Semiempirical molecular orbital calculations on boranes

Traditional Pariser-Parr-Pople and variable electronegativity calculations have been carried out on C₆H₅B(OR)₂ and p-CH₃OC₆H₄B(OR)₂, and the results compared with calculations for C₆H₅BR₂. It is concluded that the VE-SCF method offers a real advantage over the simple PPP method for predicting percent charge transfer and transition intensity in cases where excited states possess substantial C.T. character. The restriction that empirically chosen parameters fit the observed transition energies and intensities of both triarylboranes and ArB(OR)₂ requires the choice of a boron VSIP greater than 2.0 eV in the fixed parameter procedure of the usual PPP-SCF-CI method for these molecules. Observed transitions in C₆H₅B(OR)₂ correlate with ¹ L _b, ¹ L _a, ¹ B _b, whereas the first absorption maximum of (C₆H₅)₃B is assigned to C.T. (¹ A ₁¹ A ₁) local C _2v symmetry.

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Zusammenfassung PPP- und VE SCF-Rechnungen wurden für C₆H₅B(OR)₂ und p-CH₃OC₆H₄(OR)₂ durch- geführt, und die Ergebnisse wurden mit denjenigen für C₆H₅BR₂ verglichen. Es kann der Schluß gezogen werden, daß die VE SCF-Methode einen Vorteil gegenüber der einfachen PPP-Methode bietet, um den prozentualen Charge Transfer und Übergangsintensitäten in Fällen zu bestimmen, in denen die angeregten Zustände einen wesentlichen C.T.-Charakter besitzen. Die Bedingung, daß die empirisch gewählten Parameter den beobachteten Übergangsenergien und -intensitäten von sowohl Triarylboranen als auch ArB(OR)₂ angepaßt sein sollen, erfordert die Wahl eines Bor-VSIP größer als 2,0 eV im Rahmen der üblichen Parametrisierung der PPP-SCF-CI-Methode. Beobachtete Über-gänge in C₆H₅B(OR)₂ korrelieren mit ¹ L _b, ¹ L _a, ¹ B _b, wogegen das erste Absorptionsmaximum des (C₆H₅)₃B einem C.T.-Übergang (¹ A ₁¹ A ₁) lokaler C_2v -Symmetrie zugeordnet wird.

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Résumé Des calculs traditionnels Pariser-Parr-Pople et des calculs d'électronégativité variable ont été effectués sur C₆H₅B(OR)₂ et p-CH₃OC₆H₄B(OR)₂ avec comparison aux résultats obtenus pour C₆H₅BR₂. La conclusion est que la méthode VE-SCF offre un réel avantage sur la méthode PPP simple en ce qui concerne la prédiction du transfert de charge et de l'intensité de transition pour les états excités possédant un net caractère de transfert de charge. La restriction selon laquelle les paramètres empiriques doivent permettre de reproduire les énergies de transition et les intensités des deux triarylboranes et de ArB(OR)₂, nécessite le choix d'un potential d'ionisation de l'état de valence du bore supérieur de 2 eV à celui employé dans les méthodes ordinaires. Les transitions observées dans C₆H₅B(OR)₂ sont reliées à ¹ L _b, ¹ L _a, ¹ B _b, tandis que la première absorption de (C₆H₅)₃B est attribuée à un transfert de charge (¹ A ₁¹ A ₁) de symétrie locale C_2v.

     

Synthesis of a rare‐metal adsorbing polymer by three‐component polyaddition of diamines,carbon disulfide,and diacrylates in an aqueous/organic biphasic medium

Three‐component polyaddition of diamines, carbon disulfide (CS₂), and diacrylates in an aqueous/organic biphasic medium produced a polymer capable of adsorbing rare metals. By using a 1:1 mixture of toluene and H₂O, the polyaddition reaction of 1,3‐di‐4‐piperidylpropane (1), CS₂, and 1,6‐hexanediol diacrylate (2) proceeded efficiently in the presence of Et₃N to produce a poly(dithiourethane‐amine) with a high proportion of dithiourethane units almost quantitatively. Quantitative formation of 1‐CS₂ adducts in the aqueous phase was followed by efficient reaction with diacrylate at the biphasic interface. The resulting poly(dithiourethane‐amine) adsorbed Pd(II) and Pt(IV) efficiently under acidic conditions due to the high affinity of thiocarbonyl sulfur atoms for soft metal ions. The polymers showed highly selective adsorption of Pd(II) from a mixture of metal ions [Pd(II), Cr(III), Cu(II), Fe(III), Mn(II), Pb(II), and Zn(II)], indicating their potential utilization for selective recovery of rare‐metals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Determination of walnut protein in processed foods by enzyme-linked immunosorbent assay: interlaboratory study

