A method to detect metal–drug complexes and their interactions with pathogenic bacteria via graphene nanosheet assist laser desorption/ionization mass spectrometry and biosensors

A new method was proposed to probe the interactions between transition metals of Fe(II), Fe(III), Cu(II) with a non steroidal anti-inflammatory drug (NSAID), flufenamic acid (FF) using graphene as a matrix for Graphene assisted laser desorption ionization mass spectrometry (GALDI-MS). Metal–drug complexation was confirmed via UV absorption spectroscopy, fluorescence spectroscopy, pH meter, and change in solution conductivity. The optimal molar ratios for these complexation interactions are stoichiometry 1:2 in both Cu(II) and Fe(II) complexes, and 1:3 in Fe(III) complexes at physiological pH (7.4). Metal complexation of the drug could enhance fluorescence for 20 fold which is due to the charge transfer reaction or increase rigidity of the drug. The main interaction between graphene and flufenamic acid is the П–П interaction which allows us to probe the metal–drug complexation. The GALDI-MS could sensitively detect the drug at m/z 281.0 Da (protonated molecule) with detection limit 2.5 pmol (1.0 μM) and complexation at m/z 661.0, 654.0 and 933.0 Da corresponding to [Cu(II)(FF)₂(H₂O)₂ + H]⁺, [Fe(II)(FF)₂(H₂O)₂ + H]⁺ and [Fe(III) (FF)₃(H₂O)₂ + H]⁺, respectively (with limit of detection (LOD) 2.0 pmol (10.0 μM). Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) spectra show change in the protein profile of intact pathogenic bacteria (Pseudomonas aeroginosa, Staphylococcus aureus). The change in the ionization ability (mainly proton affinity) of pathogenic bacteria may be due to the interactions between the bacteria with the drug (or its complexes). Shielding carboxylic group by metals and increase the hydrophilicity could enhance the biocompatibility of complexes toward the pathogenic bacteria which can be used as biosensors with high sensitivity and lowest detectable concentrations are in the range of 3.3 × 10³–3.9 × 10⁴ cfu mL⁻¹ with large linear dynamic range.     

High CO2 uptake and selectivity by triptycene-derived benzimidazole-linked polymers

Successful incorporation of triptycene into benzimidazole-linked polymers leads to the highest CO(2) uptake (5.12 mmol g(-1), 273 K and 1 bar) by porous organic polymers and results in high CO(2)/N(2) (63) and CO(2)/CH(4) (8.4) selectivities.     

Equilibrium and dynamics of Langmuir monolayers when the interface is a selective solvent: Polystyrene-b-poly(t-butyl acrylate) block copolymers

The surface pressure of monolayers of insoluble diblock copolymers has been measured. One of the blocks is made of poly(t-butyl acrylate) (PtBA), and the other one by polystyrene (PS). The interface is a good solvent for PtBA, while it is a poor solvent for PS. For the sake of comparison, monolayers of a PtBA homopolymer (good solvent conditions) and of poly(4-hydroxy styrene) (P4HS) (poor solvent conditions) have been also measured. It has been found that the relative length of the blocks plays an important role on the shape of the surface pressure Pi versus surface concentration Gamma curves and also on the shape of the equilibrium compressibility versus Gamma curves. However, it does not affect the maximum value of Pi reached at high Gamma's. Surprisingly, the ellipsometric thickness of the copolymer monolayers is almost independent of the relative length of the blocks. The dynamics of the monolayers has been studied by step compression and by surface-light scattering techniques. When M(w,PtBA) > M(w,PS) single exponential relaxations are observed. However, stretched exponentials are obtained for M(w,PS) > or = M(w,PtBA). The relaxation times decrease with increasing Gamma for all the copolymers studied. This is the behavior usually found for poor solvent conditions (P4HS) and opposite to that found for homopolymers under good solvent conditions [PtBA, poly(vinylacetate)]. This means that the solvent quality of the interface does not determine the pressure dependence of tau. The elasticity modulus of the monolayers in the kilohertz range takes values that are similar to those of the high-frequency limit of the relaxation experiments. This means that the relaxation processes have characteristic frequencies below 1 Hz.     

Maternal separation with early weaning: a novel mouse model of early life neglect

Background  

Childhood adversity is associated with increased risk for mood, anxiety, impulse control, and substance disorders. Although genetic and environmental factors contribute to the development of such disorders, the neurobiological mechanisms involved are poorly understood. A reliable mouse model of early life adversity leading to lasting behavioral changes would facilitate progress in elucidating the molecular mechanisms underlying these adverse effects. Maternal separation is a commonly used model of early life neglect, but has led to inconsistent results in the mouse.     

Ant colony optimization for solving an industrial layout problem

This paper presents ACO_GLS, a hybrid ant colony optimization approach coupled with a guided local search, applied to a layout problem. ACO_GLS is applied to an industrial case, in a train maintenance facility of the French railway system (SNCF). Results show that an improvement of near 20% is achieved with respect to the actual layout. Since the problem is modeled as a quadratic assignment problem (QAP), we compared our approach with some of the best heuristics available for this problem. Experimental results show that ACO_GLS performs better for small instances, while its performance is still satisfactory for large instances.     

Preparation and properties of VO2 thin films by a novel sol–gel process

Vanadium dioxide (VO₂) thin films were fabricated using a simple and novel sol–gel process in which V₂O₅ was used as the vanadium source; oxalic acid was used as the reducing agent; and polyvinyl alcohol was used as the film former to control the viscosity of the VO₂ precursor solution and bond vanadium ions. The microstructure and surface morphology of VO₂ films were studied by X-ray diffraction and scanning electron microscopy, respectively. The results showed that using polyvinyl alcohol forms porous nanostructure of VO₂ films with a uniform grain size of ~25 nm. The measured optical reflectance shows well-defined phase transition as observed by an increase of reflectance upon heating above the transition temperature from ~11 to ~30 % at 1,100 nm. Upon cooling, the expected hysteresis is observed.     

Synthesis and application of ionic liquid matrices (ILMs) for effective pathogenic bacteria analysis in matrix assisted laser desorption/ionization (MALDI-MS)

Application of two new series of ionic liquid matrices (ILMs) based on the two most predominantly used conventional organic matrices (Sinapinic acid and 2,5-DHB) in conjugation with various bases (aniline (ANI), dimethyl aniline (DMANI), diethylamine (DEA), dicyclohexylamine (DCHA), pyridine (Pyr), 2-picoline(2-P), 3-picoline(3-P)) for bacterial analysis in matrix assisted laser desorption/ionisation mass spectrometry (MALDI-MS) are reported. The results reveal that ionic liquid matrices could significantly enhance the protein signals, reduce spot-to-spot variation and increase spot homogeneity. More importantly, these novel matrices would not produce any interference during MALDI-MS analysis. Among these ILMs, 2,5-DHB/ANI, 2,5-DHB/DMANI and 2,5-DHB/Pyr can be successfully applied to intact bacterial studies compared with other ILMs. Base molecules when added to conventional matrix can promote proton transfer between the bacterial lysate and the matrices. Due to the enhanced proton transfer efficiency by the ionic liquid matrices, almost all the biomolecules of the intact bacterial cells can be ionized and detected in the MALDI-MS. All synthesized ILMs were characterized using ESI (+)/MS and UV-spectroscopy.