Concentration changes of organochlorine compounds and polybromodiphenyl ethers during metamorphosis of aquatic insects

The role of insect larvae and pupae as sources of organochlorine compounds (OCs) and polybromodiphenyl ethers (PBDEs) in freshwater food webs for high predators such as fish is evaluated. Trichoptera and diptera have been taken as organisms of choice for such comparison because they are common in benthic aquatic habitats and accumulate substantial amounts of these compounds. Hexachlorobenzene, hexachlorocyclohexanes,4,4'-DDE,4,4'-DDT, polychlorobiphenyls, and PBDEs have been measured. The results show a nonselective enrichment of OCs and PBDEs from larvae to pupae. These concentration increases may result from the weight loss of pupae during metamorphosis as a consequence of mainly protein carbon respiration and lack of feeding. Despite the lack of change in total amount, the concentration increases from larvae to pupae are very relevant for the pollutant ingestion of the higher predators. The intakes of OCs and PBDEs by trout are between 2- and 5-fold higher per calorie gained when predating on pupae than on larvae. Since pollutant concentration, energy reward, predation susceptibility, and duration of life stage are very different between these two insect stages, and none of them is irrelevant for the incorporation of OCs or PBDEs to higher levels, bioaccumulation food-web models should distinguish between the two sources.     

Effect of polymer topology on the curing process and mechanical characteristics of epoxy thermosets modified with linear or multiarm star poly(ε-caprolactone)

A well-defined multiarm star copolymer, hyperbranched poly(glycidol)-b-poly(ε-caprolactone), with an average of 100-110 arms per molecule and a molecular weight of arms of 1000 g/mol (s-PCL) and a linear PCL analog (l-PCL) were used as modifiers in the curing of diglycidylether of bisphenol A (DGEBA) using ytterbium triflate as cationic initiator. The effect of the polymer topology on the curing and gelation was studied by dynamic scanning calorimetry (DSC) and rheometry. The addition of s-PCL to the resin left the complex viscosity (η∗) practically unaltered. In contrast the addition of l-PCL incremented substantially the viscosity. The addition of star-shaped modifiers decreased the shrinkage after gelation in a higher extent than the linear analog. The homogeneity of pure DGEBA and modified thermosets was proved by dynamic thermomechanical analysis (DMTA) and electronic microscopy (SEM). The addition of star-like structures led to a higher impact energy fracture in comparison to pure DGEBA and l-PCL modified thermosets and to a lower effect on the microhardness than the linear analog.     

Dyeing behaviour of relaxed and retractile components in high-bulk yarns

The evolution of dye absorption and fine structure variations due to heat treatment in high-bulk yarns was studied. Two acrylic fibres of different commercial origin were employed. Using these, the following yarns were spun: 100% relaxed (N), 100% retractile (R), 55:45 N/R and 45:55 N/R. The evolution of fibre microstructure induced by the dyeing process was studied through the differential solubility technique in mixtures of dimethylformamide and water.     

Toward a Novel Drug To Target the EGF–EGFR Interaction: Design of Metabolically Stable Bicyclic Peptides

In cancer, proliferation of malignant cells is driven by overactivation of growth‐signalling mechanisms, such as the epidermal growth factor receptor (EGFR) pathway. Despite its therapeutic relevance, the EGF–EGFR interaction has remained elusive to inhibition by synthetic molecules, mostly as a result of its large size and lack of binding pockets and cavities. Designed peptides, featuring cyclic motifs and other structural constraints, have the potential to modulate such challenging protein–protein interactions (PPIs). Herein, we present the structure‐based design of a series of bicyclic constrained peptides that mimic an interface domain of EGFR and inhibit the EGF–EGFR interaction by targeting the smaller partner (i.e., EGF). This design process was guided by the integrated use of in silico methods and biophysical techniques, such as NMR spectroscopy and surface acoustic wave. The best analogues were able to reduce selectively the viability of EGFR+ human cancer cells. In addition to their efficacy, these bicyclic peptides are endowed with exceptional stability and metabolic resistance—two features that make them suitable candidates for in vivo applications.     

The incorporation of quantum effects in enzyme kinetics modeling

We present an overview of new procedures for including quantum mechanical effects in enzyme kinetics. Quantum effects are included in three ways: (1) The electronic structure of the atoms in the catalytic center is treated quantum mechanically in order to calculate a realistic potential energy surface for the bond rearrangement process. (2) The discrete nature of quantum mechanical vibrational energies is incorporated in the treatment of nuclear motion for computing the potential of mean force. (3) Multidimensional tunneling contributions are included. These procedures are illustrated by applications to proton abstractions catalyzed by enolase and methylamine dehydrogenase and hydride-transfer reactions by alcohol dehydrogenase and xylose isomerase.     

Determination of the Synthetic Cannabinoids JWH-122, JWH-210, UR-144 in Oral Fluid of Consumers by GC-MS and Quantification of Parent Compounds and Metabolites by UHPLC-MS/MS

The consumption of synthetic cannabinoids (SCs) has significantly increased in the last decade and the analysis of SCs and their metabolites in human specimens is gaining interest in clinical and forensic toxicology. A pilot study has been carried out using a combination of an initial last generation gas chromatography-mass spectrometry (GC-MS) screening method for the determination of JWH-122, JWH-210, UR-144) in oral fluid (OF) of consumers and an ultra-high performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS) confirmatory method for the quantification of the parent compounds and their metabolites in the same biological matrix. OF samples were simply liquid-liquid extracted before injecting in both chromatographic systems. The developed methods have been successfully validated and were linear from limit of quantification (LOQ) to 50 ng/mL OF. Recovery of analytes was always higher than 70% and matrix effect always lower than 15% whereas intra-assay and inter-assay precision and accuracy were always better than 16%. After smoking 1 mg JWH-122 or UR-144 and 3 mg JWH-210, maximum concentration of 4.00–3.14 ng/mL JWH-122, 8.10–7.30 ng/mL JWH-210 ng/mL and 7.40 and 6.81 ng/mL UR-144 were measured by GC-MS and UHPLC-HRMS respectively at 20 min after inhalation. Metabolites of JWH 122 and 210 were quantified in OF by UHPLC-HRMS, while that of UR144 was only detectable in traces. Our results provide for the first time information about disposition of these SCs and their metabolites in consumers OF. Last generation GC-MS has proven useful tool to identify and quantify parent SCs whereas UHPLC-HRMS also confirmed the presence of SCs metabolites in the OF of SCs consumers.     

N‐Lauroylation during the Expression of Recombinant N‐Myristoylated Proteins: Implications and Solutions

Incorporation of myristic acid onto the N terminus of a protein is a crucial modification that promotes membrane binding and correct localization of important components of signaling pathways. Recombinant expression of N‐myristoylated proteins in Escherichia coli can be achieved by co‐expressing yeast N‐myristoyltransferase and supplementing the growth medium with myristic acid. However, undesired incorporation of the 12‐carbon fatty acid lauric acid can also occur (leading to heterogeneous samples), especially when the available carbon sources are scarce, as it is the case in minimal medium for the expression of isotopically enriched samples. By applying this method to the brain acid soluble protein 1 and the 1–185 N‐terminal region of c‐Src, we show the significant, and protein‐specific, differences in the membrane binding properties of lauroylated and myristoylated forms. We also present a robust strategy for obtaining lauryl‐free samples of myristoylated proteins in both rich and minimal media.