scholarly journals A study of 12-tungstosilicic and 12-molybdophosphoric acids in solution

2008 ◽  
Vol 73 (2) ◽  
pp. 197-209 ◽  
Author(s):  
Danica Bajuk-Bogdanovic ◽  
Ivanka Holclajtner-Antunovic ◽  
Marija Todorovic ◽  
Ubavka Mioc ◽  
Joanna Zakrzewska
Keyword(s):  
Nmr Spectroscopy ◽  
Aqueous Solutions ◽  
Special Importance ◽  
Molybdophosphoric Acid ◽  
Physiological Conditions ◽  
Tungstosilicic Acid ◽  
Ir And Nmr Spectroscopy ◽  
Wide Range ◽  
Catalytic Applications ◽  
Anion Type

The behaviour of two heteropolyacids (HPAs) with quite different stability in aqueous solutions was systematically investigated by UV, IR and NMR spectroscopy and potentiometric titration. It was shown that the Keggin structure of 12-tungstosilicic acid (H4SiW12O40, WSiA) anion was sustained over a wide range of pH from 1.0 to 7.0, while the same anion type of 12-molybdophosphoric acid (H3PMo12O40, MoPA) was present only at pH 1.0. This means that under physiological conditions WSiA is dominantly present in the form of a Kegginanion, whereas the structure of MoPA is completely decomposed to molybdate and phosphate. The obtained results are of special importance for bio-medical and catalytic applications of these compounds and for a better understanding of the mechanism of their action.

Sectroscopic study of stability and molecular species of 12-tungstophosphoric acid in aqueous solution

2008 ◽  
Vol 86 (10) ◽  
pp. 996-1004 ◽  
Author(s):  
Ivanka Holclajtner-Antunović ◽  
Danica Bajuk-Bogdanović ◽  
Marija Todorović ◽  
Ubavka B Mioč ◽  
Joanna Zakrzewska ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Species ◽  
Ph Value ◽  
Equilibrium Composition ◽  
Keggin Structure ◽  
Special Importance ◽  
Keggin Anion ◽  
Ph Values ◽  
Ir And Nmr Spectroscopy ◽  
Ph Range

The various molecular species of 12-tungstophosporic acid (WPA) in aqueous solutions of different pH values (from 1 to 11.5) were investigated by UV, IR, and NMR spectroscopy. The dependence of the attained equilibrium composition in solution on time, concentration of WPA, and type of buffer used was studied. Obtained results indicate that the buffer type and pH value greatly determine the equilibrium composition in the solution. The Keggin structure of the WPA is sustained only up to pH 1.5. With further increase in pH, the decomposition of Keggin anion does not lead directly to the monovacant lacunary anion. Between 1.5 and 2.0, the structures with 2 phosphorus atoms from the Dawson series are dominant as intermediate species. In the pH range 3.5–7.5, WPA is present in the form of the monovacant lacunary Keggin anion. These results are of special importance for the biomedical and catalytic applications of heteropoly compounds (HPCs) and for an improved understanding of the mechanism of their functioning.Key words: heteropolyacids of the Keggin structure, hydrostability, UV, IR and NMR spectroscopy.

scholarly journals Monoalkylcarbonate Formation in the System Monoethanolamine-water-carbon Dioxide

2021 ◽  
Author(s):  
Richard Behrens ◽  
Elmar Kessler ◽  
Kerstin Münnemann ◽  
Hans Hasse ◽  
Erik von Harbou
Keyword(s):  
Carbon Dioxide ◽  
Nmr Spectroscopy ◽  
Aqueous Solutions ◽  
Comprehensive Data ◽  
Wide Range ◽  
Carbon Dioxide Co2

In a recent study, we have shown by NMR spectrocopy that monoalkylcarbonates are formed in substantial amounts in aqueous solutions of the tertiary alkanolamine methyldiethanolamine (MDEA) upon loading with carbon dioxide (CO2). These species had been overlooked by most authors previously. In the present work, this study was extended to the primary alkanolamine monoethanolamine (MEA). Also here monoalkylcarbonates were found, but only at CO2 loadings above 0.5 mol CO2 per mol MEA. Both the amine and its carbamate form monoalkylcarbonates. The concentration of the monoalkylcarbonates was determined with C-13 NMR spectroscopy in a wide range of CO2 loadings, MEA concentrations, and temperatures. Based on this comprehensive data the chemical equilibirium constants of the formation of the monoalkylcarbonates were determined. (C) 2019 Elsevier B.V. All rights reserved.

Synthesis and Caracterization of some New 1H-3-aryl-7-etoxycarbonyl-6-methyl-pyrazolo[5,1-c][1,2,4]triazoles

2008 ◽  
Vol 59 (1) ◽  
pp. 41-44
Author(s):  
Maria-Daniela Sofei ◽  
Maria Ilici ◽  
Valentin Badea ◽  
Carol Csunderlik ◽  
Vasile-Nicolae Bercean
Keyword(s):  
Mass Spectrometry ◽  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Sodium Acetate ◽  
Glacial Acetic Acid ◽  
Ir And Nmr Spectroscopy

The synthesis of 1H-3-aryl-7-ethoxycarbonyl-6-methyl-pyrazolo[5,1-c][1,2,4]triazoles (2) was carried out by cyclization of 1H-5-arylidenehydrazino-4-ethoxycarbonyl-3-methyl-pyrazoles (1) in the presence of bromine using glacial acetic acid as solvent and sodium acetate as base. The new nine obtained compounds were characterized by IR and NMR spectroscopy and mass spectrometry.

