Detection of hidden hazelnut protein in food by IgY-based indirect competitive enzyme-immunoassay

The development of an indirect competitive enzyme-immunoassay for the detection of hidden hazelnut protein in complex food matrices is described. A sensitive and selective polyclonal antibody was raised by immunisation of laying hens with protein extracts from roasted hazelnuts. In contrast to traditional antibody generation in mammals, the antibody was not isolated from the blood of immunised mammals but from the egg yolk of immunised chickens. A standard calibration curve was optimised using immunoaffinity purified antibody extract and a coating antigen concentration of 10 μg ml⁻¹. One percent skim milk powder was chosen for blocking. The assay has a minimum detection limit of 10 μg l⁻¹, with an IC₅₀ of 618 μg l⁻¹ when a 50 mM phosphate buffer at pH 7.5 and 10 mM sodium chloride is used as assay buffer. The cross reactivity testing shows a high specificity for hazelnut proteins and various foods and food additives were found to be non reactive except beans, sunflower seed or poppy seed.     

Crystal structure of human carboxylesterase 1 complexed with the Alzheimer's drug tacrine: from binding promiscuity to selective inhibition

Human carboxylesterase 1 (hCE1) is a broad-spectrum bioscavenger that plays important roles in narcotic metabolism, clinical prodrug activation, and the processing of fatty acid and cholesterol derivatives. We determined the 2.4 A crystal structure of hCE1 in complex with tacrine, the first drug approved for treating Alzheimer's disease, and compare this structure to the Torpedo californica acetylcholinesterase (AcChE)-tacrine complex. Tacrine binds in multiple orientations within the catalytic gorge of hCE1, while it stacks in the smaller AcChE active site between aromatic side chains. Our results show that hCE1's promiscuous action on distinct substrates is enhanced by its ability to interact with ligands in multiple orientations at once. Further, we use our structure to identify tacrine derivatives that act as low-micromolar inhibitors of hCE1 and may provide new avenues for treating narcotic abuse and cholesterol-related diseases.     

Theoretical study of the cycloaddition of nitrones to cinnamonitrile: effect of Lewis acid coordination on the selectivity of the reaction

A number of quantum chemical and density functional methods have been used to study the chemo- and regioselectivity of the uncatalysed and Lewis acid mediated cycloaddition of the nitrone PhCHN(Me)O with the CC or the CN bond of (E)-cinnamonitrile. In agreement with experimental evidence, Lewis acid coordination to the nitrile strongly promotes reaction at the CN bond over reaction at the alkene moiety. The main factors responsible for this inversion of the chemoselectivity were identified as the following: (i) the Lewis acid strongly stabilises the product of CN addition and the transition state leading to it, thus favouring this reaction both kinetically and thermodynamically. Addition across the CC bond, in contrast, only receives weak kinetic activation; (ii) the cycloaddition to the CC or CN bonds involves different molecular orbitals at the cinnamonitrile, and the Lewis acid influences the orbital involved in CN addition to a larger extent; (iii) the Lewis acid has a stronger effect on the electron distribution of the CN bond. As an overall result, the Lewis acid not only promotes the cycloaddition, but also alters the order of functional group reactivity and brings about a complete change in chemoselectivity.     

Microwave‐Assisted Selenium Dioxide Oxidation of Camphor Derivatives to α‐Dicarbonyl Compounds and Oxoimines

Camphor‐derived α‐dicarbonyl compounds and 3‐oxo‐camphorsulfonylimine have been synthesized from the corresponding ketones or sulfonylimine by microwave‐assisted oxidation with selenium dioxide. Compared to the classical reaction conditions, good yields were obtained in much shorter reaction times. Additionally, the selenium precipitation is more quantitative, and its removal from the reaction mixture is easier.     

Quantum-chemical study of the Lewis acid influence on the cycloaddition of benzonitrile oxide to acetonitrile, propyne and propene

Quantum chemical methods (MP2 and B3LYP) together with a topological analysis of the charge density have been used to study the BH₃- or BF₃-mediated reaction of benzonitrile oxide with acetonitrile, propyne and propene. In the reaction with propene or propyne, addition of Lewis acids has only little influence on the outcome of the reactions. The cycloaddition of nitrile oxides with nitriles, however, is generally promoted by strong Lewis acids. When the Lewis acid coordination takes place at the nitrile oxide the reactant is activated and the product binds weakly to the Lewis acid so that the reaction is expected to be catalytic. In the case of coordination to the nitrile the reaction is Lewis acid mediated. Here the reactant is not much influenced by addition of Lewis acid, but the transition state and the product are stabilised and consequently such processes require a stoichiometric amount of Lewis acid and form a stable Lewis acid-product complex.It has also been demonstrated that the different activation routes for these reactions involve different reaction mechanisms. Whereas the reaction of a Lewis acid coordinated nitrile oxide is of ‘inverse electron demand’, the Lewis acid coordinated nitrile reacts through a ‘normal electron demand’ cycloaddition.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

Insect cold hardiness: a Canadian perspective

The cold climates and diverse environments of Canada have allowed key studies of insect cold hardiness that developed and widened the understanding of this subject. For example, freezing tolerance, chilling tolerance, freezing resistance, supercooling, cryoprotectants and other features can be combined in many different ways, reflecting a wide range of adaptations. Many other factors interact with and influence cold hardiness, such as habitats and their selection, and water and energy balances. These findings suggest several topics that would be especially fruitful for further study in northern Canada.