Visible diode laser induced fluorescence detection of doxorubicin in plasma using pressurized capillary electrochromatography

Pressurized capillary electrochromatography is a variant of capillary electrochromatography (CEC) in which the driving force is both electroosmotic and hydraulic. The inlet of the CEC capillary is pressurized using an HPLC pump, and an electric field is simultaneously applied. This work describes a method for the analysis of doxorubicin. Doxorubicin was reacted with Cy5.29.OSu in acetonitrile. The derivative was confirmed by RP-TLC. A CEC system equipped with a VDLIF detector was constructed and used to analyze the derivative. The reaction mixture was injected onto a capillary packed in-house with 3 microm C-18 Luna particles and separation was carried out at 25 kV using 70% acetonitrile/ 30% phosphate (10 mM, pH = 4.8) as the mobile phase. The derivatization reaction was optimized by the investigation of parameters such as reaction time, temperature and concentration of label in order to increase the yield of the derivative. The optimal conditions were determined to be 30 min, 80 degrees C and 50 nmol/mL, respectively. Doxorubicin was extracted from plasma using solid-phase extraction under alkaline conditions, derivatized and injected onto the CEC-VDLIF system. The selectivity of the assay was demonstrated by a lack of interfering peaks due to plasma constituents across the elution window of the derivative peak in blank plasma extracts (n = 6 sources). The limit of detection (LOD) of the assay in plasma calculated as 3 s(b)/m was determined to be 1.7 ng/mL. The precision of the assay determined at a concentration of 167.7 ng/mL (n = 5) was found to be within 7.04 %RSD.     

The effective thermal conductivity of carbon nanotube composites

The effective thermal conductivity of Carbon Nanotube (CNT)-polymer composites has been estimated using analytical and computational models. The analytical approach is based on the Cascade Continuum Micromechanics (CCM) model formulated within the framework of mean-field homogenization and the computational approach is based on numerical homogenization of the composite microstructure using image based Voxel-FEM (Finite Element Method). Comparison of the analytical and computational model predictions with experimental data show that the interfacial thermal resistance is overestimated by the analytical model as a consequence of not taking into account the CNT fiber tortuosity (curviness). (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Chaperones mainly suppress primary nucleation during formation of functional amyloid required for bacterial biofilm formation

Unlike misfolding in neurodegenerative diseases, aggregation of functional amyloids involved in bacterial biofilm, e.g. CsgA (E. coli) and FapC (Pseudomonas), is carefully regulated. However, it is unclear whether functional aggregation is inhibited by chaperones targeting pathological misfolding and if so by what mechanism. Here we analyze how four entirely different human chaperones or protein modulators (transthyretin, S100A9, Bri2 BRICHOS and DNAJB6) and bacterial CsgC affect CsgA and FapC fibrillation. CsgA is more susceptible to inhibition than FapC and the chaperones vary considerably in the efficiency of their inhibition. However, mechanistic analysis reveals that all predominantly target primary nucleation rather than elongation or secondary nucleation, while stoichiometric considerations suggest that DNAJB6 and CsgC target nuclei rather than monomers. Inhibition efficiency broadly scales with the chaperones'' affinity for monomeric CsgA and FapC. The chaperones tend to target the most aggregation-prone regions of CsgA, but do not display such tendencies towards the more complex FapC sequence. Importantly, the most efficient inhibitors (Bri2 BRICHOS and DNAJB6) significantly reduce bacterial biofilm formation. This commonality of chaperone action may reflect the simplicity of functional amyloid formation, driven largely by primary nucleation, as well as the ability of non-bacterial chaperones to deploy their proteostatic capacities across biological kingdoms.

Unlike misfolding in neurodegenerative diseases, aggregation of functional amyloids involved in bacterial biofilm, e.g. CsgA (E. coli) and FapC (Pseudomonas), is carefully regulated.     

