Receptor properties of calix[4]resorcinarenes toward tetramethylammonium and choline cations in micellar solutions of sodium dodecyl sulfate

Concentration range of solubilization of calix[4]resorcinarene (H 8L) in sodium dodecyl sulfate (SDS) micelles was found. The interaction of the deprotonated form of H8L (tetraanions [H4L] 4-) with tetramethylammonium (TMA) and choline cations in micellar solutions of SDS was studied by pH-metry and NMR spectroscopy. The concentration dependences of the change in the cloud point in a multicomponent system TMA (choline)-[H4L]4-SDS-tetrabutylammonium bromide were determined. A correlation of these dependences with host-guest binding processes was found. The sharp change in the cloud points of the corresponding micellar solutions in concentration regions of TMA (0-5.10-4 mol L -1) and choline (0-1.1.10-3 mol L-1) is caused by the formation of inclusion complexes TMA (choline)-[H4L] 4- at the interface of the aqueous and micellar pseudophases. © 2006 Springer Science+Business Media, Inc

Influence of the structure of nonionic surfactants and the length of alkyl substituents of calix[4]resorcinarenes on their solubility, acid-base, and complexation properties

Regularities of solubilization of calix[4]resorcinarenes (H8L) with the variable length of hydrophobic radicals (R = CH3, C 3H7, C5H11, C7H 15, C8H17, C9H19, C 11H23) by the micelles of nonionic surfactants Triton X-100 and Triton X-405 in aqueous solutions were studied using solubility measurements. It was found that the solubilization capacity of surfactant micelles with respect to H8L and [H4]4- depends on the extension (thickness) of their polar layers. It was shown by means of potentiometric titration that, in solutions of nonionic surfactants, the constants of the interaction between tetraanions [H4L]4- and tetrametylammonium ions depend on the structure and concentration of nonionic surfactants and the hydrophobicity of H8L molecules. A change in the affinity of the [H4L]4- anions for protons and tetramethylammonium cations in nonionic surfactant solutions was revealed in relation to the length of substituents R and reagent concentrations

Solubility, acid-base and complexation properties of calix[4]resorcinarene in aqueous solutions of nonionic surfactants

Solubility and acid-base properties of calix[4]resorcinarene (H8L) in aqueous solutions of nonionic surfactants Triton X-100, Triton X-405, and Brij-35, as well as isopropanol were studied by pH-potentiometry. The dependence of the amount of a nonionic surfactant necessary to dissolve H8L on the length of ethylene oxide chain was found. The dissociation constants of macrocycle for the first four steps are low sensitive to the medium nature (micellar or water-alcohol solutions). Complexation ability of the [H8-nL]n- anions with respect to tetramethyl- and tetraethylammonium, N-methylpyridinium, and [Co(En)2(C2O4)]+ cations was studied by pH-potentiometry. A noticeable increase in the selectivity of guest-host binding was found on going from aqueous or water-alcohol to micellar solutions

Solubilization and acidic and receptor properties of calix[4]resorcinarenes in aqueous solutions of oxyethylated dodecanol Brij-35

Solubilization of calix [4]resorcinarenes (Cn) with a varied length of hydrophobic substituents (R =Me, Pr, C5H11, C 7H15, C9H19, and C 11H23) in aqueous solutions of oxyethylated dodecanol Brij-35 was studied by the solubility method and 1D and 2D 1H NMR spectroscopy. The solubilization of Cn in micellar solutions of Brij-35 is caused by the formation of mixed Cn-Brij-35 aggregates and is weakened substantially with the elongation of R. It was shown by pH-metry and 1D 1H NMR spectroscopy that the receptor properties of the Cn anions toward the tetramethylammonium cations in the mixed aggregates differ substantially from those for the monomeric molecules in aqueous-organic and aqueous solutions. In particular, the binding of the tetramethylammonium cations does not result in screening of their N-Me fragments with the cyclophane cavity of the receptor. © 2005 Springer Science+Business Media, Inc

Extraction of lanthanum and gadolinium(III) at the cloud point using p-sulfonatocalyx[n]arenes as chelating agents

The extraction of gadolinium(III) and lanthanum(III) ions at the cloud point is studied in Triton X100 micellar solutions in a wide range of pH. In the absence of chelating agents, lanthanum(III) and gadolinium(III) ions are unselectively extracted at pH > 6. It is shown that the use of p-sulfonatothiacalyx[6(8)]arenes as chelating agents noticeably enhances the degree of extraction at pH 2-6. The composition and stability of lanthanum-p-sulfonatothiacalyx[n]arene complexes (n = 4, 6, 8) are estimated in a wide range of pH by pH-potentiometry. The degree of Gd3+ and La3+ ions extraction, which is performed at the cloud points employing calyxarene macrocycles of different sizes, is depended on the acidity of a medium. © 2009 Pleiades Publishing, Ltd

Fighting malaria without DDT : better management of the environment a key to disease control

French version available in IDRC Digital Library: Lutter contre le paludisme sans DDT : le contrôle de la maladie passe par une meilleure gestion de l'environnementSpanish version available in IDRC Digital Library: Combatiendo a la malaria sin DDT : mejor manejo ambiental, clave para el control de la enfermedadUnder the terms of the North American Free Trade Agreement, Mexico was committed to eliminating DDT use by 2002. The country’s malaria-control efforts, however, depended on this chemical. Researchers set about to develop alternate strategies by addressing factors that affect malaria’s spread: humans, mosquitoes, and the local environment in which the parasites persist. As a result of this integrated approach, Mexico was able to abandon DDT ahead of schedule

Sensing activity of cholinesterases through a luminescence response of the hexarhenium cluster complex [{Re<inf>6</inf>S<inf>8</inf>}(OH)<inf>6</inf>]^4-

