| 1. |
- Andersson, Ingegärd, et al.
(författare)
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Speciation in the aqueous H+/H2VO4–/H2O2/phosphate system
- 2005
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Ingår i: DALTON TRANSACTIONS. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 22, s. 3658-66
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Tidskriftsartikel (refereegranskat)abstract
- The speciation in the aqueous H+/H2VO4- /phosphate (dihydrogen phosphate, P) and H+/H2VO4/H2O2/P systems has been determined in the physiological medium of 0.150 M Na(Cl) at 25 degrees C. A combination of multinuclear NMR integral and chemical shift (Bruker AMX500) as well as potentiometric data (glass electrode) have been collected and treated simultaneously by the computer program LAKE. The pK(a)-values for phosphoric acid have been determined by potentiometric and P-31 NMR chemical shift data, and have been found to be 1.85 +/- 0.02, 6.69 +/- 0.02 and 11.58 +/- 0.07. The errors given are 3 sigma. Altogether nine vanadate phosphate species have been found in the ternary H+/H2VO4-/P- system in the PH region 1-11, with the following compositions: VP, VP2 and V14P. Equilibrium is very slow in acidic solutions, requiring more than 3 months for the formation of V14P species. On the other hand, less than 15 min are needed for equilibration at neutral and alkaline pH. In the H+/H2VO4-/H2O2/P- system, four new species have been found in addition to all binary and ternary complexes. They are of VXP and VX2P compositions, where X denotes the peroxo ligand. V-51 and P-31 NMR chemical shifts, compositions and formation constants are given, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. Biological and medical relevance of the species is also discussed and physiological conditions are modelled.
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| 2. |
- Bányai, István, et al.
(författare)
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On the Nature of VV Species in Hydrophilic Ionic Liquids: A Spectroscopic Approach
- 2008
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :34, s. 5373-81
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Tidskriftsartikel (refereegranskat)abstract
- Heteronuclear NMR experiments, in particular 51V, wereperformed with the aim to elucidate the nature of vanadates and peroxovanadates in hydrophilic ionic liquids (i.e., [bmim][BF4], [bmim][TfO] and [bdmim][BF4]). The data so far reported clearly indicate that ionic liquids have a strong influence on the solution chemistry of vanadate in water both for the formation of the aggregates (with and without H2O2) and for the rate of peroxide consumption catalyzed by vanadium. In BF4- containing ionic liquids, formation of vanadate-fluoride adducts is suggested. The obtained results are also discussed in the light of the reactivity data of peroxovanadates in ionic liquids.
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| 3. |
- González Baró, Ana, et al.
(författare)
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Speciation in the aqueous peroxovanadate-maltol and (peroxo)vanadate-uridine systems
- 2008
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 8, s. 1095-102
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Tidskriftsartikel (refereegranskat)abstract
- The speciation in the aqueous H+/H2VO4-/H2O2/maltol (Ma), H+/H2VO4-/uridine (Ur) and H+/H2VO4-/H2O2/Ur systems was determined in the physiological medium of 0.150 M Na(Cl) at 25 °C. A combination of quantitative 51V NMR (Bruker AMX500) and potentiometric data (glass electrode) was collected and treated simultaneously by the computer program LAKE. In the quaternary maltol system, the two species VXMa2- and VX2Ma2- (where X denotes the peroxo ligand) were found in the pH region 5-10, in addition to all binary and ternary complexes. Their formation was fast. In the ternary uridine (H+/H2VO4-/Ur) subsystem, altogether three vanadate-uridine (V-Ur) species were found in the pH region 4-10, with compositions VUr2-, V2Ur22- and V2Ur23-. Equilibrium was fast except in weakly acidic solutions when slowly decomposing decavanadates formed. In the quaternary H+/H2VO4-/H2O2/Ur system, five additional species were found at pH > 7. They were of VXUr and VX2Ur compositions. Their formation was fast. Formation constants, compositions and 51V NMR chemical shifts are given for all the species found in the systems, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. Biological and medical relevance of the species (in the treatment of diabetes) are also discussed, with pseudo-physiological conditions modelled.
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| 4. |
- Gorzsás, András, et al.