In Vitro Antibacterial Activity of Green Synthesized Silver Nanoparticles Using Azadirachta indica Aqueous Leaf Extract against MDR Pathogens

Rice is the most important staple food crop feeding more than 50% of the world’s population. Rice blast is the most devastating fungal disease, caused by Magnaporthe oryzae (M. oryzae) which is widespread in rice growing fields causing a significant reduction in the yield. The present study was initiated to evaluate the effect of green synthesized silver nanoparticles (AgNPs) on the biochemical constituents of rice plants infected with blast. AgNPs were synthesized by using Azadirachta indica leaf extract and their characterization was performed using UV-visible spectroscopy, particle size analyser (PSA), scanning electron microscope (SEM), and X-ray diffraction (XRD) which confirmed the presence of crystalline, spherical shaped silver nanoparticles with an average size of 58.9 nm. After 45 days of sowing, artificial inoculation of rice blast disease was performed. After the onset of disease symptoms, the plants were treated with AgNPs with different concentrations. Application of nanoparticles elevated the activity of antioxidative enzymes such as superoxide dismutase, catalase, peroxidase, glutathione reductase, and phenylalanine ammonia-lyase compared to control plants, and total phenol and reducing sugars were also elevated. The outcome of this study showed that an increase in all biochemical constituents was recorded for A. indica silver nanoparticles-treated plants. The highest values were recorded in 30 ppm and 50 ppm AgNPs-treated plants, which showed the highest resistance towards the pathogen. Green synthesized AgNPs can be used in future for disease control in susceptible varieties of rice. The synthesized AgNPs using A. indica leaf extract have shown promising antibacterial activity when tested against 14 multidrug-resistant (MDR) bacteria comprising Gram-negative bacteria Escherichia coli (n = 6) and Klebsiella pneumoniae (n = 7) with a good zone of inhibition diameter, tested with the disc diffusion method. Based on these findings, it appears that A. indica AgNPs have promise as an antibacterial agent effective against MDR pathogens.     

An investigation of partial cone cracks in silicon nitride balls

Hybrid silicon nitride ball/steel raceway bearings are used in advanced aircraft engines and space propulsion systems. Silicon nitride is a brittle material and partial cone cracks, or c-cracks, originate from contact interactions during manufacturing. These cracks limit the Rolling Contact Fatigue (RCF) life of the balls. Here the authors examine subsurface Hertzian stresses between contacting spheres, using an analytical stress solution, to investigate their applicability to predicting and characterizing crack size and shape. The authors also incrementally develop these cracks through an iterative crack growth procedure using a 3D finite element analysis. Comparisons are then made to experimental images of the flaws in silicon nitride. By varying the initial conditions during the contact interaction of the balls we demonstrate that a wide range of cone and partial cone cracks, observed in practice, can be generated using both the analytical and numerical fracture mechanics approaches. Furthermore, an expression is presented for the impact velocity that induces a cone crack from a maximum radial stress criterion at the contact periphery.     

Reconstructing vector bundles on curves from their direct image on symmetric powers

Let C be an irreducible smooth complex projective curve, and let E be an algebraic vector bundle of rank r on C. Associated to E, there are vector bundles ${{\mathcal F}_n(E)}$ of rank nr on S ⁿ (C), where S ⁿ (C) is the n-th symmetric power of C. We prove the following: Let E ₁ and E ₂ be two semistable vector bundles on C, with genus ${(C)\, \geq\, 2}$ . If ${{\mathcal F}_n(E_1)\,\simeq \, {\mathcal F}_n(E_2)}$ for a fixed n, then ${E_1 \,\simeq\, E_2}$ .     

Synthesis of novel N-hydroxy heterocycles via intramolecular reductive cyclization of diketoximes by NaBH3CN

A simple and efficient protocol for the construction of substituted piperazines, piperidines, thiomorpholines, decahydroquinolines, perhydrocyclopenta[b]pyridine, and pyrrolidines bearing N-hydroxy substituents through intramolecular reductive cyclization of diketoximes using sodium cyanoborohydride is described.     

Stereoselective synthesis of 2-C-methylene glycosides and disaccharides via direct allylic substitution of hydroxy group in benzylated glycals

InCl₃ efficiently catalyzes allylic substitution of the hydroxy group of 2-C-hydroxymethyl glycals to afford a diversity of 2-C-methylene alkyl and aryl glycosides as well as disaccharides in high yields. This protocol surpasses the existing methods for the synthesis of 2-C-methylene glycosides as it obviates the need for functionalizing the allylic hydroxy group of glycals. The interest of this methodology relies on the extremely mild conditions required even with a free hydroxyl group at the allylic position of the glycals and that too only with a catalytic amount of InCl₃. The reaction is fast (30 min.), stereoselective and is compatible with a variety of oxygenated nucleophiles including those possessing acid-labile groups. A mechanistic investigation on the direct formation of an α,α-(1→1)linked disaccharide derivative from 2-C-hydroxymethyl galactal reveals that the reaction proceeds through a domino Ferrier rearrangement followed by a facile 1,3-alkoxy migration.