Design and Synthesis of Fluorescent Acyclic Nucleoside Phosphonates as Potent Inhibitors of Bacterial Adenylate Cyclases

Bordetella pertussis adenylate cyclase toxin (ACT) and Bacillus anthracis edema factor (EF) are key virulence factors with adenylate cyclase (AC) activity that substantially contribute to the pathogenesis of whooping cough and anthrax, respectively. There is an urgent need to develop potent and selective inhibitors of bacterial ACs with prospects for the development of potential antibacterial therapeutics and to study their molecular interactions with the target enzymes. Novel fluorescent 5‐chloroanthraniloyl‐substituted acyclic nucleoside phosphonates (Cl‐ANT‐ANPs) were designed and synthesized in the form of their diphosphates (Cl‐ANT‐ANPpp) as competitive ACT and EF inhibitors with sub‐micromolar potency (IC₅₀ values: 11–622 nm ). Fluorescence experiments indicated that Cl‐ANT‐ANPpp analogues bind to the ACT active site, and docking studies suggested that the Cl‐ANT group interacts with Phe306 and Leu60. Interestingly, the increase in direct fluorescence with Cl‐ANT‐ANPpp having an ester linker was strictly calmodulin (CaM)‐dependent, whereas Cl‐ANT‐ANPpp analogues with an amide linker, upon binding to ACT, increased the fluorescence even in the absence of CaM. Such a dependence of binding on structural modification could be exploited in the future design of potent inhibitors of bacterial ACs. Furthermore, one Cl‐ANT‐ANP in the form of a bisamidate prodrug was able to inhibit B. pertussis ACT activity in macrophage cells with IC₅₀=12 μm .     

Fermi Level Control of Point Defects During Growth of Mg-Doped GaN

In this study, Fermi level control of point defects during metalorganic chemical vapor deposition (MOCVD) of Mg-doped GaN has been demonstrated by above-bandgap illumination. Resistivity and photoluminescence (PL) measurements are used to investigate the Mg dopant activation of samples with Mg concentration of 2 × 10¹⁹ cm^?3 grown with and without exposure to ultraviolet (UV) illumination. Samples grown under UV illumination have five orders of magnitude lower resistivity values compared with typical unannealed GaN:Mg samples. The PL spectra of samples grown with UV exposure are similar to the spectra of those grown without UV exposure that were subsequently annealed, indicating a different incorporation of compensating defects during growth. Based on PL and resistivity measurements we show that Fermi level control of point defects during growth of III-nitrides is feasible.     

Characterization of Threading Dislocations in PVT-Grown AlN Substrates via x-Ray Topography and Ray Tracing Simulation

Threading dislocations in aluminum nitride boules grown by physical vapor transport method were systematically studied via synchrotron x-ray topography (white beam and monochromatic) in conjunction with ray tracing simulations. Two major types of threading dislocations were observed in the c-axis-grown boules: threading screw dislocations (TSDs) and threading edge dislocations (TEDs) with Burgers vectors along the [0001] and $\langle 11\bar{2}0 \rangle $ directions, respectively. TSDs were typically observed in the middle of the boule while TEDs were commonly observed to aggregate into arrays along the $ \langle 1\bar{1}00 \rangle $ and $ \langle 11\bar{2}0 \rangle $ directions in various parts of the boule on basal plane oriented wafers. By comparison with ray tracing simulations, the absolute Burgers vectors of both TSDs and TEDs in the arrays could be unambiguously determined. TEDs comprise over 90 % of all threading dislocations observed. The relationships between TED arrays and low angle grain boundaries and their possible formation mechanisms are discussed.     

