Synthesis of 3′‐Fluoro‐tRNA Analogues for Exploring Non‐ribosomal Peptide Synthesis in Bacteria

Aminoacyl‐tRNAs (aa‐tRNAs) participate in a vast repertoire of metabolic pathways, including the synthesis of the peptidoglycan network in the cell walls of bacterial pathogens. Synthesis of aminoacyl‐tRNA analogues is critical for further understanding the mechanisms of these reactions. Here we report the semi‐synthesis of 3′‐fluoro analogues of Ala‐tRNA^Ala. The presence of fluorine in the 3′‐position blocks Ala at the 2′‐position by preventing spontaneous migration of the residue between positions 2′ and 3′. NMR analyses showed that substitution of the 3′‐hydroxy group by fluorine in the ribo configuration favours the S‐type conformation of the furanose ring of terminal adenosine A76. In contrast, the N‐type conformation is favoured by the presence of fluorine in the xylo configuration. Thus, introduction of fluorine in the ribo and xylo configurations affects the conformation of the furanose ring in reciprocal ways. These compounds should provide insight into substrate recognition by Fem transferases and the Ala‐tRNA synthetases.     

Alignment of Rod‐Shaped Single‐Photon Emitters Driven by Line Defects in Liquid Crystals

Arrays of liquid crystal defects—linear smectic dislocations—are used to trap semiconductor CdSe/CdS dot‐in‐rods which behave as single‐photon emitters. Measurements of the emission diagram are combined together with measurements of the emitted polarization of the single emitters. It is shown that the dot‐in‐rods are confined parallel to the linear defects to allow for a minimization of the disorder energy associated with the dislocation cores. It is demonstrated that the electric dipoles associated with the dot‐in‐rods, tilted with respect to the rods, remain oriented in the plane including the smectic linear defects and perpendicular to the substrate, most likely due to dipole/dipole interactions between the dipoles of the liquid crystal molecules and those of the dot‐in‐rods. Using smectic dislocations, nanorods can consequently be oriented along a unique direction for a given substrate, independently of the ligands' nature, without any induced aggregation, leading as well to a fixed azimuthal orientation for the dot‐in‐rods' dipoles. These results open the way for the fine control of nanoparticle anisotropic optical properties, in particular, fine control of single‐photon emission polarization.     

1‐(1H‐Indol‐3‐yl)ethanamine Derivatives as Potent Staphylococcus aureus NorA Efflux Pump Inhibitors

The synthesis of 37 1‐(1H‐indol‐3‐yl)ethanamine derivatives, including 12 new compounds, was achieved through a series of simple and efficient chemical modifications. These indole derivatives displayed modest or no intrinsic anti‐staphylococcal activity. By contrast, several of the compounds restored, in a concentration‐dependent manner, the antibacterial activity of ciprofloxacin against Staphylococcus aureus strains that were resistant to fluoroquinolones due to overexpression of the NorA efflux pump. Structure–activity relationships studies revealed that the indolic aldonitrones halogenated at position 5 of the indole core were the most efficient inhibitors of the S. aureus NorA efflux pump. Among the compounds, (Z)‐N‐benzylidene‐2‐(tert‐butoxycarbonylamino)‐1‐(5‐iodo‐1H‐indol‐3‐yl)ethanamine oxide led to a fourfold decrease of the ciprofloxacin minimum inhibitory concentration against the SA‐1199B strain when used at a concentration of 0.5 mg L ^?1. To the best of our knowledge, this activity is the highest reported to date for an indolic NorA inhibitor. In addition, a new antibacterial compound, tert‐butyl (2‐(3‐hydroxyureido)‐2‐(1H‐indol‐3‐yl)ethyl)carbamate, which is not toxic for human cells, was also found.     

Importance of the structure of paper support in gas transfer properties of protein‐coated paper

Composite materials made from fibrous support coated with agro‐polymers are widely commercialized for different applications. But, their transfer properties have only been sparingly studied despite their importance in membrane technologies or food packaging. Furthermore, most of past studies on the topic have been focused on the impact of surface properties of the support on the final coated material structure and its properties; leaving unexplored the potential impact of the in‐bulk structure of the support. This study demonstrated the influence of in‐bulk structure and especially fibers refining degree of 4 kraft papers (SP28, 36, 60, and 80) on the structure, and surface and gas transfer properties of their respective wheat gluten (WG) coated papers (WGP28, 36, 60, and 80). Paper presenting a high fibers refining degree (SP28) exhibited very tight and narrow in bulk fibers network which prevented most of the WG‐coated layer penetration, maintaining an important WG apparent layer on top of the paper and a small fibers/wheat gluten composite zone inside (WGP28). Such structure gave strong “WG‐like” properties to the final coated material with moderate oxygen permeation and high permselectivity (1.50 × 10^?11 mol m^?2 s^?1 Pa^?1 and 8.09, respectively for WGP28) whereas the highly impregnated structure of coated papers built on lowly refined papers (SP80, with wide and loose structure) gave coated materials presenting weak “WG‐like” properties, supposedly due to a thick composite zone presenting interfacial defects, with higher oxygen permeation and very limited permselectivity (11.90 × 10^?11 mol m^?2 s^?1 Pa^?1 and 1.06, respectively for WGP80). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2848–2858, 2013     

