Quantitative-competitive polymerase chain reaction coupled with slab gel and capillary electrophoresis for the detection of roundup ready soybean and maize

The aim of the present study was to develop a quantitative-competitive PCR (QC-PCR) method to detect DNA from transgenic herbicide-resistant (roundup ready, RR) soybean and maize. Since no QC-PCR system for the quantification of RR maize had been published at the time of writing, a specific competitor DNA for transgenic event was developed. For the QC-PCR of RR-soybean, a commercially available competitor was employed. These internal standards were calibrated by coamplifying with mixtures containing RR-soybean and maize DNAs. The calibrated QC-PCR systems were applied to certified RR-soybean and maize flour mixtures in order to demonstrate their suitability not only for the quantification of the glyphosate resistance traits in DNA matrices, but also in practically relevant samples. In addition, a special focus of the present work was to compare the detection of QC-PCR products by slab gel and CGE with UV detection. CGE permitted the precise detection of transgenic events also below the equivalence points; while in slab gel electrophoresis, due to the low sensitivity the quantification of genetically modified DNA was allowed only at the equivalence point.     

Competitive binding of cadmium by plant thiols: an electrochemical study assisted by multivariate curve resolution

Multivariate curve resolution with alternating least squares (MCR-ALS) has been applied to voltammetric data obtained from analysis of the competitive binding of cysteine (Cys) and cysteine–glycine (Cys-Gly) by Cd(II) as a first approach towards mixtures of phytochelatins and related compounds in natural media. From different starting points, the possibilities of formation of mixed complexes and/or displacements between ligands are investigated. Analysis of the resulting unitary voltammograms and concentration profiles of the resolved components by MCR-ALS suggests that the strongest ligand (Cys-Gly) is able to displace the weakest (Cys) from its metal complexes, whereas this does not happen in the opposite direction. On the other hand, no evidence of Cd mixed-ligand complexes was found. Figure Differential pulse polarograms measured in the independent titrations of 1 × 10^-5 mol L^-1 Cys, 1 × 10^-5 mol L^-1 Cys-Gly, and a mixture of Cys-Gly (0.5 × 10^-5 mol L^-1) and Cys (1 × 10^-5 mol L^-1) with Cd²⁺, at TRIS-HNO₃ buffer (0.1 mol L^-1 and PH 7.5) in the presence of 0.1 mol L^-1 KNO₃     

Adsorptive denitrogenation of indole from model fuel oil over Co-MAC: Adsorption mechanisms and competitive adsorption

The present research article depicts the adsorptive denitrogenation of indole-containing model oil using cobalt-incorporated acid-activated carbon (Co-MAC). The active metal incorporated acetic acid-activated bio-sorbent showed a significant adsorption capacity for indole from model fuel oil than mere activated carbon. In a batch study, maximum 96% indole removal was achieved with an initial indole concentration of 500 mg/L, catalyst dose of 10 g/L, time of 4 h, and reaction temperature of 303 K. The non-linear regression analysis was opted to fit the experimental equilibrium data into various adsorption isotherms, including Langmuir, Freundlich, Temkin and Redlich, and Peterson. Thermodynamic parameters of adsorption were investigated, and the entropy and heat of adsorption change were determined to be 0.26 kJ/mol K and 57.31 kJ/mol, respectively. Besides, a plausible adsorption mechanism of indole was also explored.     

Stabilization of Guest Molecules inside Cation-Lidded Cucurbiturils Reveals that Hydration of Receptor Sites Can Impede Binding

Docking of alkali metal ions to water-soluble macrocyclic receptors generally reduces the affinity of guest molecules due to competitive binding. The idea that solvation water molecules could display a larger steric hindrance towards guest binding than cations has not been considered to date. We show that the docking of large cations to cucurbit[5]uril (CB5) unexpectedly increases (by a factor of 5–8) the binding of hydrophobic guests, methane and ethane. This is due to the removal of water molecules from the carbonyl portals of CB5 during cation binding, which frees up space for hydrophobe encapsulation. In contrast, smaller cations like sodium protrude deeply into the cavity of CB5 and cause the expected decrease in binding, such that the rational selection of alkali cations allows for a variation of up to a factor of 20 in binding of methane and ethane. The statistical analysis of crystallographic data shows that the cavity volume of CB5 can be enlarged by placing large alkali ions (Rb⁺ and Cs⁺) centro-symmetrically at the portals. The results reveal a hitherto elusive steric hindrance of solvation water molecules near receptor binding sites, which is pertinent for the design of supramolecular catalysts and the understanding of biological receptors.     

Dynamics of a Discrete Two-species Competitive Model with Michaelies-Menten Type Harvesting in the First Species

In this paper, we use a semidiscretization method to derive a discrete two-species competitive model with Michaelis-Menten type harvesting in the first species. First, the existence and local stability of fixed points of the system are investigated by employing a key lemma. Subsequently, the transcritical bifurcation, period-doubling bifurcation and pitchfork bifurcation of the model are investigated by using the Center Manifold Theorem and bifurcation theory. Finally, numerical simulations are presented to illustrate corresponding theoretical results.     

Janus-Type ESIPT Chromophores with Distinctive Intramolecular Hydrogen-bonding Selectivity

Excited-state intramolecular proton transfer (ESIPT)-based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus-type ESIPT chromophores featuring distinctive hydrogen bond (H-bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H-bonds with imines in imine-modified 2-hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone-modified HBT chromophores. Imine-derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone-derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H-bonds and their impact on the ESIPT process. This Janus-type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.     

Global Bifurcation for a Class of Lotka-Volterra Competitive Systems

For a class of Lotka-Volterra competitive systems including both diffusion and advection, a global bifurcation result of positive steady states is established via a bifurcation approach. Also, the phenomenon of multiple positive steady states is discussed.