scholarly journals Zn2+ Interaction with Amyloid-Β: Affinity and Speciation

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2796 ◽  
Author(s):  
Arena ◽  
Rizzarelli
Keyword(s):  
Species Distribution ◽  
Multiple Equilibria ◽  
Amyloid Β ◽  
Data Interpretation ◽  
Amyloid Β Peptide ◽  
Experimental Conditions ◽  
Pros And Cons ◽  
The Stability ◽  
Ph Range

Conflicting values, obtained by different techniques and often under different experimental conditions have been reported on the affinity of Zn2+ for amyloid-β, that is recognized as the major interaction responsible for Alzheimer’s disease. Here, we compare the approaches employed so far, i.e., the evaluation of Kd and the determination of the stability constants to quantitatively express the affinity of Zn2+ for the amyloid-β peptide, evidencing the pros and cons of the two approaches. We also comment on the different techniques and conditions employed that may lead to divergent data. Through the analysis of the species distribution obtained for two selected examples, we show the implications that the speciation, based on stoichiometric constants rather than on Kd, may have on data interpretation. The paper also demonstrates that the problem is further complicated by the occurrence of multiple equilibria over a relatively narrow pH range.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

Factors affecting constancy of acetate concentration and correct determination of methanogenic activity in pH-stat experiments

2003 ◽  
Vol 48 (6) ◽  
pp. 111-118
Author(s):  
M. Mösche ◽  
U. Meyer
Keyword(s):  
Accurate Determination ◽  
Original Method ◽  
Experimental Conditions ◽  
Methanogenic Activity ◽  
Factors Affecting ◽  
Acetate Concentration ◽  
Correct Determination ◽  
Ph Stat ◽  
The Stability

The determination of methanogenic activity with a pH-stat titration bioassay is evaluated utilising a mathematical model of this system. For given kinetic parameters and experimental conditions the model calculates the development of titrant flow and acetate concentration during experiments. Simulations of experiments under various conditions are compared. They show that the original method inherently causes a strong drift of acetate concentration during the experiments and a misestimation of methanogenic activity. As a solution to these disadvantages the addition of sodium hydroxide to the titrant and a careful control of pH during flushing the reactor with gas prior to the experiment are recommended. In this way a better constancy of acetate concentration and a more accurate determination of methanogenic activity should be achievable. The accuracy of this method is limited by the stability of pH-electrode calibration parameters.

scholarly journals 2-Hydroxy-4-n-propoxy-5-bromoacetophenone oxime as an Analytical Reagent for Gravimetric Determination of V(V)

2009 ◽  
Vol 6 (2) ◽  
pp. 303-307 ◽  
Author(s):  
Ambily P. Nair ◽  
J. Christine
Keyword(s):  
Molar Absorptivity ◽  
Ratio Method ◽  
Gravimetric Determination ◽  
Pentavalent Vanadium ◽  
Analytical Reagent ◽  
Gibb’S Free Energy ◽  
The Stability ◽  
Ph Range ◽  
Job's Method

2-Hydroxy-4-n-propoxy-5-bromoacetophenone oxime (HnPBAO) was developed as a new analytical reagent for the gravimetric determination of pentavalent vanadium ion. In the pH range 4.0-6.0, the reagent gave a brown coloured precipitate with V(V). Job’s method and Mole ratio method revealed that the stoichiometry of the complex is 1:1 (metal: ligand). Beer’s law is obeyed up to 20.38 ppm of V(V). Molar absorptivity and Sandells sensitivity at 450 nm were found to be 10.22 × 102L/mol/cm and 0.049 µg/cm2respectively. The stability constant of V(V)-HnPBAO complex is found to be 1.195 × 106. Gibb’s free energy change for complex formation reaction was found to be –8.34 kcal/mol. The reagent can be used for the analysis of vanadium in ferro-vanadium alloys.