Characterisation of genuine and derived cranberry proanthocyanidins by LC–ESI-MS

Cranberry proanthocyanidins (PACs) were characterised by HPLC (after thiolysis) and LC–ESI-MS analysis after fractionation by normal-phase chromatography. According to the HPLC retention time and mass spectra of compounds released after depolymerisation reaction, PACs are based on epicatechin and dimer A2 units along with catechin (minor component) and epigallocatechin (trace amounts). Fractionation at semi-preparative scale on normal phase allowed to remove other phenolic compounds than PACs (flavonols, phenolic acids and anthocyanins) and to separate the PACs according to their polymerisation degrees. Six fractions were eluted. PAC concentration, mean degree of polymerisation and percentage of A-type bonds were calculated for these six fractions by HPLC after thiolysis. Whereas the three first fractions contained phenolic acids and flavonols, the three latest fractions were enriched in PACs. Genuine PACs (A and B-types) from DP2 to DP16 were detected by LC–DAD-ESI-MS analysis. Fragmentation on ion trap spectrometer allowed us to determine the position of A-type bonds. Derived PACs were also observed: anthocyanin ethyl-bridged PACs (monomer to tetramer) in the three last fractions, flavonol-ethyl-PACs (monomer and dimer) in the third fraction and pyranoanthocyanin derivatives in the last fraction.     

Capture and corruption in public utilities: The cases of water and electricity in Sub-Saharan Africa

The paper focuses on public utilities services located in poor countries with a special attention to capture and corruption issues. It confronts the optimal policy of Auriol and Picard [Privatization in Developing Countries and the Government Budget Constraint, Nota di Lavoro 75.2002. Fondazione Eni Enrico Mattei, Milan, Italy] regarding private sector involvement in public utilities with empirical evidence on water and electricity in Sub-Saharan Africa (SSA). As predicted by the theory, the participation of private unregulated firms in the supply of services for the middle class and poor people is fairly common in SSA. By contrast, services for rich people are provided by public utilities. Theory suggests that their prices should be high so that the public firms make a profit. Yet piped water and electricity are subsidized. This suggests that there is a problem of capture by the ruling elite. Since ruling elites design privatization programs, there is concern about their optimality. The paper shows that the social cost of corrupted privatization is non-monotone in the opportunity cost of public funds. Because of the fiscal loss it represents, privatizing profit centers of public firms entails huge social costs in very poor countries.     

Assessment of potential slope failure sites at Mt. Can-abag, Guinsaugon, Philippines, based on stratigraphy and rock strength

Geological mapping was undertaken to determine the stratigraphy and potential landslide sites along Mt. Can-abag in St. Bernard, Philippines, where a disastrous landslide occurred in February 2006. The area is underlain by a sequence of NW- to SW-dipping breccias, sandstones and mudstones, with andesite intrusions. The low permeability of the mudstones, which form an aquiclude and hence confined aquifers, results in the build-up of pore pressures. Although the strata dip into the hillside, the fault-created discontinuities mean that the NE-facing slope of Mt. Can-abag is prone to wedge failures.     

Possibilities and Limits of Application of Electrical Resistance Tomography in Hydrodynamics of Bubble Columns

Knowing the hydrodynamic regime in which is working a bubble column is of great importance because the regime affects strongly the mass transfer between the phases. To this end, we examine the potentialities of an Electrical Resistance Tomography (ERT) device. We analyse cross correlation of electrode pair measurements, of neighbouring pixels and power spectra of averaged pixels within a single plane as well as cross correlations of averaged pixels between two planes, without finding a clear signature of the churn turbulent flow. Variable gas flow rate inputs are used to determine the time resolution of the ERT.     

Light induced degradation of testosterone in waters

The degradation of testosterone under simulated irradiations was studied in phosphate buffers and in natural waters at various excitation wavelengths. The quantum yield of photolysis was significantly lower at 313 nm (2.4 × 10^− 3) than at 254 nm (0.225). The formation of several photoproducts was observed, some of them being rapidly transformed in turn while others show higher stability towards subsequent irradiations. The nature of the main products was tentatively identified, both deduced from their spectral and spectrometric data and by comparison with synthesised standard compounds. Among the obtained photoproducts, the main one is possibly a spiro-compound, hydroxylated derivative of testosterone originating from the photohydratation of the enone group. The photodegradation pathway includes also photorearrangements. One of them leads to (1,5,10)-cyclopropyl-17β-hydroxyandrostane-2-one. The pH of the water does not seem to affect the rate of phototransformation and the nature of the by-products.