NIR-based Sudan I to IV and Para-Red food adulterants screening

ABSTRACT

Spices are added in order to enhance the organoleptic characteristics of food and culinary dishes, making them more attractive for consumers. The use of illicit cheap colourants might be profitable along the food supply chain, posing undue risks to human health. This work evaluates the feasibility of NIR spectroscopy with chemometrics as a rapid, simple, non-destructive and affordable screening tool to determine the presence of Sudan I, II, III, IV and Para-red dyes in paprika. The dataset comprised unadulterated and adulterated samples with the five studied dyes at different concentration levels. Several multivariate classification models were built with Linear Discriminant Analysis (LDA) and different machine learning techniques. Preliminary results show that a classifier based on only six wavenumbers is able to determine the presence of some of these dyes in food samples in levels that may represent risk to human health. Sensitivities and specificities above 90% were obtained in almost all cases. These results show the feasibility of inexpensive and portable devices that can be useful for screening out adulterated stock along the food chain supply.     

Ionic Liquids for Propene‐Propane Separation

This paper presents an extensive study on the feasibility of ionic liquids (IL) for the extractive distillation of propene‐propane mixtures. A new experimental method for express screening of non‐volatile entrainers was elaborated. A series of ILs and their mixtures were screened at ambient temperature and low pressures. The screening results show that every tested IL turns a low boiler propene into a high boiler and the alkene‐to‐alkane separation factor can be as low as 0.28. The solubility and separation efficiency can be tuned by adjusting the chemical structures of the ions forming the IL. It was found that shortening of the alkyl substituents of the imidazolium ions leads to a decrease in capacity and to an increase in the separation factor. Interestingly, ILs containing nitrile functionalities in either the cation or the anion showed, in our experiments, enhanced separation ability combined with still good capacities. From our thermodynamic measurements, [EMIM][[B(CN)₄] was proved to be the most promising candidate. Binary mixtures of ILs were also tested and resulted in separation factors and capacities between the values for the individual ILs. For the most promising candidates, also autoclave measurements at elevated temperatures and pressures were carried out. These experiments indicate that the separation ability decreases with growing temperature and loading. In general, our study definitely proves the high potential of ILs to act as entrainers in the extractive distillation of propene‐propane mixtures or for the separation of any other low‐boiling alkene‐alkane mixture.     

Virtual Screening of Specific Insulin-Like Growth Factor 1 Receptor (IGF1R) Inhibitors from the National Cancer Institute (NCI) Molecular Database

Insulin-like growth factor 1 receptor (IGF1R) is an attractive drug target for cancer therapy and research on IGF1R inhibitors has had success in clinical trials. A particular challenge in the development of specific IGF1R inhibitors is interference from insulin receptor (IR), which has a nearly identical sequence. A few potent inhibitors that are selective for IGF1R have been discovered experimentally with the aid of computational methods. However, studies on the rapid identification of IGF1R-selective inhibitors using virtual screening and confidence-level inspections of ligands that show different interactions with IGF1R and IR in docking analysis are rare. In this study, we established virtual screening and binding-mode prediction workflows based on benchmark results of IGF1R and several kinase receptors with IGF1R-like structures. We used comprehensive analysis of the known complexes of IGF1R and IR with their binding ligands to screen specific IGF1R inhibitors. Using these workflows, 17 of 139,735 compounds in the NCI (National Cancer Institute) database were identified as potential specific inhibitors of IGF1R. Calculations of the potential of mean force (PMF) with GROMACS were further conducted for three of the identified compounds to assess their binding affinity differences towards IGF1R and IR.     

High‐Throughput Virtual Screening Using Quantum Mechanical Probes: Discovery of Selective Kinase Inhibitors

A procedure based on semi‐empirical quantum mechanical (QM) calculations of interaction energy is proposed for the rapid screening of compound poses generated by high‐throughput docking. Small molecules (consisting of 2–10 atoms and termed “probes”) are overlapped with polar groups in the binding site of the protein target. The interaction energy values between each compound pose and the probes, calculated by a semi‐empirical Hamiltonian, are used as filters. The QM probe method does not require fixed partial charges and takes into account polarization and charge‐transfer effects which are not captured by conventional force fields. The procedure is applied to screen ～100 million poses (of 2.7 million commercially available compounds) obtained by high‐throughput docking in the ATP binding site of the tyrosine kinase erythropoietin‐producing human hepatocellular carcinoma receptor B4 (EphB4). Three QM probes on the hinge region and one at the entrance pocket are employed to select for binding affinity, while a QM probe on the side chain of the so‐called gatekeeper residue (a hypervariable residue in the kinome) is used to enforce selectivity. The poses with favorable interactions with the five QM probes are filtered further for hydrophobic matching and low ligand strain. In this way, a single‐digit micromolar inhibitor of EphB4 with a relatively good selectivity profile is identified in a multimillion‐compound library upon experimental tests of only 23 molecules.     

High‐Throughput Topographic,Mechanical, and Biological Screening of Multilayer Films Containing Mussel‐Inspired Biopolymers

A high‐content screening method to characterize multifunctional multilayer films that combine mechanical adhesion and favorable biological response is reported. Distinct combinations of nanostructured films are produced using layer‐by‐layer methodology and their morphological, physicochemical, and biological properties are analyzed in a single microarray chip. Inspired by the composition of the adhesive proteins in mussels, thin films containing dopamine‐modified hyaluronic acid are studied. Flat biomimetic superhydrophobic patterned chips produced by a bench‐top methodology are used for the build‐up of arrays of multilayer films. The wettability contrasts imprinted onto the chips are allowed to produce individual, position controlled, multilayer films in the wettable regions. The flat configuration of the chip permits to perform a series of nondestructive measurements directly on the individual spots. In situ adhesion properties are directly measured in each spot, showing that nanostructured films richer in dopamine promote the adhesion. In vitro tests show an enhanced cell adhesion for the films with more catechol groups. The advantages presented by this platform include ability to control the uniformity and size of the multilayers films, its suitability to be used as a new low cost toolbox and for high‐content cellular screening, and capability for monitoring in situ a variety of distinct material properties.     

