1,4‐Benzoquinone Derivatives for Enhanced Bioelectrocatalysis by Fructose Dehydrogenase from Gluconobacter Japonicus: Towards Promising D‐Fructose Biosensor Development

D‐fructose amount in food and beverages should be carefully controlled in order to avoid its overconsumption by human, which can lead to various metabolic diseases. Thus, the development of a low‐cost and portable (bio)sensors, which realize the on‐site monitoring of D‐fructose, is still highly required. In this work, we proposed several reagentless bioelectrochemical systems (BioESs) based on fructose dehydrogenase EC1.1.99.11 from Gluconobacter japonicus (FDH) and on 2‐arylamine‐1,4‐benzoquinone (ABQ) derivatives as a platform for the development of D‐fructose electrochemical biosensor. To design a reliable and easily reproducible BioES, we used the simple physical sorption as the electrode modification strategy for ABQs and FDH immobilization that is suitable for low‐cost mass production of the biosensors by standard microfabrication techniques. To choose the most suitable ABQ compounds for BioESs design, we proposed a novel theoretical approach of potential ET mediator evaluation through its electrochemical properties. A set of newly synthesized and of previously applied ABQs was characterized both electrochemically and using the density functional theory (DFT). It was shown that results obtained by quantum chemical analysis were in a good agreement with the ABQ characteristics obtained in electrochemical measurements. We suggest that the calculated local ionization energy values and theoretical redox potential obtained by DFT are a powerful tool for prediction of ABQs electrochemical properties. The performance of the BioESs with FDH under study was determined by electrochemical and electronic properties of ABQ derivatives and FDH orientation and stabilization on the electrode surface. The most promising BioES was based on carbon paste electrodes and 2‐(3‐nitro(phenyl)amino)‐ cyclohexa‐2,5‐dien‐1,4‐dione as ET mediator, which accelerated FDH catalysis and improved its stability better, then other studied ABQs. The bioelectrocatalytic process was characterized by initial apparent maximum current density of 7.1 μA cm^?2 at the optimal conditions (+400 mV vs. Ag/AgCl, McIlvaine's buffer, pH 5.0 and 20 °C). The findings of this research open new possibilities for development of cost‐effective biosensors with FDH and, potentially, with other redox enzymes.     

Cubic Graphs with Large Circumference Deficit

The circumference of a graph G is the length of a longest cycle. By exploiting our recent results on resistance of snarks, we construct infinite classes of cyclically 4‐, 5‐, and 6‐edge‐connected cubic graphs with circumference ratio bounded from above by 0.876, 0.960, and 0.990, respectively. In contrast, the dominating cycle conjecture implies that the circumference ratio of a cyclically 4‐edge‐connected cubic graph is at least 0.75. Up to our knowledge, no upper bounds on this ratio have been known before for cubic graphs with cyclic edge‐connectivity above 3. In addition, we construct snarks with large girth and large circumference deficit, solving Problem 1 proposed in [J. Hägglund and K. Markström, On stable cycles and cycle double covers of graphs with large circumference, Disc Math 312 (2012), 2540–2544].     

Study of the role of Zn in aromatization of light alkanes with probe molecules

The role of Zn²⁺ in ZnZSM-5 catalyst in the process of aromatization of alkanes has been studied with the probe molecules - n-hexane, cyclohexane and 1-hexene. IR measurements showed that the parent HZSM-5 zeolite contains predominantly Br?nsted acid sites, while Zn cations in ZnZSM-5 catalyst represent Lewis sites. From the results it follows, that Zn cations in ZnZSM-5 catalyst as Lewis acid sites have strong hydro-dehydrogenation activity and they catalyze the dehydrogenation of n-hexane as well as of cyclic intermediates into the corresponding aromatics. From the results of catalytic tests we conclude that the hydro-dehydrogenation activity of the catalyst plays an essential role in aromatization of light alkanes. The results indicate that for improving the yields of aromatics in aromatization of light alkanes on bifunctional catalysts it is inevitable to increase the participation of the dehydrogenation reactions in the activation of alkane as well as in the formation of the corresponding aromatics from cyclic intermediates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coloring Cubic Graphs by Point‐Intransitive Steiner Triple Systems

An ‐coloring of a cubic graph G is an edge coloring of G by points of a Steiner triple system such that the colors of any three edges meeting at a vertex form a block of . A Steiner triple system that colors every simple cubic graph is said to be universal. It is known that every nontrivial point‐transitive Steiner triple system that is neither projective nor affine is universal. In this article, we present the following results.