Because food allergens from tree nuts, including walnuts, are a frequent cause of adverse food reactions for allergic patients, the labeling of foods containing ingredients derived from tree nuts is required in numerous countries. According to Japanese regulations, the labeling of food products containing walnuts is recommended. To ensure proper labeling, a novel sandwich ELISA kit for the determination of walnut protein in processed foods (Walnut Protein [2S-Albumin] Kit; Morinaga Institute of Biological Science, Inc.; "walnut kit") has been developed. We prepared seven types of incurred samples (model processed foods: biscuits, bread, sponge cake, orange juice, jelly, chicken meatballs, and rice gruel) containing 10 microg walnut soluble protein/g of food for use in interlaboratory evaluations of the walnut kit. The walnut kit displayed sufficient reproducibility relative standard deviations (interlaboratory precision: 5.8-9.9% RSDR) and a high level of recovery (81-119%) for all the incurred samples. All the repeatability relative standard deviation (RSDr) values for the incurred samples that were examined were less than 6.0%. The results of this interlaboratory evaluation suggested that the walnut kit could be used as a precise and reliable tool for determination of walnut protein in processed foods.     

Cover Picture: Heterogeneously Hybridized Porous Coordination Polymer Crystals: Fabrication of Heterometallic Core–Shell Single Crystals with an In‐Plane Rotational Epitaxial Relationship (Angew. Chem. Int. Ed. 10/2009)

A porous copper coordination framework grew epitaxially as a single crystal on the surface of a single crystal of a porous zinc coordination framework, as described by S. Kitagawa and co‐workers in their Communication on page 1766 ff. The picture shows the structural relationship between the copper and zinc frameworks, which has been unveiled by synchrotron surface X‐ray diffraction measurements; in‐plane rotational epitaxial growth compensates for the different lattice constants of the two crystals.

     

Activation for catalysis of penicillin-binding protein 2a from methicillin-resistant Staphylococcus aureus by bacterial cell wall

Methicillin-resistant Staphylococcus aureus (MRSA) has acquired a unique penicillin-binding protein (PBP), PBP 2a, which has rendered the organism resistant to the action of all available beta-lactam antibiotics. The X-ray structure of PBP 2a shows the active site in a closed conformation, consistent with resistance to inhibition by beta-lactam antibiotics. However, it is known that PBP 2a avidly cross-links the S. aureus cell wall, which is its physiological function. It is shown herein that synthetic fragments of the bacterial cell wall bind in a saturable manner to PBP 2a and cause a conformational change in the protein that makes the active site more accessible to binding to a beta-lactam antibiotic. These observations and measurements point to a novel strategy by nature to keep the active site of PBP 2a sheltered from the inhibitory activity of the antibiotics, yet it becomes available to the polymeric cell wall by a requisite conformational change for the critical cell wall cross-linking reaction.     

Production ofl-aspartic acid byE. coli aspartase immobilized on phenol-formaldehyde resin

Aspartase was extracted from E. coli cells by autolysis in the presence of the substrate. The enzyme could be conveniently immobilized to a weakly basic anion exchange resin Duolite A7 by adsorption. Enzymatic properties of the immobilized aspartase were found to be fit for industrial purposes. Consequently,l-aspartic acid has been industrially produced by this immobilized-enzyme process since 1974.     

Regeneration of atp by immobilized microbial cells and its utilization for the synthesis of ATP and CDP-Choline

A number of fermentative methods for the production of various important nucleotides from their precursors have been developed in Japan, and some of these nucleotides have been industrially produced for more than a decade. For the production of these nucleotides, required ATP is usually supplied to the fermentation media either exogenously or by the naturally occurring ATP regenerating system involved in microbial cells. In this paper, the authors describe an attempt to immobilize ATP-regenerating microbial cells and then utilize such immobilized cells for the continuous production of various nucleotides.     

Novel conjugated polymer containing anthracene backbone: Addition polymer of 9, 10-diethynylanthracene with 9, 10-anthracenedithiol and its properties

9,10-Diethynylanthracene was prepared by the alkaline hydrolysis of 9,10-bis (trimethylsilylethynyl) anthracene. Another new monomer of 9, 10-anthracenedithiol was prepared by the reduction of anthracene polydisulfide. A crystalline conjugated polymer of 9,10-diethynylanthracene with 9,10-anthracenedithiol was synthesized in a THF solution at 50°C by UV irradiation or by using radical initiators. The molecular weight (M?_n) of the insoluble polymer in THF is about 20000–30000 and the soluble is about 4000. From the sulfur content and IR spectrum of the insoluble polymer, it is realized that the obtained polymer has the alternating structure consisting of 9,10-diethynylanthracene and 9,10-anthracenedithiol units. X-ray pattern indicated that the polymer has a layer structure. The conductivity of the undoped polymer was about 10^?11S/cm, but enhanced up to 10^?6 S/cm by doping with iodine. The enhancement of the conductivity seems to be the existence of the CT complex among the polymer backbone and iodine or iodine anion.