(författare)
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On the Fate of Vanadate in Human Blood
- 2006
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-0682. ; 18, s. 3559-65
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Tidskriftsartikel (refereegranskat)abstract
- The cover picture shows a symbolic representation of the fate of vanadate in human blood. Since the transition metal vanadium is named after Vanadis, the Nordic goddess of beauty, she is represented by the famous Venus de Milo sculpted in metal. Her cloth is decorated with the functional groups of the ligands that can form a complex (dress) with the metal while travelling in the blood vessels, the latter being symbolised by the caverns in the background. The water in the caves represents the aqueous solutions in which speciation studies have been carried out in the group of Professor Lage Pettersson. Further references to these studies are found as cave paintings on the walls: a distribution diagram and a set of 51V NMR spectra. The studies have been carried out in the framework of the COST D21/009 working group. The geographical locations of the research groups within this working group are shown by illuminated dots on the map of Europe in the background. The goal of the studies was to better understand the ability of vanadium to lower blood glucose levels (represented by the sugar cubes washed ashore on the left) and thus its potential as an orally applicable drug against diabetes. A Microreview, covering the results of the above mentioned speciation studies dealing with the fate of vanadate in human blood, is represented by A. Gorzsás, I. Andersson, and L. Pettersson on p. 3559 ff. The digital artwork for this cover was created by András Gorzsás.
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| 5. |
- Gorzsás, András, et al.
(författare)
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Speciation in Aqueous Vanadate – Ligand and Peroxovanadate – Ligand systems
- 2009
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Ingår i: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 103:4, s. 517-526
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Tidskriftsartikel (refereegranskat)abstract
- In the present focused review, the speciation studies of aqueous vanadate-ligand (L) and peroxovanadate-L systems are addressed. The paper focuses solely on the systems studied at our department in the context of potential insulin-enhancing effects, including the following ligands: imidazole, alanylhistidine, alanylserine, lactate, picolinate, citrate, phosphate, maltol, and uridine. We summarise the results of detailed and thorough potentiometric (glass electrode) and 51V NMR (Bruker AMX-500 MHz) spectroscopic studies, performed at 25 °C in 0.150 M Na(Cl), a medium representing human blood. The importance of experimental conditions is discussed and illustrated. A detailed overview of our methodology, based on combining potentiometric and 51V integral and chemical shift data by means of the computer program LAKE, is also given. We list the important steps of equilibrium analysis and the kinds of information available from different sets of NMR spectra. The ligand picolinate is chosen to exemplify our working method, but conclusions are drawn from all systems, reviewing trends and common features. An overview of all systems is given in two tables, including e.g. types and number of species formed. Previously unpublished modelling results at physiological conditions are also shown for all peroxovanadate-ligand systems.
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| 6. |
- Gorzsás, András, 1975-
(författare)
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Vanadate and Peroxovanadate Complexes of Biomedical Relevance : A speciation approach with focus on diabetes
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diabetes mellitus is one of the most threatening epidemics of modern times with rapidly increasing incidence. Vanadium and peroxovanadium compounds have been shown to exert insulin–like actions and, in contrast to insulin, are orally applicable. However, problems with side–effects and toxicity remain. The exact mechanism(s) by which these compounds act are not yet fully known. Thus, a better understanding of the aqueous chemistry of vanadates and peroxovanadates in the presence of various (bio)ligands is needed. The present thesis summarises six papers dealing mainly with aqueous speciation in different vanadate – and peroxovanadate – ligand systems of biological and medical relevance. Altogether, five ligands have been studied, including important blood constituents (lactate, citrate and phosphate), a potential drug candidate (picolinic acid), and a dipeptide (alanyl serine) to model the interaction of (peroxo)vanadate in the active site of enzymes. Since all five ligands have been studied both with vanadates and peroxovanadates, the number of systems described in the present work is eleven, including the vanadate – citrate – lactate mixed ligand system. The pH–independent formation constants have been determined for 33 ternary vanadate – ligand, 41 quaternary peroxovanadate – ligand and two vanadate – mixed ligand species in addition to the pKa values of all five ligands. These constants have been used to model physiological conditions, and the biomedical relevance of the different species is discussed. The studies have been performed at 25 ºC in the physiological medium of 0.150 M Na(Cl), i.e. the ionic strength of human blood. No buffers have been used, and wide pH–ranges have usually been covered. The applied experimental techniques comprise mostly 51V NMR and potentiometry, but 31P, 13C, 1H and 14N NMR as well as EPR and ESI–MS have also been used to gain additional information. Multimethod data have been treated by the least–squares program LAKE and modelling has been carried out by the software package WinSGW. Whenever possible, solution structures of the species have been proposed. In addition, simple biological tests have been carried out to determine the stability of the formed peroxovanadate complexes in the presence of human catalase. A brief comparison is given of the different vanadate – ligand and peroxovanadate – ligand systems with emphasis on observed trends and general features.
