Physicochemical characterization of chitin from the Mediterranean flour moth,Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Moth chitin was extracted from adult of the Mediterranean flour moth by alkali-acid treatment and its characteristics were investigated and compared with shrimp chitin because the specific applications of chitin is directly associated with its physicochemical properties. The results revealed that the moth contained significant amounts of chitin but lower amounts of minerals. Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), scanning electron microscopy (SEM) and energy dispersive x-ray diffraction (EDX) were used to investigate physicochemical characteristics of chitin samples. FT-IR spectra revealed that the moth chitin had α-chitin form (anti-parallel chains) with respect to the different orientations of its microfibrils. The degree of acetylation of chitin from moth and shrimp calculated using the FT-IR stretching bands were 70.82% and 71.42%, respectively. The SEM observation exhibited the presence of fibrillar material and porous structures in surface of the chitin samples. EDX analysis revealed that the main elements present in the moth chitin (beyond C, O and N) were Br (10.5%) and Si (9.7%). Our study of enzymatic activity toward colloidal chitin as substrate showed that the extracted chitin from E. kuehniella had high chemical purity as well as commercial chitin.     

The fractional natural decomposition method: theories and applications

In this paper, we propose a new method called the fractional natural decomposition method (FNDM). We give the proof of new theorems of the FNDM, and we extend the natural transform method to fractional derivatives. We apply the FNDM to construct analytical and approximate solutions of the nonlinear time‐fractional Harry Dym equation and the nonlinear time‐fractional Fisher's equation. The fractional derivatives are described in the Caputo sense. The effectiveness of the FNDM is numerically confirmed. Copyright © 2016 John Wiley & Sons, Ltd.     

TiO<Subscript>2</Subscript> nanoparticles doped with Celestine Blue as a label in a sandwich immunoassay for the hepatitis C virus core antigen using a screen printed electrode

The authors describe an electrochemical immunoassay for the core antigen of hepatitis C virus (HCV). The method is based on the use of a screen-printed carbon electrode (SPCE) that was modified with a Nafion@TiO₂ nanocomposite and loaded with secondary antibody (Ab2) to entrap Celestine Blue (CB). The material has architecture of the type CB/Ab2/Nafion@TiO₂. A nanocomposite consisting of graphene, ionic liquid and fullerene was deposited on the SPCE first, and rhodium nanoparticles (RhNPs) were then deposited on the surface of modified electrode in order to immobilize primary antibody (Ab1). The antigen and CB/Ab2/Nafion@TiO₂ were conjugated one by one to form a sandwich-type immunocomplex. The signal was obtained by differential pulse voltammetry whose intensity is related to the concentration of the antigen. The assay, if operated at a working voltage of typically 0.35 V (vs. Ag/AgCl) has a response that is linear in the 0.1 to 250 pg?mL^?1 HCV core antigen concentration range, and the limit of detection is as low as 25 fg?mL^?1. The assay was applied to the determination of the HCV core antigen in spiked human serum samples. In our perception, the method represents a promising platform for the detection of various antigens if appropriate antibodies are available.

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Graphical abstract An electrochemical immunoassay for the core antigen of Hepatitis C virus was studied. A nanocomposite consisting of graphene, ionic liquid and fullerene was deposited on the SPCE and rhodium nanoparticles were deposited on the surface of modified electrode in order to immobilize primary antibody. Nafion@TiO₂ was loaded with secondary antibody to entrap Celestine Blue.

     

Unusual product from the acid-catalyzed one-pot,multicomponent reaction of thiocarbohydrazide,aldehydes, and phenacyl bromides

A one-pot, three-component protocol for the synthesis of novel five-membered thiazole ring bonded to two hydrazone motifs is described. The acid-catalyzed reaction of one equivalent of thiocarbohydrazide, two equivalents of aromatic aldehydes, and one equivalent of phenacyl bromides afforded the five-membered thiazole ring. The reactions proceed with novel chemoselectivity. Similar reported protocols have always afforded 1,3,4-thiadiazines.     

