Novel anti-Plasmodial hits identified by virtual screening of the ZINC database

Increased resistance of Plasmodium falciparum to most available drugs challenges the control of malaria. Studies with protease inhibitors have suggested important roles for the falcipain family of cysteine proteases. These enzymes act in concert with other proteases to hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. In order to find potential new antimalarial drugs, we screened in silico the ZINC database using two different protocols involving structure- and ligand-based methodologies. Our search identified 19 novel low micromolar inhibitors of cultured chloroquine resistant P. falciparum. The most active compound presented an IC₅₀ value of 0.5 μM against cultured parasites and it also inhibited the cysteine protease falcipain-2 (IC₅₀ = 25.5 μM). These results identify novel classes of antimalarials that are structurally different from those currently in use and which can be further derivatized to deliver leads suitable for optimisation.     

Cannabinoids in oral fluid by on-site immunoassay and by GC-MS using two different oral fluid collection devices

Oral fluid (OF) enables non-invasive sample collection for on-site drug testing, but performance of on-site tests with occasional and frequent smokers’ OF to identify cannabinoid intake requires further evaluation. Furthermore, as far as we are aware, no studies have evaluated differences between cannabinoid disposition among OF collection devices with authentic OF samples after controlled cannabis administration. Fourteen frequent (≥4 times per week) and 10 occasional (less than twice a week) adult cannabis smokers smoked one 6.8 % ?⁹-tetrahydrocannabinol (THC) cigarette ad libitum over 10 min. OF was collected with the StatSure Saliva Sampler, Oral-Eze, and Draeger DrugTest 5000 test cassette before and up to 30 h after cannabis smoking. Test cassettes were analyzed within 15 min and gas chromatography–mass spectrometry cannabinoid results were obtained within 24 h. Cannabinoid concentrations with the StatSure and Oral-Eze devices were compared and times of last cannabinoid detection (t _last) and DrugTest 5000 test performance were assessed for different cannabinoid cutoffs. 11-nor-9-Carboxy-THC (THCCOOH) and cannabinol concentrations were significantly higher in Oral-Eze samples than in Stat-Sure samples. DrugTest 5000 t _last for a positive cannabinoid test were median (range) 12 h (4–24 h) and 21 h (1–?≥?30 h) for occasional and frequent smokers, respectively. Detection windows in screening and confirmatory tests were usually shorter for occasional than for frequent smokers, especially when including THCCOOH ≥20 ng L^?1 in confirmation criteria. No differences in t _last were observed between collection devices, except for THC ≥2 μg L^?1. We thus report significantly different THCCOOH and cannabinol, but not THC, concentrations between OF collection devices, which may affect OF data interpretation. The DrugTest 5000 on-site device had high diagnostic sensitivity, specificity, and efficiency for cannabinoids.     

Electromagnetic wormholes and virtual magnetic monopoles from metamaterials

We describe new configurations of electromagnetic (EM) material parameters, the electric permittivity epsilon and magnetic permeability micro, which allow one to construct devices that function as invisible tunnels. These allow EM wave propagation between the regions at the two ends of a tunnel, but the tunnels themselves and the regions they enclose are not detectable to lateral EM observations. Such devices act as wormholes with respect to Maxwell's equations and effectively change the topology of space vis-à-vis EM wave propagation. We suggest several applications, including devices behaving as virtual magnetic monopoles, invisible cables, and scopes for MRI-assisted surgery.     

Narrowband, tunable, frequency-doubled, erbium-doped fiber-amplifed transmitter

We report on the development of a fiber-based laser transmitter designed for active remote sensing spectroscopy. The transmitter uses a master oscillator power amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled potassium titanium oxide phosphate crystal. With 35 W of single-frequency peak optical pump power, 8 W of frequency-doubled peak power was achieved. The utility of this single-frequency, wavelength tunable, power scalable laser was then demonstrated in a spectroscopic measurement of diatomic oxygen A band.     

Improving the Yield and Rate of Acid-Catalyzed Deconstruction of Lignin by Mechanochemical Activation

Lignin is a potential biomass feedstock from plant material, but it is particularly difficult to economically process. Inspired by recent ball-milling results, state-of-the-art quantum mechanochemistry calculations have been performed to isolate and probe the purely mechanochemical stretching effect alone upon acid-catalyzed deconstruction of lignin. Effects upon cleavage of several exemplary simple ethers are examined first, and with low stretching force they all are predicted to cleave substantially faster, allowing for use of milder acids and lower temperatures. Effects upon an experimentally known lignin fragment model (containing the ubiquitous β-O-4 linkage) are next examined; this first required a mechanism refinement (3-step indirect cleavage, 1-step side reaction) and identification of the rate-limiting step under zero-force (thermal) conditions. Mechanochemical activation using very low stretching forces improves at first only yield, by fully shutting off the ring-closure side reaction. At only somewhat larger forces, in stark contrast, a switch in mechanism is found to occur, from 3-step indirect cleavage to the direct cleavage mechanism of simple ethers, finally strongly enhancing the cleavage rate of lignin. It is concluded that mechanochemical activation of the common β-O-4 link in lignin would improve the rate of its acidolysis via a mechanism switch past a low force threshold. Relevance to ball-milling experiments is discussed.     

