Measurement of nanomolar diphenols by substrate recycling coupled to a pH-sensitive electrode

A new enzyme amplification scheme based on the measurement of the pH-change generated in the laccase/glucose dehydrogenase substrate recycling reaction has been established. Quinone species formed after oxidation of diphenols by laccase are reduced by glucose dehydrogenase in the presence of glucose. Catalytic oxidation of glucose to gluconic acid via gluconolactone leads to a pH-decrease. The utility of the very simple pH-sensitive antimony electrode for monitoring the bienzyme reaction has been shown. The detection limit for norepinephrine and p-aminophenol measured by the bienzyme-modified antimony electrode was 1 nmol/L in the presence of glucose. The enhancement in sensitivity and analytical applications of the proposed scheme are discussed. Permanent address: Department of Biosensors, Research Center for Molecular Diagnostics and Therapy, Simpheropolsky Blvd. 8, 113149 Moscow, Russia     

Single-site catalysis by bimetallic zinc calixarene inclusion complexes

[reaction: see text] Bimetallic alkylzinc calixarene inclusion complexes were prepared and used in the ring-opening polymerization of L-lactide. Polymers with high molecular weight and a low degree of polydispersity were obtained. 1H NMR and diffusion NMR experiments suggest that a single-site mechanism is operative.     

Synthesis of the elusive (R3P)2MF2 (M = Pd, Pt) complexes

The synthesis and characterization of previously unknown palladium(II) and platinum(II) difluoro phosphine complexes are described. These complexes can be obtained either via a halide metathesis reaction with AgF in dichloromethane or by reacting the corresponding dimethyl complexes with XeF2. While the Pt(II) complexes can be prepared with both aryl- and alkyl-phosphine ligands, the stability of the Pd(II) complexes is limited to those having cis-oriented trialkyl phosphine ligands.     

A bienzyme electrode for tyrosine-containing peptides determination

A bienzyme electrode for monitoring biologically important peptides containing tyrosine has been established on the basis of mushroom tyrosinase and quinoprotein glucose dehydrogenase (GDH). Tyrosine residues bound in the peptide chain are oxidized by tyrosinase resulting in consumption of oxygen. Subsequently, the dopaquinone residues are reduced in the GDH catalysed reaction which is driven by an excess of glucose. This reaction cycle leads to a considerable increase of sensitivity. Both enzymes were entraped in poly(vinyl)alcohol matrix and placed on the surface of a Clark-type oxygen electrode (the working platinum electrode was potentiostated at −600 mV) (vs. Ag/AgCl reference electrode) between a polypropylene and cellulose membrane. The bienzyme-modified Clark-type oxygen electrode has a lower detection limit of 0.2 μM for the opioid peptides Tyr-D-Ser-Gly-Phe-Leu-Thr, Leu-enkephalin, Tyr-D-Ala-Gly-Phe-D-Leu and morphiceptin. The dependence of response of the electrode on the length of peptide chain and position of tyrosine residue is discussed. The new electrode has been applied to the quality control of tyrosine containing peptides from pharmaceutical formulations and from peptide synthesis.     

Sequential share bargaining

This paper presents a new extension of the Rubinstein-St?hl bargaining model to the case with n players, called sequential share bargaining. The bargaining protocol is natural and has as its main feature that the players’ shares in the surplus are determined sequentially rather than simultaneously. The protocol also assumes orderly voting, a restriction on the order in which players respond to a proposal. The bargaining protocol requires unanimous agreement for proposals to be implemented. Unlike all existing bargaining protocols with unanimous agreement, the resulting game has unique subgame perfect equilibrium utilities for any value of the discount factor. The result builds on the analysis of so-called one-dimensional bargaining problems. We show that also one-dimensional bargaining problems have unique subgame perfect equilibrium utilities for any value of the discount factor.     

Selected topics in robust convex optimization

Robust Optimization is a rapidly developing methodology for handling optimization problems affected by non-stochastic “uncertain-but- bounded” data perturbations. In this paper, we overview several selected topics in this popular area, specifically, (1) recent extensions of the basic concept of robust counterpart of an optimization problem with uncertain data, (2) tractability of robust counterparts, (3) links between RO and traditional chance constrained settings of problems with stochastic data, and (4) a novel generic application of the RO methodology in Robust Linear Control.      

Catalytic application of zinc complex of oxygen depleted 1,3-bis(pyrazole)-p-tert-butylcalix[4]arene

In this paper we have described the synthesis and coordination properties of monometallic Zinc complex of oxygen depleted bis(pyrazole)-p-tert-butylcalix[4]arene ligand. We also present the catalytic activity of the Zinc–bis(pyrazole) complex, in acetylation of alcohols and lactide polymerization.     

Aryl-halide versus aryl-aryl reductive elimination in Pt(IV)-phosphine complexes

Upon the addition of Br2 to complexes (P-P)Pt(Ar)2, two different products were observed, depending on the bite angle of the bidentate phosphine ligand: a Pt(II) aryl bromide complex, the product of C-Br reductive elimination, and Pt(IV) oxidative addition complex. At high temperatures, the latter exclusively gave the product of the C-C reductive elimination.