Evaluation of MALDI-TOF/TOF Mass Spectrometry Approach for Quantitative Determination of Aspartate Residue Isomerization in the Amyloid-β Peptide

2019 ◽  
Vol 30 (7) ◽  
pp. 1325-1329 ◽  
Author(s):  
Stanislav I. Pekov ◽  
Daniil G. Ivanov ◽  
Anna E. Bugrova ◽  
Maria I. Indeykina ◽  
Natalia V. Zakharova ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Quantitative Determination ◽  
Amyloid Β ◽  
Amyloid Β Peptide ◽  
Maldi Tof ◽  
Aspartate Residue

On the Hydrolysis of Tetravalent Metal Ions

2000 ◽  
Vol 663 ◽  
Author(s):  
C. Ekberg ◽  
P. Brown ◽  
J. Comarmond ◽  
Y. Albinsson
Keyword(s):  
Metal Ions ◽  
Stability Constants ◽  
Safety Assessment ◽  
Experimental Conditions ◽  
Polymeric Species ◽  
The Stability ◽  
Hydrolysis Of

ABSTRACTThe stability constants of the hydroxide complexes of zirconium(IV) and uranium(IV) have been measured at 15, 25 and 35°C [in 1.0 mol dm−3 (Na, H)ClO4] using potentiometry. For zirconium(IV), the results indicate the presence of Zr(OH)3+ and the polymeric species Zr3(OH)48+ and Zr4(OH)88+ whereas the results for uranium(IV) indicate the presence of U(OH)3+ and the polymeric species U4(OH)124+. The hydrolysis of both metal ions was studied at three temperatures allowing the determination of ΔH° and ΔS° of reaction for each species. The results were compared with previous results determined for thorium(IV) under the same experimental conditions to ascertain whether thorium should be used as an analogue for other tetravalent metal ions in safety assessment studies of nuclear repositories.

Capabilities of MS for Analytical Quantitative Determination of the Ratio of α- and βAsp7 Isoforms of the Amyloid-β Peptide in Binary Mixtures

2011 ◽  
Vol 83 (8) ◽  
pp. 3205-3210 ◽  
Author(s):  
Maria I. Indeykina ◽  
Igor A. Popov ◽  
Sergey A. Kozin ◽  
Alexey S. Kononikhin ◽  
Oleg N. Kharybin ◽  
...  
Keyword(s):  
Quantitative Determination ◽  
Binary Mixtures ◽  
Amyloid Β ◽  
Amyloid Β Peptide

Colorimetric determination of amyloid-β peptide using MOF-derived nanozyme based on porous ZnO-Co3O4 nanocages

2021 ◽  
Vol 188 (2) ◽  
Author(s):  
Xi Zhou ◽  
Shuangling Wang ◽  
Cong Zhang ◽  
Yulong Lin ◽  
Jie Lv ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Colorimetric Determination ◽  
Amyloid Β Peptide

scholarly journals Analysis and Optimization of Conditions for the Use of 2′,7′-Dichlorofluorescein Diacetate in Cultured Hepatocytes

Antioxidants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 674
Author(s):  
Megan J. Reiniers ◽  
Lianne R. de Haan ◽  
Laurens F. Reeskamp ◽  
Mans Broekgaarden ◽  
Rowan F. van Golen ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Data Interpretation ◽  
Medium Composition ◽  
Cultured Hepatocytes ◽  
Experimental Conditions ◽  
Membrane Transport Proteins ◽  
Dichlorofluorescein Diacetate ◽  
Cell Type Specific ◽  
The Stability

Numerous liver pathologies encompass oxidative stress as molecular basis of disease. The use of 2′,7′-dichlorodihydrofluorescein-diacetate (DCFH2-DA) as fluorogenic redox probe is problematic in liver cell lines because of membrane transport proteins that interfere with probe kinetics, among other reasons. The properties of DCFH2-DA were analyzed in hepatocytes (HepG2, HepaRG) to characterize methodological issues that could hamper data interpretation and falsely skew conclusions. Experiments were focused on probe stability in relevant media, cellular probe uptake/retention/excretion, and basal oxidant formation and metabolism. DCFH2-DA was used under optimized experimental conditions to intravitally visualize and quantify oxidative stress in real-time in HepG2 cells subjected to anoxia/reoxygenation. The most important findings were that: (1) the non-fluorescent DCFH2-DA and the fluorescent DCF are rapidly taken up by hepatocytes, (2) DCF is poorly retained in hepatocytes, and (3) DCFH2 oxidation kinetics are cell type-specific. Furthermore, (4) DCF fluorescence intensity was pH-dependent at pH < 7 and (5) the stability of DCFH2-DA in cell culture medium relied on medium composition. The use of DCFH2-DA to measure oxidative stress in cultured hepatocytes comes with methodological and technical challenges, which were characterized and solved. Optimized in vitro and intravital imaging protocols were formulated to help researchers conduct proper experiments and draw robust conclusions.

