2,4-Diamino-5-(2'-arylpropargyl)pyrimidine derivatives as new nonclassical antifolates for human dihydrofolate reductase inhibition

Dihydrofolate reductase (DHFR) has been a well-recognized target for the development of therapeutics for human cancers for several decades. Classical inhibitors of DHFR use an active transport mechanism to gain access to the cell; disabling this mechanism creates a pathway for resistance. In response, recent research focuses on nonclassical lipid-soluble DHFR inhibitors that are designed to passively diffuse through the membrane. Here, a new series of propargyl-linked antifolates are investigated as potential nonclassical human DHFR inhibitors. Several of these compounds exhibit potent enzyme inhibition with 50% inhibition concentration values under 500 nM. Molecular docking investigations show that the compounds maintain conserved hydrogen bonds between the pyrimidine ring and the enzyme as well as form van der Waals interactions with critical residues in the active site. Interestingly, the most potent compound, 2,4-diamino-5-(3-(3,4,5-trimethoxyphenyl)prop-1-ynyl)-6-ethylpyrimidine (compound 35), is 3500-fold more potent than trimethoprim, a potent inhibitor of bacterial DHFR but weak inhibitor of human DHFR. The two structural differences between compound 35 and trimethoprim show that the propargyl linkage and the substitution at C6 of the pyrimidine ring are critical to the formation of contacts with Thr 56, Ser 59, Ile 60, Leu 22, Phe 31 and Phe 34 and hence, to enhancing potency. The propargyl-linked antifolates are efficient ligands with a high ratio of potency to the number of non-hydrogen atoms and represent a potentially fruitful avenue for future development of antineoplastic agents.     

Enzymatic polymerization of polythiophene by immobilized glucose oxidase

In this study ‘green’, environmentally friendly enzymatic reaction-based synthesis of conducting polymer polythiophene (PTP) is proposed. Glucose oxidase (GO_x) was shown as an effective catalyst, which, in the presence of glucose, produces hydrogen peroxide suitable for the oxidative polymerization of PTP under ambient conditions at neutral pH. Enzymatically induced formation of the PTP layer over GO_x-modified graphite rod electrode (GRE) was demonstrated and evaluated amperometrically and by attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy. Surface morphology of GO_x- and PTP-modified GR electrodes was characterized by atomic force microscopy. It was clearly shown that the apparent kinetic Michaelis constant (K_M(app.)) of GO_x/PTP-modified GRE increased by increasing the duration of polymerization reaction. Therefore, enzymatic polymerization could be applied in adjustment and/or tuning of K_M(app.) and other kinetic parameters of GO_x-based electrodes used in biosensor design.     

Effect of Ultrasonic Irradiation on the Treatment of Poly-Aromatic Substances (PAHs) from a Petrochemical Industry Wastewater

The effects of sonication time, nitrogen, N₂(g), increasing temperature, dissolved oxygen (DO) and titanium dioxide (TiO₂) concentrations on the sonodegradation of polyaromatic hydrocarbons (PAHs) in petrochemical wastewaters were investigated. Sonication alone without N₂(g), DO and TiO₂ provided 80% maximum PAH yields at 2 5°C after 150 min. This PAH yield increased to 89–95% at 60 °C after 150 min sonication. The contribution of DO, N₂(g) and TiO₂ on the PAH removal was not significant compared to the control. In the presence of HCO₃ ^?, the degradation of hydrophobic PAH dibenz[a,h]anthracene (DahA)was suppressed in the acceleration step of the sonication. Maximum acute toxicity removal was reached by 30 min N₂(g) sparging, 4 mg/L DO and by 0.1 mg/L TiO₂ after 150 min sonication.     

Recovery of metals from complexed solutions by electrodeposition

Electrolytic recovery of metals from aqueous solutions containing complexing chelating agents such as EDTA, NTA, and citrate was studied in a two-chamber cell separating with a commercial cation-exchange membrane (CEM). Equimolar solutions of metal and a chelating agent as a catholyte and NaNO₃ as an anolyte were used; the effect of current densities, initial catholyte and anolyte pH, metal concentration and the type of the CEM, chelating agent and metal on the recovery of metals was determined. The recovery of metal increased with higher initial anolyte pH, concentration and current density, whereas it decreased with lower initial catholyte pH. The results show that electrodeposition seems to be an applicable method for the recovery of metals under appropriate conditions.     

Node pacing for small optical RAM-buffered packet-switching networks

One of the difficulties with optical packet switched (OPS) networks is buffering optical packets in the network. The only available solution that can currently be used for buffering in the optical domain is using long fiber lines called fiber delay lines (FDLs), which have severe limitations. Moreover, the research on optical RAM presently being done is not expected to achieve a large capacity soon. However, the burstiness of Internet traffic causes high packet drop rates and low utilization in very small buffered OPS networks. We therefore propose a new node-based pacing algorithm for decreasing burstiness. We show that by applying some simple pacing at the edge or core backbone nodes, the performance of very small optical RAM buffered core OPS networks with variable-length packets can be notably increased.     

