Alternative molecularly imprinted polymeric membranes from a tetrapeptide residue consisting of D- or L-amino acids

Alternative molecularly imprinted polymeric membranes were prepared from a polystyrene resin bearing tetrapeptides consisting of D -amino acids or L-amino acids. The membrane prepared from a DLDE derivative (H-Asp(OcHex)-Leu-Asp(OcHex)-Glu(OBzl) CH₂ ) consisting of D -amino acids and imprinted by Boc-D -Trp recognizes the D-isomer in preference to the corresponding L -isomer and vice versa. The amino acid preferentially adsorbed by the membrane was selectively permeated by applying electrodialysis.     

Observation of internal-conversion electrons induced by inelastic nuclear resonant scattering

Measurements of the internal-conversion electron emission due to the inelastic nuclear resonant excitation are reported. thin films of 20 and 1.3 nm thickness were deposited on Si(1 1 1), and the internal-conversion electrons were measured as a function of the photon energy. From the inelastic part of the spectra, the phonon density of states was obtained. Whereas the phonon density of states of 20-nm thick film resembles that of bulk -Fe, the 1.3-nm thick film revealed an obvious softening of the acoustic mode.     

Synthesis of donor-acceptor chromophores by the [2 + 2] cycloaddition of arylethynyl-2H-cyclohepta[b]furan-2-ones with 7,7,8,8-tetracyanoquinodimethane

Arylethynyl-2H-cyclohepta[b]furan-2-ones reacted with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2 + 2] cycloaddition reaction, followed by ring opening of the initially formed cyclobutene derivatives, to afford the corresponding dicyanoquinodimethane (DCNQ) chromophores in excellent yields. The intramolecular charge-transfer (ICT) interactions between the 2H-cyclohepta[b]furan-2-one ring and DCNQ acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel DCNQ derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties depended on the number of DCNQ units in the molecule. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.     

A synchrotron X‐ray study of triclinic LiCa2Nb3O10 with perovskite‐type slabs

The triclinic superstructure of a small crystal of LiCa₂Nb₃O₁₀, lithium dicalcium triniobium decaoxide, has been investigated by synchrotron X‐ray diffraction. The unit cell is an almost rectangular parallelepiped, although there is a 0.245° offset from orthogonality for β. The structure essentially belongs to a homologous series of Li[Na_n?3Ca₂Nb_nO_3n+1] with n = 3, where the moiety in square brackets has a perovskite‐type slab structure. The superstructure has a doubled unit‐cell volume with respect to the tetragonal aristotype. The NbO₆ octahedra are rotated about axes parallel to [110] by approximately 10°. Adjacent slabs are connected by Li atoms and are geo­metrically related by 4₂ pseudosymmetry lying parallel to c . There are twice as many sites as Li atoms, providing a variation of population at these Li sites.     

Molecular Transformation to Pyrroles,Pentafulvenes, and Pyrrolopyridines by [2+2] Cycloaddition of Propargylamines with Tetracyanoethylene

In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines.     

Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.     

Preparation, characterization, and cycloaddition reaction of the heterocumulenes attached directly to azulenes. An efficient strategy for the preparation of azulene-substituted heterocycles

Preparation and cycloaddition reaction of novel azulene-substituted N-sulfinylamines 1 and 2 are reported. The influence of the -NSO group on the UV-vis and NMR spectra of the azulene ring to which it is bonded is discussed. X-ray crystal analysis of 1 revealed the syn-configuration and the twisted structure of the N-sulfinylamine moiety. The synthetic utility of 1 and 2 have been explored by the cycloaddition reaction to afford novel azulene-substituted heterocycles under high-pressure conditions. We also described herein the synthesis and some properties of related 2-azulenylisothiocyanate.     

Efficient preparation of 2-azulenylboronate and Miyaura-Suzuki cross-coupling reaction with aryl bromides for easy access to poly(2-azulenyl)benzenes

This paper describes an efficient preparation of 2-azulenylboronate (6) starting from 2-iodoazulene by halogen-metal exchange reaction using n-BuLi and subsequent quenching with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. The boronate 6 has been found to undergo Pd-catalyzed Miyaura-Suzuki cross-coupling reaction with a range of aryl bromides including aromatic poly bromides utilizing Pd₂(dba)₃-P(t-Bu)₃ as a catalyst and establishes a strategy to produce novel poly(2-azulenyl)benzenes, some of which are found to be insoluble in common organic solvents, however. The redox behavior of 2-arylazulenes and poly(2-azulenyl)benzenes was examined by cyclic voltammetry (CV) and compared with those of 6-azulenylbenzene derivatives reported previously.     

A method to circumvent the lot number of activated carbon affecting the performance of activated carbon silica gel columns used for cleanup of blood samples for analysis of 29 hazardous organochlorine compounds

We have previously described the use of a tandem simplified multilayer silica gel-activated carbon dispersed silica gel (TS-ML-AC) column for the cleanup of blood samples for the analysis of 29 hazardous organochlorine compounds (OCs)--the 17 major polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) and 4 non-ortho- and 8 mono-ortho-polychlorinated biphenyls (PCBs). We noted that the performance of the activated carbon-silica gel (ACS) column (lower column) varied with the lot number of the ACS. In this study, we compared the elution profiles of OCs eluted on 5 ACS columns, each with a different ACS lot number, and found that only mono-ortho-PCBs #114 and #123 were affected by lot number. The problem was that the 50 ml of n-hexane required to elute all the OCs from the simplified multilayer silica gel (MLS) column (upper column) into the AC column (lower column) also eluted varying amounts of PCBs #114 and #123 from the ACS column by ACS lot number. Although we could prevent PCBs #114 and #123 from being eluted from the ACS column by reducing the n-hexane volume to 10 ml, this volume was not sufficient to elute all the OCs from the MLS column. We solved this by separating the two columns; the sample solution was eluted with 50 ml of n-hexane from the MLS column, this eluate was concentrated to about 0.3 ml using a rotary evaporator, and then the concentrated solution was cleaned up on the ACS column. The recovery rates of #114 and #123 from blood samples were above 70% and the relative standard deviations of their concentration were below 10%, irrespective of the lot number, compared with recovery rates of 45-79% for #114 and 59-89% for #123, and relative standard deviations of their concentration above 15% when 50 ml of n-hexane was run through the tandem column. Our modified method affords reliable and reproducible cleanup of blood samples for analysis of 29 OCs, irrespective of the ACS lot number.     

Poly(amine ester) dendrimer with naphthyl units as a fluorescent chemosensor for Al(III), Cu(II), and Zn(II).

A poly(amine ester) dendrimer with naphthyl units (G1N6) has been synthesized as a fluorescent chemosensor for metal ions. We investigated the metal-ion recognition of G1N6 by adding each of Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Ni(2+), and Zn(2+) in acetonitrile solution. Large changes were observed in the fluorescence spectra of G1N6 upon the addition of Al(3+), Cu(2+), and Zn(2+).