Application of support vector machines to 1H NMR data of fish oils: methodology for the confirmation of wild and farmed salmon and their origins

Support vector machines (SVMs) were used as a novel learning machine in the authentication of the origin of salmon. SVMs have the advantage of relying on a well-developed theory and have already proved to be successful in a number of practical applications. This paper provides a new and effective method for the discrimination between wild and farm salmon and eliminates the possibility of fraud through misrepresentation of the country of origin of salmon. The method requires a very simple sample preparation of the fish oils extracted from the white muscle of salmon samples. (1)H NMR spectroscopic analysis provides data that is very informative for analysing the fatty acid constituents of the fish oils. The SVM has been able to distinguish correctly between the wild and farmed salmon; however ca. 5% of the country of origins were misclassified.     

Selecting the optimum number of partial least squares components for the calibration of attenuated total reflectance-mid-infrared spectra of undesigned kerosene samples

Selecting the correct dimensionality is critical for obtaining partial least squares (PLS) regression models with good predictive ability. Although calibration and validation sets are best established using experimental designs, industrial laboratories cannot afford such an approach. Typically, samples are collected in an (formally) undesigned way, spread over time and their measurements are included in routine measurement processes. This makes it hard to evaluate PLS model dimensionality. In this paper, classical criteria (leave-one-out cross-validation and adjusted Wold's criterion) are compared to recently proposed alternatives (smoothed PLS-PoLiSh and a randomization test) to seek out the optimum dimensionality of PLS models. Kerosene (jet fuel) samples were measured by attenuated total reflectance-mid-IR spectrometry and their spectra where used to predict eight important properties determined using reference methods that are time-consuming and prone to analytical errors. The alternative methods were shown to give reliable dimensionality predictions when compared to external validation. By contrast, the simpler methods seemed to be largely affected by the largest changes in the modeling capabilities of the first components.     

The mechanical properties of crystalline cyclopentyl polyhedral oligomeric silsesquioxane

The anisotropic elastic constants of crystalline octacyclopentyl polyhedral oligomeric silsesquioxane (CpPOSS) were determined using molecular dynamics. The force field used for these calculations was shown to model accurately the rhombohedral and triclinic crystal structures of octasilsesquioxane and CpPOSS, respectively, as well as the vibrational frequencies of octasilsesquioxane. The moduli for CpPOSS are anisotropic, with a Reuss-averaged bulk modulus of 7.5 GPa, an isotropic averaged Young's modulus of 11.78 GPa, and an isotropic averaged shear modulus of 4.75 GPa. These isotropic averages or, alternatively, the full anisotropic stiffness tensor of the crystal can be used with micromechanical composite models to calculate the effective elastic properties of polymer nanocomposites that contain crystalline aggregates of CpPOSS.     

Investigating the oxidation of alkenes by non-heme iron enzyme mimics

Iron is emerging as a key player in the search for efficient and environmentally benign methods for the functionalisation of C-H bonds. Non-heme iron enzymes catalyse a diverse array of oxidative chemistry in nature, and small-molecule complexes designed to mimic the non-heme iron active site have great potential as C-H activation catalysts. Herein we report the synthesis of a series of organic ligands that incorporate key features of the non-heme iron active site. Iron(ii) complexes of these ligands have been generated in situ and their ability to promote hydrocarbon oxidation has been investigated. Several of these systems promote the biomimetic dihydroxylation of cyclohexene at low levels, when hydrogen peroxide is used as the oxidant; allylic oxidation products are also observed. An investigation of ligand stability reveals formation of several breakdown products under the conditions of the oxidative turnover reactions. These products arise via oxidative decarboxylation, dehydration and deamination reactions. Taken together these results indicate that competing mechanisms are at play with these systems: biomimetic hydroxylation involving high-valent iron species, and allylic oxidation via Fenton chemistry and Haber-Weiss radical pathways.     