Effect of operating parameters on color and COD removal performance of SBR: sludge age and initial dyestuff concentration

Effect of sludge and initial dyestuff concentration on color and COD removal performance of anaerobic-aerobic sequential batch reactor was investigated. Remazol Red RR a vinylsulphonyl (VS) and monochlortriazine (MCT), reactive azo dye was used in the study. Sludge age was varied between thetaC=12 days and thetaC=30 days and dyestuff concentration was between D0=50 and D0=500 mg l(-1). The maximum color and COD removal was obtained as 95% and 70% for D0=60 mg l(-1) and COD0=800 mg l(-1) at 15 days sludge retention time, respectively, and no further improvement was observed when sludge age was increased to 30 days. The main color removal phase in this operation system was the anaerobic phase. Because, the color removal efficiency was already above 95% under anaerobic condition and therefore, the contribution of aerobic phase to color removal was negligible. Increasing dyestuff concentration did not significantly affect the decolorization. It was possible to obtain over 90% dyestuff removal even at D0=500 mg l(-1). SBR system reduces 1000 mg l(-1) initial COD concentrations to about 400 mg l(-1) for dyestuff concentration up to 150 mg l(-1). COD removal efficiency decreased from 70% to 60% by increasing initial dyestuff concentration from 100 to 500 mg l(-1). The results indicated that dyestuff and COD are mainly used by anaerobic organisms and aeration does not improve the performance of SBR system.     

Determining the Effective Constitutive Parameters of Finite Periodic Structures: Photonic Crystals and Metamaterials

A novel approach to find the effective electric and magnetic parameters of finite periodic structures is proposed. The method uses the reflection coefficients at the interface between a homogenous half-space and the periodic structure of different thicknesses. The reflection data are then approximated by complex exponentials, from which one can deduce the wavenumber, and the effective electric and magnetic properties of the equivalent structure by a simple comparison to the geometrical series representation of the generalized reflection from a homogenous slab. Since the effective parameters are for the homogenous equivalent of the periodic structure, the results obtained are expected to be independent of the number of unit cells used in the longitudinal direction. Although the proposed method is quite versatile and applicable to any finite periodic structure, photonic crystals and metamaterials with metallic inclusions have been used to demonstrate the application of the method in this paper.     

Stability of two-layered fluid flows in an inclined channel

A linear stability analysis of two-layer fluid flows in an inclined channel geometry has been carried out. The onset of flow transitions and the spatio-temporal characteristics of secondary flows produced by the flow instabilities have been examined. The effects of density and viscosity stratifications and surface tension on flow structures also have been investigated at various values of Froude numbers (channel inclinations). Multi-domain Chebyshev–Tau spectral methods along with MATLAB QZ eigenvalue solver are used to determine the whole spectrum of the eigenvalues and associated eigenfunctions. The neutral stability diagrams and stability boundaries are constructed for various values of flow parameters. The onset of flow transitions and flow structures predicted by linear stability analysis are compared against experimental results and they agree reasonably well. The results presented in the present paper imply that the shear mode of flow transitions is the one likely to be identified in experiments.     

Combined buoyancy and viscous effects in liquid–liquid flows in a vertical pipe

This paper presents experimental and numerical results of interfacial dynamics of liquid–liquid flows when an immiscible core liquid is introduced into a continuous liquid flow. The fully developed flow model predicts multiple solutions of the jet diameter over a range of dimensionless numbers: flow rate ratio, viscosity ratio, Bond and Capillary numbers. Experiments have been carried out using Polyethylene Glycol (PEG) and Canola oil to investigate the realizability of the three possible solutions predicted by the fully developed flow model. The measured values of inner fluid radii agree very well with the lower branch of the three branched solution while deviating from the top branch beyond a critical flow ratio value. This deviation is attributed to the fact that the flow develops a non-axisymmetric solution at this critical point. Computational fluid dynamics simulations have also been performed to examine the developing core annular flow and to compare the analytical solution results of liquid jet radius. The results predicted by numerical simulations agree very well with both the lower and upper branches of solution predicted by the analytical theory.     

Containment capsule stresses for encapsulated phase change materials

The encapsulation of a phase change material to store thermal energy is considered here for concentrated solar power systems. The stress distribution in a spherical nickel shell of 250 μ thickness formed around a ball of zinc by the electroless deposition process and a stainless steel cylindrical shell containing zinc are considered. The effect of external forces and imperfections within the shell structure that could affect the deformation are also modeled. The aim of the simulations performed is to establish a suitable thickness for the encapsulating material. It is concluded that while the shell can deform and safely withstand the anticipated expansion of the zinc, the added effects from point loads caused by the weight of the surrounding encapsulated capsules and other possible imperfections in the capsule structure could cause failure. A three-dimensional finite element model is used to establish the stresses in cylinders of different aspect ratio caused by the expansion of zinc as it melts inside of the encapsulation. The amount of void space that must be left inside of the capsule, so that the expansion of the zinc during phase change and the increase in gas pressure inside of the vessel will not cause failure of the shell, is determined from simulations. Results indicate that the cylinder with welded ends could easily contain up to 86% of the initial volume full of zinc with only a very small amount of plastic deformation, less than 0.5% strain, corresponding to an internal pressure of 2.03 MPa.