA methods. The standard enthalpies of formation have been determined and a relation has been proposed for the estimation of these values.     

Fluorination of Hydrogen-containing with elemental fluorine

The hydrohalo-olefins cis and trans CHC1=CHC1, CHC1=CC1₂, CHC1=CH-CH₂C1 and CH₂=CC1-CH₂C1 have been fluorinated with elemental fluorine to give good yields of hydrohalofluoroalkanes. The best operational conditions for F₂ addition to the double bond rather than hydrogen and/or chlorine atom substitution, dimerization and oligomerization of radical intermediates have been studied. Preliminary studies on the reaction of Freon 12 and Freon 22 towards elemental fluorine have also been carried out.