Plasma and beam facility atomic oxygen erosion of a transition metal complex

Glassy residues of the complex bis(N,N-disalicylidene-1,2-phenylenediamino)zirconium(IV), Zr(dsp)₂, on glass slides were exposed to atomic oxygen in a plasma asher or an atomic beam facility for various amounts of lime in order to study the erosion process, determine the rate of erosion, and learn the chemical identity of the residue. The exposed films were characterized by weight loss, optical photography, profilometry, diffuse reflectance and total transmittance spectroscopy, scanning electron microscopy (SEM) with wavelength dispersive X-ray spectrometry (WDS), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Results indicate that these films erode much more slowly polyimide (Kapton) film under identical conditions, that the erosion is very nonuniform, and that zirconium dioxide is the predominant product after extended exposure. This complex is currently being evaluated as a polymer additive.     

Determination of metoprolol and its alpha-hydroxide metabolite in serum by reversed-phase high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for the simultaneous quantitation of metoprolol and alpha-hydroxymetoprolol concentrations in serum is developed. Analysis is performed on a C18 column using a 70:30 mixture of two solutions, A and B respectively. Solution A is 1 L of a 1% acetic acid solution with 25 mL of 0.005 M 1-heptanesulfonic acid. Solution B is 1 L of acetonitrile with 25 mL of 0.005 M 1-heptanesulfonic acid. Column effluent is monitored by fluorescence detection at an excitation wavelength of 225 nm. A 320-nm band pass filter is employed. The limit of sensitivity is approximately 2 ng/mL for both compounds. No potential sources of interference are identified. A coefficient of variation of less than 10% is observed on replicate determinations at 10 ng/mL for both compounds and at 300 and 180 ng/mL for metoprolol and alpha-hydroxymetoprolol, respectively. The method has the advantages of complete resolution of the metabolite of metoprolol, a high degree of reproducibility, adequate sensitivity, and an easily accessible internal standard.     

Rules of Macrocycle Topology: A [13]‐Macrodilactone Case Study

Shape is an inherent trait of a molecule that dictates how it interacts with other molecules, either in binding events or intermolecular reactions. Large‐ring macrocyclic compounds in particular leverage their shape when they are selectively bound by biomolecules and also when they exhibit macrocyclic diastereoselectivity. Nonetheless, rules that link structural parameters to the conformation of a macrocycle are still rudimentary. Here we use a structural investigation of a family of [13]‐macrodilactones as a case study to develop rules that can be applied generally to macrocycles of different sizes and with a variety of functionality. A characteristic “ribbon” shape is adopted by the [13]‐macrodilactones in the absence of stereogenic centres, which exhibits planar chirality. When one stereogenic centre at key positions on the backbone is incorporated into the structure, the planar chirality is dictated by the configuration of the centre. In cases where two stereogenic centres are present, their relationships can either reinforce the characteristic ribbon shape or induce alternative shapes to be adopted. The rules established in the case study are then applied to the analysis of a structure of the natural product migrastatin. They lay the groundwork for the development of models to understand macrocycle‐biomolecule interactions and for the preparation of macrocycles with designed properties and activities.     

Incorporation of Bulky and Cationic Cyclam-Triazole Moieties into Marimastat Can Generate Potent MMP Inhibitory Activity without Inducing Cytotoxicity

The synthesis and matrix metalloproteinase (MMP) inhibitory activity of a cyclam–marimastat conjugate and its metal complexes are described. The conjugate, synthesized with a copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (“click” reaction), contains two zinc-binding groups (ZBGs). The metal complexation behavior with copper(II) and zinc(II) was investigated using UV/Vis spectrophotometry and ¹H NMR spectroscopy, respectively, demonstrating that the first equivalent of the metal ion was chelated by the cyclam-triazole moiety rather than the hydroxamic acid site. Thus, the corresponding mononuclear metal–cyclam complexes were successfully prepared with one equivalent of the metal salt. Both the cyclam–marimastat conjugate and its metal complexes exhibited slightly reduced potency against MMP-1, but essentially identical inhibitory activity against MMP-3. The conjugate and its metal complexes displayed little or no cytotoxicity, further supporting their potential suitability for imaging MMP localization and activity. To the best of our knowledge, this is the first report that describes the incorporation of metal complexes into an MMP inhibitor without influencing the preexisting ZBG, and the first report of the evaluation of structures containing more than one ZBG as MMP inhibitors.