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| 7. |
- Hashimoto, Masato, et al.
(författare)
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A 31P-NMR study of the H+-MoO42--(HP)O32--HPO42--(C6H5P)O32--(CH3P)O32- system at low Motot/Ptot ratio - Formation of mixed-hetero X2M5-type polyanions
- 2009
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Ingår i: Dalton Transactions. - : The Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; :17, s. 3321-3327
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Tidskriftsartikel (refereegranskat)abstract
- Formation of X2M5-type heteropolyanions in the aqueous mixed-hetero H+-MoO42--(HP)O32--HPO42--(C6H5P)O32--(CH3P)O32- system has been studied by 31P-NMR at [Mo]tot/[Pall]tot = 1.5 at 298(1) K in 0.600 M Na(Cl) ionic medium. The -log[H+] range 1.4-6.2 has been covered. The pKa values of methylphosphonate were determined from 31P-NMR chemical shift data in the range of 0 < -log[H+] < 13.2 as H(CH3P)O3- 7.30 and H2(CH3P)O3 2.05. All four-component H+-MoO42--P1-P2 subsystems (P1 and P2 are two of the four phosphorus-containing components), except H+-MoO42--(HP)O32--HPO42-, which has been studied previously, were examined instead of the full six-component system in order to simplify the evaluation of the NMR spectra. The concentrations were adjusted to [Mo]tot = 60 mM and [P1]tot = [P2]tot = 20 mM in the measurements. All conceivable P2M5 and (P1)(P2)M5 heteropolyanions were identified. The following novel X2M5-type polyanions were found and their formation constants are given in logarithmic values with 3 in parentheses: (CH3P)2Mo5O214- 69.68(7), (HP)(C6H5P)Mo5O214- 67.09(4), (C6H5P)PMo5O225- 63.23(5), H(C6H5P)PMo5O224- 68.11(4), (HP)(CH3P)Mo5O214- 67.85(4), (CH3P)PMo5O225- 64.14(7), H(CH3P)PMo5O224- 68.89(4) and (C6H5P)(CH3P)Mo5O214- 69.18(4). The equilibrium conditions are illustrated in distribution diagrams. Phosphite proved to bind more weakly in X2M5-type polyoxometallates than phosphate or phosphonates, which are almost equally favoured in complexation.
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| 8. |
- Hashimoto, Masato, et al.
(författare)
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An equilibrium analysis of the aqueous H+- MoO4(2-)-(HP)O3(2-) and H+-MoO4(2-)-(HP)O3(2-)-HPO4(2-) systems
- 2007
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). ; , s. 124-32
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Tidskriftsartikel (refereegranskat)abstract
- The speciation in the phosphitomolybdate system, H+–MoO42––(HP)O32–, has been determined from combined potentiometric and 31P NMR measurements in 0.600 M Na(Cl) medium at 298(1) K. Potentiometric titration data were collected in the ranges 2.5 < –log[H+] < 6.2, 40.0 [Mo]tot 240.0 mM, 10.0 [P]tot 40.0 mM and 1 [Mo]tot/[P]tot 10. 31P NMR data were collected in the same ranges with the exception that –log[H+] was decreased to 0.8. The pKa values of phosphite were determined by means of potentiometric (1.5 < –log[H+] < 8.6) and 31P NMR chemical shift data (0.0 < –log[H+] < 12.0). The following log (3) values were deduced: H(HP)O3–, 6.09(2); H2(HP)O3, 7.23(4) (pKa = 1.14). In the phosphitomolybdate system, the following complexes were found along with their formation constants ((HP) denotes phosphite): Mo5(HP)24–, 65.31(4); Mo6(HP)25–, 71.94(5); Mo5(HP)4–, 51.25(8); Mo5(HP)3–, 54.9(3); Mo6(HP)2–, 68.99(9); Mo7(HP)5–, 71.25(3); Mo7(HP)4–, 74.2(2). Because hydrolysis and oxidation of phosphite to phosphate were observed by NMR, with a mixed-hetero species of low [Mo]tot/[P]tot ratio being detected, the four-component H+–MoO42––(HP)O32––HPO42– system was also studied in the same way over the range 0.8 < –log[H+] < 6.2 and [Mo]tot/[P]tot fixed at 1.5. The following mixed heteropolyanion species have been found (P denotes the phosphate group): Mo5(HP)P5–, 62.27(6); Mo5(HP)P4–, 66.76(4). The equilibrium speciation in the two systems are illustrated by distribution diagrams. In addition, the aqueous structures are proposed for all the species formed in the systems.
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