Molecular Dynamics Simulation of the Aggregation Patterns in Aqueous Solutions of Bile Salts at Physiological Conditions

2015 ◽  
Vol 119 (51) ◽  
pp. 15631-15643 ◽  
Author(s):  
Fatmegyul Mustan ◽  
Anela Ivanova ◽  
Galia Madjarova ◽  
Slavka Tcholakova ◽  
Nikolai Denkov
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Aqueous Solutions ◽  
Bile Salts ◽  
Dynamics Simulation ◽  
Physiological Conditions

Synthesis, Characterization and Complexation Studies with K + and Ca2+ Cations of trans-1.2-Cyclohexanedioxydiacetamides

1988 ◽  
Vol 43 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Whei Oh Lin ◽  
Maria C. B. V. de Souza ◽  
Helmut G. Alt
Keyword(s):  
Nmr Spectroscopy ◽  
Mass Spectroscopy ◽  
H Nmr ◽  
Coordination Sites ◽  
Complexation Studies ◽  
Ir And Nmr Spectroscopy ◽  
Elemental Analyses ◽  
C Nmr

The synthesis of trans-1.2-cyclohexanedioxydiacetamides starting with trans-1.2-cyclohexane-diol is described. Eleven of these compounds are characterized by IR, 1H NMR, 13C NMR and mass spectroscopy as well as elemental analyses. Most of these compounds are suitable ionophors for the cations K+ and Ca2+. The coordination sites of these ligands in the 1:2 complexes were determined by IR and NMR spectroscopy

Modeling of the Extraction of Lanthanide Nitrates from Aqueous Solutions Over a Wide Range of Activities by CMPO

2004 ◽  
Vol 22 (5) ◽  
pp. 791-811 ◽  
Author(s):  
S. Belair ◽  
C. Lamouroux ◽  
M. Tabarant ◽  
A. Labet ◽  
C. Mariet ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Wide Range ◽  
Lanthanide Nitrates

scholarly journals Characterization of nucleosome sediments for protein interaction studies by solid-state NMR spectroscopy

2021 ◽  
Author(s):  
Ulric B. le Paige ◽  
ShengQi Xiang ◽  
Marco M. R. M. Hendrix ◽  
Yi Zhang ◽  
Markus Weingarth ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Dense Phase ◽  
Binding Studies ◽  
Nmr Studies ◽  
Solid State Nmr Spectroscopy ◽  
Wide Range

Abstract. Regulation of DNA-templated processes such as gene transcription and DNA repair depend on the interaction of a wide range of proteins to the nucleosome, the fundamental building block of chromatin. Both solution and solid-state NMR spectroscopy have become an attractive approach to study the dynamics and interactions of nucleosomes, despite their high molecular weight of ~200 kDa. For solid-state NMR (ssNMR) studies, dilute solutions of nucleosomes are converted to a dense phase by sedimentation or precipitation. Since nucleosomes are known to self-associate, these dense phases may induce extensive interactions between nucleosomes, which could interfere with protein binding studies. Here, we characterized the packing of nucleosomes in the dense phase created by sedimentation using NMR and small-angle x-ray scattering (SAXS) experiments. We found that nucleosome sediments are gels with variable degrees of solidity, have nucleosome concentration close to that found in crystals, and are stable for weeks under high-speed magic angle spinning (MAS). Furthermore, SAXS data recorded on recovered sediments indicate that there is no pronounced long-range ordering of nucleosomes in the sediment. Finally, we show that the sedimentation approach can also be used to study low affinity protein interactions with the nucleosome. Together, our results give new insights into the sample characteristics of nucleosome sediments for ssNMR studies and illustrate the broad applicability of sedimentation-based NMR studies.

scholarly journals Stability Evaluation and Degradation Studies of DAC® Hyaluronic-Polylactide Based Hydrogel by DOSY NMR Spectroscopy

Biomolecules ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1478
Author(s):  
Tatiana Guzzo ◽  
Fabio Barile ◽  
Cecilia Marras ◽  
Davide Bellini ◽  
Walter Mandaliti ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Nmr Spectroscopy ◽  
Bone Growth ◽  
Orthopedic Implants ◽  
Structured Surfaces ◽  
Physiological Conditions ◽  
Hydrophilic Character ◽  
Dosy Nmr ◽  
The Stability

The stability and the degradation of polymers in physiological conditions are very important issues in biomedical applications. The copolymer of hyaluronic acid and poly-D,L-lactic acid (made available in a product called DAC®) produces a hydrogel which retains the hydrophobic character of the poly-D,L-lactide sidechains and the hydrophilic character of a hyaluronic acid backbone. This hydrogel is a suitable device for the coating of orthopedic implants with structured surfaces. In fact, this gel creates a temporary barrier to bacterial adhesion by inhibiting colonization, thus preventing the formation of the biofilm and the onset of an infection. Reabsorbed in about 72 h after the implant, this hydrogel does not hinder bone growth processes. In the need to assess stability and degradation of both the hyaluronan backbone and of the polylactic chains along time and temperature, we identified NMR spectroscopy as a privileged technique for the characterization of the released species, and we applied diffusion-ordered NMR spectroscopy (DOSY-NMR) for the investigation of molecular weight dispersion. Our diffusion studies of DAC® in physiological conditions provided a full understanding of the product degradation by overcoming the limitations observed in applying classical chromatography approaches by gel permeation UV.

Sign in / Sign up

Export Citation Format

Share Document