scholarly journals Reagent Activated Cotton Fiber for Rapid Determination of Aldehydes in Diverse Matrices

2021 ◽  
Vol 20 (3) ◽  
Author(s):  
S. Tantry Tantry ◽  
K. Tharpa ◽  
Ajay Kumar ◽  
Arun Kumar ◽  
B.H.S. Thimmappa
Keyword(s):  
Analytical Method ◽  
Cotton Fiber ◽  
Rapid Determination ◽  
Aqueous Sample ◽  
Exposure Limits ◽  
Experimental Conditions ◽  
Generation Cost ◽  
Permissible Exposure Limits ◽  
The Stability

A method to capture and analyze aldehydes in either solution or gas samples on cotton fiber, activated with O-benzyl hydroxylamine (OBA), is developed. The stability of the reagent activated cotton fiber (RACF) with and without capturing aldehydes was 17 days and 24 Hrs, respectively, qualifying the technique for field applications. Thus the aldehyde capturing can be done outside the lab using RACF in any closed environment and bring back to the lab for the quantitative analysis.. The analytical method is based on the gas chromatographic analysis of aldoxime formed between aldehydes and OBA on RACF. Optimized experimental conditions required 50 mg of RACF to capture aldehydes with a reaction time of 15 minutes. The technique detects aldehydes much below the permissible exposure limits of 25 ppm for acetaldehyde (CH3CHO) and 0.75 ppm for formaldehyde (HCHO). The method’s detection limits are 4 ppb of HCHO, 8 ppb of CH3CHO in the gas sample, and 1.5 ppb of HCHO, and 19 ppb of CH3CHO in the solution or aqueous sample. The analytical method was validated within the established quantitation ranges as per the required International Council for Harmonization Guidelines (CPMP/ICH/381/95). The RACF is a quick tool to measure aldehydes in a polymer sample, laboratory cupboards or refrigerators, and chemical products. The method described here complies with green analytical chemistry principles such as reduction in a solvent, chemical sample size and waste generation, cost-effectiveness, and usage of a biodegradable substrate.

scholarly journals Complex Equilibria and Distribution of Metal (II) Ions with Biologically Active Chelating Agents in Aqueous and Aqueous-organic Media

2021 ◽  
pp. 25-38
Author(s):  
K. T. Ishola ◽  
O. T. Olanipekun ◽  
O. T. Bolarinwa ◽  
R. D. Oladeji ◽  
A. Abubakar
Keyword(s):  
Metal Ions ◽  
Species Distribution ◽  
Ternary Complex ◽  
Aqueous System ◽  
Ternary Complexes ◽  
Teller Distortion ◽  
Complex Equilibria ◽  
Binary Complexes ◽  
The Stability ◽  
Ph Range

An understanding of the principles of complex equilibria and species distribution in different solutions is important in expounding and correlating the interaction of different ligands with different metal ions in complex formation. Therefore, acid-base equilibria involved in the formation of binary and ternary complexes of Co (II), Cu (II) and Pb (II) with methionine (Met) and uracil (Urc) have been determined by potentiometric titration technique. The stability constants of the complexes were evaluated at 35 ± 0.1°C and 0.02 M ionic strength (kept constant with NaNO3) in aqueous and organic-aqueous media. The species distribution in solutions as a function of pH was determined using the Hyss program. The stability of the ternary complexes relative to the corresponding binary complexes of the secondary ligand is measured in terms ΔlogK and % RS values. The ternary complexes are observed to be more stable than binary complexes in the media except for [CuMetUrc] ternary complex in organic-aqueous medium where the ternary complex is less stable than the binary complex of the uracil. The overall stability of the ternary complexes was higher in organic-aqueous system than aqueous system. The stability of the complexes was found to be correlated with the covalent index of the metal ions and Jahn Teller distortion. pH-studies of these systems revealed an increase in the concentrations of the ternary complexes with increase in pH. The formation of binary complexes was shown to be favoured in physiological pH range (3-7) while that of the ternary complexes is observed to be favoured in the pH range 5-10.

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