β-secretase 1 inhibitory activity and AMP-activated protein kinase activation of Callyspongia samarensis extracts

Abstract

The methanolic extract of Callyspongia samarensis (MCS) significantly inhibited β-secretase 1 (IC₅₀ 99.82?µg/mL) in a dose-dependent manner and demonstrated a noncompetitive type of inhibition. Furthermore, it exhibited the highest AMPK activation (EC₅₀ 14.47?μg/mL) as compared with the standard, Aspirin (EC₅₀ >100?μg/mL). HPLC/ESI-MS analysis of MCS extract revealed 15 peaks, in which nine peaks demonstrated similar fragmentation pattern with the known compounds in literature and in database library: 5-aminopentanoic acid (1), 4-aminobutanoic acid (3), Luotonin A (4), (E)-3-(1H-imidazol-5-yl) prop-2-enoic acid (8), Galactosphingosine (10), D-sphingosine (11), 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone (12), hydroxydihydrovolide (13), and 3,5-dibromo-4-methoxyphenylpyruvic acid (14); and 6 peaks are not identified (2, 5–7, 9, and 15). Acute oral toxicity test of MCS extract revealed that it is nontoxic, with an LD₅₀ of >2000?mg/kg. Assessment of BBB permeability of MCS extract showed that compound 15 was able to cross the BBB making it a suitable candidate for developing CNS drugs.     

Novel poly(aryl ether phthalazinium) ionomers and their properties

The synthesis of N-phenyl phthalazinium salts by condensation of a 1,2-diaroylbenzene with phenylhydrazine is described. This reaction was utilized to prepare novel poly(aryl ether phthalazinium) ionomers by the direct condensation of poly(aryl ether ketone)s with phenylhydrazine. The preparation of poly(aryl ether phthalazinium) ionomers by methylation of poly(aryl ether phthalazine)s is also described. Most of the ionomers are amorphous, thermally stable, and soluble in organic solvents. They can be cast into flexible and strong films. The glass transition temperature of the ionomers ranges from 297 to 363°C, an increase of 12 to 100°C over the corresponding neutral polymers. © 1996 John Wiley & Sons, Inc.     

Ring-opening polymerization of macrocyclic aryl ether ketone oligomers containing the 1,2-dibenzoylbenzene moiety

Facile ring-opening polymerization of cyclic aryl ether oligomers containing the 1,2-dibenzoylbenzene moiety to form high molecular weight linear polymers in the presence of a nucleophilic initiator is described. The polymerization can be initiated in the melt in the presence of a nucleophilic initiator such as potassium carbonate, cesium fluoride, and alkali phenoxides. Various alkali phenoxides were investigated as potential nucleophilic initiators. The polymerization reaction rate in the melt increases in the order of K⁺ > Na⁺ > Cs⁺, and in the order of ⁻OPhPhO⁻ > PhO⁻ > PhOPhO⁻ > PhPhO⁻. However, the polymerization in an aprotic dipolar solvent is faster in the presence of cesium phenoxide than in the presence of potassium phenoxide. Polymerization of the cyclic oligomers in solution demonstrates that the ring-opening polymerization proceeds via a chain-growth mechanism and involves a transetherification reaction between linear and cyclic aryl ether oligomers. The ring-chain equilibrium is much more favorable towards linear polymers. Since little or no ring strain exists in the cyclic system, the transetherification reactions are indiscriminate with regards to cyclic or linear chains and the interchain equilibration is also a facile process during polymerization. This intermolecular transetherification has been demonstrated by using low molecular weight aryl ethers to control the molecular weight of the polymer formed via ring-opening polymerization. © 1996 John Wiley & Sons, Inc.     

Investigation of the mechanism of reaction of S-ethyl-N,N′-tetraethyldiamidothio-phosphite with [C5H 5Mn(CO)2NO]+BF by fourier transform infrared spectroscopy

FT-IR spectroscopy and a special mathematical program were used for the real-time monitoring of the mechanistic path of the reaction of S-ethyl-N,N-tetraethyldiamidothiophosphite with [CpMn(CO)-₂NO]⁺BFequation/tex2gif-stack-3.gif. The formation of a few intermediates is described.     

“intelligent” polymers in medicine and biotechnology

One can define “intelligent” polymers as those polymers which respond with large property changes to small physical or chemical stimuli. These polymers may be in various forms, such as in solution, on surfaces, or as solids. One may also combine “intelligent” aqueous polymer systems with biomolecules, to yield a large family of polymers which respond “intelligently” to physical, chemical or biological stimuli. This article overviews such interesting and versatile polymer systems.