Computational Library Design for Increasing Haloalkane Dehalogenase Stability

We explored the use of a computational design framework for the stabilization of the haloalkane dehalogenase LinB. Energy calculations, disulfide bond design, molecular dynamics simulations, and rational inspection of mutant structures predicted many stabilizing mutations. Screening of these in small mutant libraries led to the discovery of seventeen point mutations and one disulfide bond that enhanced thermostability. Mutations located in or contacting flexible regions of the protein had a larger stabilizing effect than mutations outside such regions. The combined introduction of twelve stabilizing mutations resulted in a LinB mutant with a 23 °C increase in apparent melting temperature (T_m,app, 72.5 °C) and an over 200‐fold longer half‐life at 60 °C. The most stable LinB variants also displayed increased compatibility with co‐solvents, thus allowing substrate conversion and kinetic resolution at much higher concentrations than with the wild‐type enzyme.     

Solubility Screening on a Series of Structurally Related Compounds: Cosolvent-Induced Changes on the Activity Coefficient of Hydrophobic Solutes

A homologous series of solutes was chosen as a model for a group of structurally related compounds with different physicochemical properties, as is commonly the case during the screening of potential drug candidates. Thermal properties of the crystalline solutes and solubility determinations were used to quantify the two independent factors that determine the solubility of organic compounds: crystallinity and hydrophobicity. A solubility screening study was conducted on the series. By expressing the obtained solubility enhancement expressed as changes in the activity coefficient, it is possible to visually compare the effect of different cosolvents. The results show the importance of solute-solvent polarity match. Polarity match between water miscible cosolvents and hydrophobic compounds is not truly attainable, but comparison of the screening results points out the closest matches (optimal effect), facilitating the systematic evaluation of solubilization approaches.     

Numerical simulation of probing the electric double layer by scanning electrochemical potential microscopy

Computational modeling of probing the electric double layer (EDL) by scanning electrochemical potential microscopy (SECPM) was carried out in order to evaluate the applicability of this method. The modeling is based on a continuum approach for the electric double layer in dilute solution using the modified Poisson-Boltzmann equation. This model takes into account the finite ion size and prevents steric effects near the charged surface. The approach of the SECPM probe towards a charged electrode, immersed in electrolyte solution, is simulated obtaining the potential profile in the direction normal to the electrode. The effects of the shape and the size of the metallic protrusion at the apex of the probe were studied. A clear dependence of the probe potential on the apex geometry was observed, and correlated to the apex surface charge density distribution. The overlap of the EDLs located at the probe and the electrode is studied by setting different initial open circuit potentials, i.e., different charging, to the probe. We have found that the obtained potential profiles are consequences of the EDL overlap, characterized by an ionic distribution in the gap separating the probe and electrode. Depending on the strength of both EDLs and their polarity, the Debye screening effect severely influences the probe potential.     

Use of ionic chromatography in determining the contamination of apple juice by lactic acid

High-performance anion exchange chromatography (HPAEC) with conductometric detection was used for the determination of the lactic acid content of apple juice subjected to fermentation with the strains of Lactobacillus brevis and Lactobacillus plantarum, obtained from a collection, at 20 and 30°C. At the same time, lactate content was determined by means of enzymatic tests and biosensors. Lactic acid concentrations determined by the chromatographic method are similar to those obtained during analysis by enzymatic tests. However, acid concentrations determined by means of biosensors substantially diverge from these results.     

Validation of a multi-residue enzyme-linked immunosorbent assay for qualitative screening of corticosteroids in liver,urine and milk

A rapid and sensitive enzyme-linked immunosorbent assay (ELISA) was applied for the qualitative screening analysis of dexamethasone, betamethasone, flumethasone, and prednisolone in milk and urine, and dexamethasone, flumethasone and prednisolone in liver samples at levels corresponding to the European Union maximum residue limit (MRL), or at required performance levels (RPLs) for substances for which there is no established MRL. Method validation was performed according to Commission Decision 2002/657/EC criteria established for qualitative screening methods. In this regard, the following parameters were determined: detection capability (CCβ), specificity, limit of detection (LOD), limit of quantitation (LOQ), recovery, within-laboratory reproducibility, linearity and ruggedness. LODs were 0.2, 1.2 and 0.6?µg?kg^?1 in milk, urine and liver samples, and LOQ values were 0.3, 1.2 and 1.4?µg?kg^?1 in milk, urine and liver, respectively. Recoveries from spiked samples ranged from 68% to 131% for dexamethasone, from 57% to 120% for flumethasone, from 60% to 155% for betamethasone, and from 23% to 32% for prednisolone, with a coefficient of variation (CV) between 1.6% and 21.2%. The CCβ value was below the MRL/RPL for all examined matrices. Moderate variations of some critical factors in the sample pre-treatment for liver and milk samples were deliberately introduced for ruggedness evaluation and did not result in any negative effects on corticosteroid detection. The proposed method is suitable for qualitative screening analysis of corticosteroids in the above-mentioned food in conformity with the current European Union performance requirements.