Self-assembling catalytic systems based on new amphiphile containing purine fragment,exhibiting substrate specificity in hydrolysis of phosphorus acids esters

Micellar catalytic systems based on new purine-containing amphiphile for hydrolytic decomposition of organophosphorus toxicants have been prepared. The aggregation threshold of the system has been estimated by means of tensiometry, conductometry, spectrophotometry, and dynamic light scattering. The solubilizing action of the amphiphile towards the hydrophobic dye has been demonstrated. Kinetic studies of hydrolysis of phosphonates differing in the hydrophobicity have disclosed the substrate specificity of the micellar catalysts; inhibition instead of catalysis has been observed in the case of the less hydrophobic substrate.     

Inverse Radon Transform at Work

Physics of Particles and Nuclei Letters - The inverse Radon transform allows to obtain partonic double distributions from (extended) generalized parton distributions. We express the extension of...     

Polymer–Colloid Complexes Based on Cationic Imidazolium Amphiphile,Polyacrylic Acid and DNA Decamer

The solution behavior and physicochemical characteristics of polymer–colloid complexes based on cationic imidazolium amphiphile with a dodecyl tail (IA-12) and polyacrylic acid (PAA) or DNA decamer (oligonucleotide) were evaluated using tensiometry, conductometry, dynamic and electrophoretic light scattering and fluorescent spectroscopy and microscopy. It has been established that PAA addition to the surfactant system resulted in a ca. 200-fold decrease in the aggregation threshold of IA-12, with the hydrodynamic diameter of complexes ranging within 100–150 nm. Electrostatic forces are assumed to be the main driving force in the formation of IA-12/PAA complexes. Factors influencing the efficacy of the complexation of IA-12 with oligonucleotide were determined. The nonconventional mode of binding with the involvement of hydrophobic interactions and the intercalation mechanism is probably responsible for the IA-12/oligonucleotide complexation, and a minor contribution of electrostatic forces occurred. The latter was supported by zeta potential measurements and the gel electrophoresis technique, which demonstrated the low degree of charge neutralization of the complexes. Importantly, cellular uptake of the IA-12/oligonucleotide complex was confirmed by fluorescence microscopy and flow cytometry data on the example of M-HeLa cells. While single IA-12 samples exhibit roughly similar cytotoxicity, IA-12–oligonucleotide complexes show a selective effect toward M-HeLa cells (IC₅₀ 1.1 µM) compared to Chang liver cells (IC₅₀ 23.1 µM).     

Supramolecular Systems Based on Novel Mono‐ and Dicationic Pyrimidinic Amphiphiles and Oligonucleotides: A Self‐Organization and Complexation Study

Novel mono‐ and dicationic pyrimidinic surfactants are synthesized and their aggregation behavior is studied by methods of tensiometry and nuclear magnetic resonance (NMR) self‐diffusion. To estimate their potentiality as gene delivery agents, the complexation with oligonucleotides (ONus) is explored by dynamic light scattering (DLS) and zeta‐potential titration methods and ethidium bromide exclusion experiments. Bola‐type pyrimidinic amphiphile (BPM) demonstrates rather a weak affinity to ONus. Although it induces mixed associations with ONus, only slight charge compensation changes occur at a large excess of bola, with no recharging reached. Similarly, the ethydium bromide exclusion study reveals a slow increase in the binding capacity toward an ONu with an increment in BPM concentration. The monocationic pyrimidinic surfactant (MPM) and its gemini analogue (GPM‐1) are ranked as intermediates in both their aggregative activity and complexing properties toward ONus. They both form mixed associates with ONus well below the critical micelle concentrations (cmcs) of 2 and 15 mM respectively. However, GPM‐1 has a much lower isoelectric point at the molar ratio surfactant/ONu r～1 compared to r～3 for MPM. This probably indicates a larger electrostatic contribution to the ONu complexation in the case of GPM‐1. The most hydrophobic pyrimidinic surfactant (GPM‐2), bearing three alkyl tails, demonstrates enhanced aggregative activity and binding capacity toward ONus as compared to former pyrimidinic surfactants. Due to effective aggregative (low cmc of 0.04 mM ) plus binding properties (fraction of bound ONu β=0.76 at r=2.5), GPM‐2 may be ranked as a promising agent for wider biological applications.     

Supramolecular Catalytic Systems Based on a Cationic Amphiphile and Sodium Polystyrene Sulfonate for Decomposition of Organophosphorus Pollutants

Russian Journal of Organic Chemistry - A supramolecular catalytic system for hydrolytic decomposition of toxic phosphorus acid esters has been obtained on the basis of a cationic surfactant with a...     

Experimental Investigation of Thermo-Oscillatory Convection

The thermal convection in an air column oscillating with a high frequency in a plane channel whose boundaries are isothermal and have different temperatures is investigated. The experiments were performed for various channel orientations and for a wide range of nondimensional governing parameters, i.e. the gravitational Rayleigh number and the thermo-oscillatory parameter. As follows from the experimental results, for relatively large oscillation amplitudes the latter parameter characterizes the average action of high-frequency oscillations on a non-isothermal incompressible fluid. The regions in which either the thermo-oscillatory or gravitational mechanism of thermal convection predominates are determined. The threshold of excitation of thermo-oscillatory convection under weightlessness conditions is found.     

Reactivity of phosphorus esters in supramolecular systems based on surfactants containing an uracil residue and polyethylenimine

The reactivity of phosphorus esters with different hydrophobicities was studied in aqueous solutions of cationic surfactants containing an uracil residue, as well as in binary systems based on polyethylenimine. Pronounced substrate specificity was revealed in all supramolecular systems examined; in particular, acceleration of the hydrolysis of more hydrophobic substrate and inhibition of the reaction with less hydrophobic analog were observed. Aggregation in the examined systems was confirmed by tensiometric and conductometric measurements. The aggregation threshold considerably decreased in going from monocationic amphiphile to more hydrophobic dicationic analog due to the presence in the latter of two additional alkyl radicals.     

On the Asymptotic Integration of Quasilinear Differential Equations

Using the notion of convergence of solution spaces, we prove theorems about the asymptotic behavior of nearly linear systems. An example of an application of one of these theorems is given.     

On study of chemoselectivity of reaction of trialkylalanes with alkenes, catalyzed with Zr π-complexes

The influence of the organoaluminium compound nature, Zr π-ligand environment, solvent type and reagent ratio on the chemoselectivity of reactions of trialkylalanes (AlMe₃, AlEt₃) with alkenes, catalyzed with L₂ZrCl₂ [L = Cp, Cp′ (Cp′-η⁵-C₅H₄CH₃), Cp^∗ (Cp^∗-η⁵-C₅(CH₃)₅), Ind (indenyl), Flu (fluorenyl)] has been studied. It is shown that in the case of AlMe₃, the hydro- and carboalumination products, and alkene dimers are formed. The catalytic reaction of AlEt₃ with the olefins yields aluminacyclopentanes altogether with the hydro- and carboalumination products, and the dimers. A probable reaction mechanism has been proposed.