Polymer-Enhanced Capillary Transient Isotachophoresis with Boronic Acid-Functionalized Squarylium Dyes for the Fluorescent Determination of Digoxin and Digoxigenin

Here is reported a new application of polymer-enhanced capillary transient isotachophoresis for the separation and quantification of the drug digoxin and its primary metabolite digoxigenin coupled with laser-induced fluorescence (LIF) detection facilitated by labeling with two boronic acid-functionalized squarylium dyes of different alkyl side chain lengths, SQ-BA1 and SQ-BA2. The conditions for drug–dye complex formation were optimized, as determined by absorbance and fluorescence spectra, according to solution pH and buffer composition. As digoxin has a digitoxose sugar moiety in its structure, it was shown to exhibit better enhancement in the fluorescence intensity of both dyes than digoxigenin, which lacks this moiety, presumably through the formation of a cyclic boronate ester complex. A comparison of analyte labeling in pre-column and on-column modes was conducted in subsequent capillary electrophoresis-LIF studies, with the latter labeling mode yielding superior sensitivity. However, to achieve the complete resolution of labeled digoxin and digoxigenin analytes, it was necessary to use the modified isotachophoresis method, with added borate ions that may differentially interact with the drug and its metabolite, hence affecting their mobilities. Limits of quantification of the method for the determination of digoxin with SQ-BA1 and SQ-BA2 were 2.61?×?10^?3 and 2.82?×?10^?3?M and limits of detection were 7.83?×?10^?4 and 8.47?×?10^?4?M while sensitivities were as great as 5.06?×?10⁹ and 2.89?×?10⁹?M^?1, respectively, indicating that the method is suitable for practical analysis.     

Thermal radiation effects on MHD flow of a micropolar fluid over a stretching surface with variable thermal conductivity

In this paper, the effects of variable thermal conductivity and radiation on the flow and heat transfer of an electrically conducting micropolar fluid over a continuously stretching surface with varying temperature in the presence of a magnetic field are considered. The surface temperature is assumed to vary as a power-law temperature. The governing conservation equations of mass, momentum, angular momentum and energy are converted into a system of non-linear ordinary differential equations by means of similarity transformation. The resulting system of coupled non-linear ordinary differential equations is solved numerically. The numerical results show that the thermal boundary thickness increases as the thermal conductivity parameter S$S$ increases, while it decreases as the radiation parameter F$F$ increases. Also, it was found that the Nusselt number increases as F$F$ increases and decreases as S$S$ increases.     

Synthesis of tacrine derivatives under solventless conditions

Effects of microwave irradiation on the solid‐phase synthesis of tacrine and its derivatives have been evaluated. Preparation of tacrine analogues under conventional conditions suffers from poor synthetic efficiency and usually gives low yield. Reaction of substituted anthranilonitrile with cyclohexanone under microwave irradiation gave a good to excellent yield of the corresponding substituted 9‐amino‐1,2,3,4‐tetrahydroacridines.     

Sculpting the bicyclo[3.1.0]hexane template of carbocyclic nucleosides to improve recognition by herpes thymidine kinase

The replacement of the furanose ring by a cyclopentane in nucleosides generates a group of analogues known generically as carbocyclic nucleosides. These compounds have increased chemical and enzymatic stability due to the absence of a true glycosyl bond that characterizes conventional nucleosides. The additional fusion of a cyclopropane ring to the cyclopentane produces a bicyclo[3.1.0]hexane system that depending on its location relative to the nucleobase is able to lock the embedded cyclopentane ring into conformations that mimic the typical north and south conformations of the furanose ring in conventional nucleosides. These bicyclo[3.1.0]hexane templates have already provided important clues to differentiate the contrasting conformational preferences between kinases and polymerases. Herein, we describe the design, synthesis, and phosphorylation pattern of a new bicyclo[3.1.0]hexane thymidine analogue that seems to possess an ideal spatial distribution of pharmacophores for an optimal interaction with herpes simplex 1 thymidine kinase. The bicyclo[3.1.0]hexane template represents a privileged rigid template for sculpting other carbocyclic nucleosides to meet the demands of specific receptors.     

Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine

Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.