Chemical modification of coumarin dimer and HIV-1 integrase inhibitory activity

A systematic series of chemically modified coumarin dimmers has been synthesized and tested for their inhibitory activity against HIV-1 integrase. We observed that modified coumarin dimmers containing hydrophobic moiety on the linker display potent inhibitory activities.     

Recognizing a something when your library sees it

Advances are needed in random-display technologies to more tightly link drug actions and functions to the genes that control physiological processes. The reports discussed here explore two sides of these issues-generating new library formats and identifying the targets of drug ligands.     

Analysis of size-segregated aerosol-bound polycyclic aromatic hydrocarbons with high time resolution using two-step laser mass spectrometry

Polycyclic aromatic hydrocarbons are known for their mutagenic and carcinogenic properties. They are mainly emitted into the atmosphere by anthropogenic, incomplete combustion sources. Their trends over the course of a day are of interest in air quality management. A new combination of methods has been developed for the qualitative monitoring of polycyclic aromatic hydrocarbons in ambient aerosols with high time and size resolution. This has been accomplished by combining sampling with a rotating drum impactor and the analysis two-step laser mass spectrometry (L2MS). A validation for this method was carried out. Essential features of these combined techniques are (i) continuous, automatic sampling and (ii) selective as well as sensitive analysis due to the low detection limits which can be achieved with the L2MS analysis instrument. Analysis of a field sample taken in downtown Zurich, Switzerland, underlines the usefulness of this combined method, for example for following diurnal cycles of polycyclic aromatic hydrocarbons.     

The value of two-person zero-sum repeated games with lack of information on both sides

We consider repeated two-person zero-sum games in which each player has only partial information about a chance move that takes place at the beginning of the game. Under some conditions on the information pattern it is proved that \(\mathop {\lim }\limits_{n \to \infty } v_n\) exists,v _n being the value of the game withn repetitions. Two functional equations are given for which \(\mathop {\lim }\limits_{n \to \infty } v_n\) is the only simultaneous solutions. We also find the least upper bound for the error term \(\left| {v_n - \mathop {\lim }\limits_{n \to \infty } v_n } \right|\) .     

Modeling Very Oscillating Signals. Application to Image Processing

This article is a companion paper of a previous work where we have developed the numerical analysis of a variational model first introduced by Rudin et al. and revisited by Meyer for removing the noise and capturing textures in an image. The basic idea in this model is to decompose an image f into two components (u + v) and then to search for (u,v) as a minimizer of an energy functional. The first component u belongs to BV and contains geometrical information, while the second one v is sought in a space G which contains signals with large oscillations, i.e. noise and textures. In Meyer carried out his study in the whole ² and his approach is rather built on harmonic analysis tools. We place ourselves in the case of a bounded set of ² which is the proper setting for image processing and our approach is based upon functional analysis arguments. We define in this context the space G, give some of its properties, and then study in this continuous setting the energy functional which allows us to recover the components u and v. We present some numerical experiments to show the relevance of the model for image decomposition and for image denoising.     

Synthesis of new semi-rigid chelating agents for samarium-153

This study describes a simple, efficient synthesis pathway from trans-1,2-diaminocyclohexane that provides access to a new class of semi-rigid polyamine, polycarboxylic, and polyphosphonic ligands. The key steps in synthesis were the functionalisation (with an appropriate branching group) of a bisphosphonate diaminocyclohexane derivative and the introduction of methanephosphonic functions by a rarely used method.     

Structure Analysis of PVC Nanocomposites

In this paper poly(vinyl chloride)/clay nanocomposites were prepared by melt intercalation using a single screw extruder. Problems with thermal stability of these nanocomposites during compounding were largely eliminated by pre-treatment of the organoclay with plasticizer (dioctyl phthalate), which created a barrier between polymer and quaternary amine. These nanocomposite materials were analyzed with respect to their morphology. The intercalation, exfoliation, nano-phase dispersion and orientation were investigated using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). Moreover, different types of sample preparation for these techniques were tested as well. It was found that partially intercalated and disordered structure arose in poly (vinyl chloride) composites containing sodium type of montmorillonite, while a fine dispersion of partial to nearly full exfoliation of individual montmorillonite layers in poly (vinyl chloride) matrix was observed when this clay was organically modified. Finally, the influence of different mixing time (in extruder) on nano-phase morphology was surveyed.     

Single-crystal sapphire-fiber optic sensors based on surface plasmon resonance spectroscopy for in situ monitoring

Single-crystal sapphire-fiber optic sensors based on surface plasmon resonance (SPR) for refractive index (RI) measurements of aqueous and hydrothermal water solutions are described. Accurate measurement of RIs is essential to efficient operation and control of broad range of engineering processes. Some of these processes are carried out with harsh environments, such as high-temperature, high pressure, and chemical corrosion. These extreme physical conditions are proving a limiting factor in application of the conventional silica-based optical sensors. Single-crystal sapphire is an ideal material for sensor applications, where reliable performance is required in the extreme environment conditions. With regard to the liquid species detection, most applications of SPR sensors are designed to function near the refractive index of water (1.3330 RI). The RI changes of aqueous solution can be easily monitored by silica-fiber (RI, 1.4601 at 550 nm) based SPR sensor. However, the sapphire waveguide has a prohibitively high RI (1.7708 at 546 nm) for unmodified monitoring of the RI changes of aqueous solutions. For that purpose, a practical SPR probe geometry has been applied to the ability to tune the SPR coupling wavelength/angle pair with sapphire-fiber based SPR probe.     

Purification and characterization of acetate kinase from Clostridium thermocellum

Acetate kinase (EC 2.7.2.1), an enzyme involved in the wasteful production of acetate during conversion of cellulose to ethanol by Clostridium thermocellum, was purified 144-fold. The enzyme has an Mr of 84 kD by non-denaturing gradient gel electrophoresis, and an Mr of 46 kD when estimated with a denaturing gel; thus it appears to be a homodimer. Optimum enzyme activity occurs at 50°C and between pH 7.2 and 8.0. Acetate kinase is stable to temperatures up to 60°C, but is completely inactivated at 80°C after two h. The enzyme is stable between pH 7.0 and 9.0 when incubated at 50°C for two h. Optimum acetate kinase activity occurs at a MgCl₂:ATP ratio of 2:1, which indicates an interaction between Mg²⁺ and ATP and that between Mg²⁺ and acetate kinase. Enzyme activity is partially inhibited by KCl, an inorganic salt frequently used in chromatography and fermentation media, losing 60% activity in the presence of 0.2 M KCl. Sigmoidal enzyme kinetics were observed from the velocity plot of acetate kinase when either the acetate (S_0.5 = 285 mM) or ATP (S_0.5 = 11 mM) concentration was varied, suggesting cooperative binding of the two substrates.