© 2016 The Royal Society of Chemistry.The present work describes a new method to sense cholinesterase-catalyzed hydrolysis of acetylcholine (ACh) through a luminescence response of the hexarhenium cluster complex [{Re6S8}(OH)6]4-. A proton released from acetylcholinesterase (AChE)- or butyrylcholinesterase (BuChE)-catalyzed hydrolysis of ACh results in time-resolved sensitization of cluster-centered luminescence. The sensitization results from protonation of apical hydroxo-groups of the cluster complex. The protonation is affected by a counter ion effect. Thus, optimal conditions for adequate sensing of acetic acid produced by ACh hydrolysis are highlighted. Time-resolved luminescence and pH measurements under conditions of AChE-catalyzed hydrolysis of ACh show a good correlation between the cluster-centered luminescence and pH-induced inhibition of AChE. The inhibition is not significant within the first two minutes of ACh hydrolysis. Thus, the luminescence response measured within two minutes is dependent on both substrate and enzyme concentrations, which fits with AChE and BuChE kinetics. The usability of cluster-centered luminescence for monitoring the concentration-dependent inhibition of AChE with irreversible inhibitors is demonstrated, using a carbamylating agent, pyridostigmine bromide, as a model

The effect of temperature induced phase transitions in aqueous solutions of triblock copolymers and Triton X-100 on the EPR, magnetic relaxation and luminescent characteristics of Gd(III) and Eu(III) ions

The present report is inspired by the idea to develop novel spectroscopy based techniques to detect the phase transitions in solutions of triblock copolymers with the use of Gd(III) and Eu(III) ions as probes. The choice of (PEO)13(PPO)30(PEO)13 (L64), (PPO)14(PEO)24(PPO)14 (17R4), (PPO)8(PEO)22(PPO)8 (10R5) and Triton X-100 is conditioned by their phase transitions occurring in mild conditions. The cloud point extraction (CPE) data reveal the conditions (pH and chelating agent) where the binding of lanthanides with surfactant rich phase of triblock copolymers and Triton X-100 occurs. The effect of phase transitions in solutions of triblock copolymers on the temperature resolved line widths in EPR spectra of Gd(III) aqua ions and transverse relaxation rates of Gd(III) inner-sphere water protons depends on the architecture of triblock copolymers and pH conditions. The steady state luminescence of Eu(III) complexes with phosphine oxide in aqueous solutions of triblock copolymers and TX-100 is influenced by the temperature induced aggregation and phase separation in solutions of reverse triblock copolymers 17R4 and 10R5, while the effect of the aggregation is insignificant for L64. © 2012 Elsevier B.V

Екологічні аспекти в перспективі розвитку спеціальної економічної діяльності в Північному Приазов'ї

A comparative analysis of the quantitative model following the patterns of ecological development under the conditions of a free economic zone in the region of Northern Sea of Azov has been performed. The proportions and the annual growth rate of investment in the steel industry and alternative sectors of economy and their impact on the pollution level in the region have been defined. It has been shown that creation of the project of free economic zone in industrially developed regions must be followed by not only calculations of the investment policy economic efficiency, but also by the obligatory analysis of its influence on the level of ecological and social wellbeing of the population as well. Estimated data in proportions of investment policy in the region, ecologically safe and directed on welfare growth of the population have been defined on the basis of the analysis of the numerical model made up with the use of J. Forrester dynamic simulation technique and adapted for basic economic conditions. Problems of further researches are: refinement of some relationships to be able to calculate levels and rates dynamics of ecological and social blocks of the model to create the program of a steady development of Northern Sea of Azov regionВыполнен сравнительный расчет количественной модели по двум сценариям экологического развития в условиях свободной экономической зоны, в регионе Северного Приазовья. Определены пропорции и темпы роста ежегодных инвестиций, как в металлургическую промышленность края, так и в альтернативные отрасли экономики, и их влияние на уровень техногенной нагрузки в регионе. Показаны условия, не приводящие к росту общего объема превышений экологической емкости региона по отношению к исходному показателю в модели, и при этом способствующие росту материального уровня населения и его социальной защитыВиконаний порівняльний розрахунок кількісної моделі за двома сценаріями екологічного розвитку в умовах вільної економічної зони в регіоні Північного Приазов'я. Визначені пропорції і темпи зростання щорічних інвестицій, як в металургійну промисловість краю, так і в альтернативні галузі економіки, і їх вплив на рівень техногенного навантаження в регіоні. Показані умови, що не призводять до зростання загального об'єму перевищень екологічного потенціалу регіону, по відношенню до початкового показника в моделі, і при цьому сприяючі зростанню матеріального рівня населення і його соціального захист

Receptor properties of calix[4]resorcinarenes toward tetramethylammonium and choline cations in micellar solutions of sodium dodecyl sulfate

Concentration range of solubilization of calix[4]resorcinarene (H 8L) in sodium dodecyl sulfate (SDS) micelles was found. The interaction of the deprotonated form of H8L (tetraanions [H4L] 4-) with tetramethylammonium (TMA) and choline cations in micellar solutions of SDS was studied by pH-metry and NMR spectroscopy. The concentration dependences of the change in the cloud point in a multicomponent system TMA (choline)-[H4L]4-SDS-tetrabutylammonium bromide were determined. A correlation of these dependences with host-guest binding processes was found. The sharp change in the cloud points of the corresponding micellar solutions in concentration regions of TMA (0-5.10-4 mol L -1) and choline (0-1.1.10-3 mol L-1) is caused by the formation of inclusion complexes TMA (choline)-[H4L] 4- at the interface of the aqueous and micellar pseudophases. © 2006 Springer Science+Business Media, Inc