相似文献   

Exact solution of 3D Timoshenko beam problem using linked interpolation of arbitrary order

For arbitrary polynomial loading and a sufficient finite number of nodal points N, the solution for the 3D Timoshenko beam differential equations is polynomial and given as \({{\varvec \theta} = \sum_{i=1}^N I_i {\varvec \theta}_i}\) for the rotation field and \({{\bf u} = \sum_{i=1}^{N+1} J_i {\bf u}_i}\) for the displacement field, where I _i and J _i are the Lagrangian polynomials of order N?1 and N, respectively. It has been demonstrated in this work that the exact solution for the displacement field may be also written in a number of alternative ways involving contributions of the nodal rotations including \({{\bf u} = \sum_{i=1}^N I_i \left[ {\bf u}_i + \frac 1 N ( {\varvec \theta} - {\varvec \theta}_i ) \times {\bf R}_i \right]}\), where R _i are the beam nodal positions.     

Short cycle covers of graphs and nowhere‐zero flows

A shortest cycle cover of a graph G is a family of cycles which together cover all the edges of G and the sum of their lengths is minimum. In this article we present upper bounds to the length of shortest cycle covers, associated with the existence of two types of nowhere‐zero flows—circular flows and Fano flows. Fano flows, or Fano colorings, are nowhere‐zero ?‐flows on cubic graphs, with certain restrictions on the flow values meeting at a vertex. Such flows are conjectured to exist on every bridgless cubic graph. Copyright © 2011 Wiley Periodicals, Inc. J Graph Theory 68:340‐348, 2011     

Image hiding based on near-optimal moiré gratings

Image hiding based on time-averaged fringes produced by non-harmonic oscillations and near-optimal moiré gratings is presented in this paper. The secret image is embedded into the background moiré grating. Phase matching and initial stochastic phase scrambling algorithms are used to encrypt the image. The decoding of the image is completely visual. The embedded secret image appears when the encrypted image is oscillated in a predefined direction, according to a predefined law of motion. No secret is leaked when the encrypted image is oscillated harmonically at any amplitude of oscillation. The criterion of the optimality of a moiré grating serves as a fitness function for evolutionary algorithms which are used to identify a near-optimal moiré grating for image hiding applications. Numerical experiments are used to illustrate the functionality of the method.     

Influence of Surface-Active Compounds on Starch Dispersion in Water. Part I. Starch Pasting

The influence of native lipids and additives of surface-active compounds on starch paste rheology was investigated. The aim of the study was to gain better understanding of mechanisms involved in starch gelatinization and how these structure changes of granules later affect rheological properties of pastes and gels. Starches from three main sources—potato, maize, and wheat—were tested; sodium dodecylsulfate, oleate, and benzalkonium chloride were employed as additives. Starch pasting was examined by a rheometer to get a viscosity profile, also pastes were analyzed by differential scanning calorimetry, for particle size using a light scattering technique. Results revealed that there was a competition between native lipids and added surfactants for amylose complexation. Complexes formed during gelatinization were strongly affecting granule swelling and dissolution of starch polymers, and viscosity of pastes was mainly dependent on the particle size of a disperse phase in the paste. Addition of strong ionic surfactants to cereal starches resulted in smaller granular remnants and, therefore, decreased viscosity, while the weak anionic surfactant promoted an increase in the particle size and paste viscosity for both cereal and tuber starches. The mechanism of the effect of surfactants on the particle size in pastes is discussed.     

Optimal acyclic edge‐coloring of cubic graphs

An acyclic edge‐coloring of a graph is a proper edge‐coloring such that the subgraph induced by the edges of any two colors is acyclic. The acyclic chromatic index of a graph G is the smallest number of colors in an acyclic edge‐coloring of G. We prove that the acyclic chromatic index of a connected cubic graph G is 4, unless G is K₄ or K_3,3; the acyclic chromatic index of K₄ and K_3,3 is 5. This result has previously been published by Fiam?ík, but his published proof was erroneous.