Search results for "aqueous solution"
showing 10 items of 1610 documents
Coordination properties of adenosine-5'-monophosphate and related ligands towards Me2Sn(IV)2+ in aqueous solution.
2002
Abstract The coordination of Me 2 Sn(IV) 2+ to adenosine-5′-monophosphate (AMP) and the related compounds d -ribose-5-phosphate (R5P), d -glucose-1-phosphate (G1P) and d -glucose-6-phosphate (G6P) in aqueous solution was investigated by means of potentiometric titration, and 1 H-, 31 P-NMR and Mossbauer spectroscopic methods in the pH range 2–11 ( I =0.1 M NaClO 4 , 298 K). The complex of AMP and Me 2 Sn(IV) 2+ precipitated at low pH was characterised by elemental analysis, FT-IR and Mossbauer spectroscopic methods. From a comparison of the p K values obtained in the presence and absence of metal ion and the stability constants for the different systems, the coordination of {N} is excluded,…
Dry adsorbed emulsion: 1. Characterization of an intricate physicochemical structure
2000
Abstract A recent solid pharmaceutical form called “Dry Adsorbed Emulsion” (DAE) was characterized in morphological and structural fields. A DAE is an intricate system initiated by a water‐in‐oil emulsion including the active drug (i.e., theophylline). Each emulsion phase is adsorbed on pulverulent adsorbents with a suitable polarity (silica) to obtain a free‐flowing powder with nonporous particles of size from 125 to 710 μm, with small specific surface area and a spherical shape. Different methods, such as scanning electron microscopy combined with chemical microanalysis, dying tests, and electron spin resonance studies, allow the formulator to follow the behavior of DAE aqueous and oily p…
Chemical Properties of Element 105 in Aqueous Solution: Halide Complex Formation and Anion Exchange into Triisoctyl Amine
2017
Studies of the halide complexation of element 105 in aqueous solution were performed on 34-s 262Ha produced in the 249Bk(18-O,5n) reaction. The 262Ha was detected by measuring the fission and alpha activities associated with its decay and the alpha decays of its daughter, 4.3-s 258Lr. Time-correlated pairs of parent and daughter alpha particles provided a unique identification of the presence of 262Ha. About 1600 anion exchange separations of 262Ha from HCl and mixed HC1/HF solutions were performed on a one-minute time scale. Reversed-phase micro-chromatographic columns incorporating triisooctyl amine (TIOA) on an inert support were used in the computer-controlled liquid chromatography appa…
Buildup of Ultrathin Multilayer Films by a Self-Assembly Process: II. Consecutive Adsorption of Anionic and Cationic Bipolar Amphiphiles and Polyelec…
1991
We have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions [1]. Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of…
Enhancing effect of alpha-hydroxyacids on "in vitro" permeation across the human skin of compounds with different lipophilicity.
2005
The percutaneous penetration-enhancing effects of glycolic acid, lactic acid and sodium lauryl sulphate through the human epidermis was investigated using 5-fluorouracil as a hydrophilic model permeant and three compounds belonging to the phenylalcohols: 2-phenyl-ethanol, 4-phenyl-butanol and 5-phenyl-pentanol. The lipophilicity values of the compounds ranged from log Poct -0.95 to 2.89. The effect of the enhancer concentration was also studied. Skin pretreatment with aqueous solutions of the three enhancers did not increase the permeability coefficient of the most lipophilic compound (log Poct = 2.89). For the other compounds assayed, the increase in the permeability coefficients depended …
Thermodynamic Behavior of Non-Ionic Tri-block Copolymers in Water at Three Temperatures
2006
Apparent molar volumes (V Φ) of aqueous solutions of some copolymers, based on ethylene oxide (EO) and propylene oxide (PO) units, were determined as functions of concentration at three temperatures. Viscosity measurements were also carried out on some of these systems. The effects studied include how the molecular architecture and the molecular weight affect the aggregation of the copolymer, keeping constant the EO/PO ratio. Modeling of the volumetric data yielded the partial molar volume of the copolymer in the standard (V°) and the aggregated (V M) states, as well as the equilibrium constant for micellization and the aggregation number. Analysis of the viscosity data supported the insigh…
Electrocatalytic properties of ferrooctacarboxyphthalocyanine(II). Electrocatalytic oxygen reduction on the mercury electrode in aqueous solutions
1996
Electrocatalytic reduction of oxygen in aqueous solutions in the presence of ferrooctacarboxyphthalocyanine was investigated. The decay of catalytic properties is attributed to the phthalocyanine aggregation. The mechanism for the four-electron electrocatalytic O2-reduction in neutral and basic media involving FePc(COOH)8 is proposed. It has been found that monomers of phthalocyanine, which are able to form μ-peroxo structures, are the catalytically active forms. The adsorption of various phthalocyanine forms on the mercury electrode plays a very important role in the overall catalytic reaction.
Spectral properties and aggregation of ferrooctacarboxyphthalocyanine(II) in aqueous solutions
1996
Spectral properties of ferrooctacarboxyphthalocyanine(II) in aqueous solutions are discussed. A special attention is paid to aggregation in the presence of electrolytes. The influence of many factors (concentration, pH etc.) on forms of its occurence is presented.
Impact of histidine spacing on modified polyhistidine tag – Metal ion interactions
2018
Abstract Histidine rich sequences are chosen both by nature and by molecular biologists due to their high affinity towards metal ions. In this work, we examine the affinity and binding modes of Cu 2+ , Ni 2+ and Zn 2+ towards two histidine tags, the common His 6 -tag (Ac-HHHHHH-NH 2 ) and its modified sequence, which also contains six histidines, but separated with two alanine residues (Ac-HAAHAAHAAHAAHAAHAA-NH 2 ). The spatial separation of histidines has an important impact on its coordination properties. Cu 2+ and Ni 2+ complexes with Ac-HHHHHH-NH 2 are more stable than those with Ac-HAAHAAHAAHAAHAAHAA-NH 2 ; the contrary is observed for Zn 2+ . In a narrow range of pH, Cu 2+ -Ac-HHHHHH-…
Tuning The Selectivity To Aldehyde Via Ph Regulation In The Photocatalytic Oxidation Of 4-Methoxybenzyl Alcohol And Vanillyl Alcohol By Tio2 Catalysts
2021
Abstract The influence of pH on the photocatalytic partial oxidation of 4-methoxybenzyl alcohol (MBA) and vanillyl alcohol (VA) to their corresponding aldehydes in aqueous suspension under UVA irradiation was investigated by using poorly crystalline home-prepared and crystalline commercial TiO2 (BDH, Merck and Degussa P25) photocatalysts. The results clearly show as tuning pH can strongly impart selectivity and activity to photocatalytic processes which are often quite unselective in aqueous suspensions. It was found that pH effect on reaction rate and product selectivity strongly depended on TiO2 crystallinity and substrate type. In the case of MBA oxidation, photoreactivity and selectivit…