New Insights into the Setting Processes of Glass Ionomer Cements from Analysis of Dielectric Properties

The setting processes in the commercial glass ionomer cement (Fuji IX Fast) and resin modified glass ionomer cement (Fuji II LC) were investigated by the dielectric spectroscopy. The changes in the real and imaginary parts of the dielectric permittivity [ε*(ω)] as well as dielectric loss (tan δ) with time for Fuji IX Fast show several distinct regions which are related to the different stages of the acid–base reaction. Interestingly, the first stage that lasts for approximately 12 min terminates with a sharp decrease in dielectric parameters which is most probably related to the instantaneous (micro)fracturing of the sample due to a rapid build–up of the shrinkage stress. On the other hand, evolution of the dielectric properties during the setting of Fuji II LC indicates fast reaction in the initial stage (within few minutes) followed by the slow gradual change as a result of the competing nature of the acid–base reaction and light‐activated polymerization.     

Changes of properties of cured and uncured disiloxane bisbenzocyclobutene thin films under irradiation

The effects induced by α-particles and laser beam irradiation in air atmosphere in uncured and cured bisbenzocyclobutene (BCB) 2 μm thick films, spin-coated on glass/ITO surface have been investigated. α-Particle irradiation was done by means of a thin film ²⁴¹Am source (E_α = 5.486 MeV), up to the total fluence of about 5 × 10¹⁰ particles/cm². Laser irradiation was performed by a Nd³⁺:YAG (λ = 1.06 μm) laser in the free generation and the Q-switch regime, using both focused and unfocused beams. Irradiation induced changes were investigated using Light and Atomic Force Microscopy (AFM), infrared (IR), Ultraviolet/visible (UV/vis) and Raman spectroscopy by inspecting several uncured and cured BCB films before and after irradiation. It has been found that both types of irradiation under investigated conditions have produced a novel phase in the material, which is not present either in the uncured or the cured BCB films. Possible implications of the observed effects on curing and degradation of BCB films have been discussed.     

Efficient and novel Sb2S3 based solar cells with chitosan/poly(ethylene glycol)/electrolyte blend

We present here a novel solar cell made of ITO/composite p‐doped Sb₂S₃ + P3HT + PANI+TiO₂/amorphous Sb₂S₃ + P3HT + PANI + TiO₂/n‐doped Sb₂S₃ + P3HT + PANI + TiO₂/solid carrier/aluminum as counter electrode. With spraying technique, the layers were deposited and the thickness of films was 1 μm. A new solid carrier of electrolyte was a blend consisted of chitosan (low MW), polyethylene glycol and electrolyte. X‐ray diffraction was recorded to confirm the amorphous nature of the blend. Information about the surface appearance and roughness of a solid carrier dry and soaked in the electrolyte was given by atomic force microscopy. The solar cell was examined at very low and low light intensity (5% and 35% of sun, respectively), and at standard test conditions (100% of sun) using different light sources. The whole cell surface was 7.5 cm² while the illuminated part was 3 cm². Obtained results expressed for the illuminated surface showed the highest efficiency of 23.1% at 5% of sun while the efficiency of the cell was 2.9% at 35% of sun and only 0.75% at intensity of 100% of sun.     

Void fraction distribution in a bisectional bubble column reactor

This article presents the distribution of the local void fraction (α) in a mock-up bisectional bubble column with a diameter of 0.63 m. Owing to the lack of such data in the literature, α was investigated experimentally using a microresistivity (R) probe and a phase discrimination procedure based on the probe signal. The two-phase mixture that consisted of air and tap water was measured at 342 nodes in the vertical half-section plane of the column. Relatively small differences between the volume-integrated local values of α and the measured total gas holdups showed reasonably good agreement under all conditions. Experimental data were used for validation of a bubble column numerical model for a low hydrodynamic regime with commercial computational fluid dynamics (CFD) code. The difference between the CFD calculated total gas holdup and the experimentally measured mean value is 8.8%, while some differences in the local void fraction distributions were found in the lower part of the column. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1186–1197, 2019     

Refined fourier-transform method of analysis of full two-dimensional digitized interferograms

A refined Fourier-transform method of analysis of interference patterns is presented. The refinements include a method of automatic background subtraction and a way of treating the problem of heterodyning. The method proves particularly useful for analysis of long sequences of interferograms.