Electrochemical characterization of Cu(II) complexes of brain-related tau peptides

2021 ◽  
Vol 99 (7) ◽  
pp. 628-636
Author(s):  
Camilla Golec ◽  
Jose O. Esteves-Villanueva ◽  
Sanela Martic
Keyword(s):  
Metal Ions ◽  
Tau Protein ◽  
Metal Ion ◽  
Differential Pulse ◽  
Redox Couple ◽  
Peptide Sequence ◽  
Binding Studies ◽  
Biologically Relevant ◽  
Redox Active ◽  
Competition Binding

Metal ion dyshomeostasis plays an important role in diseases, including neurodegeneration. Tau protein is a known neurodegeneration biomarker, but its interactions with biologically relevant metal ions, such as Cu(II), are not fully understood. Herein, the Cu(II) complexes of four tau R peptides, based on the tau repeat domains, R1, R2, R3, and R4, were characterized by electrochemical methods, including cyclic voltammetry, square-wave voltammetry, and differential pulse voltammetry in solution under aerobic conditions. The current and potential associated with Cu(II)/(I) redox couple was modulated as a function of R peptide sequence and concentration. All R peptides coordinated Cu(II) resulting in a dramatic decrease in the current associated with free Cu(II), and the appearance of a new redox couple due to metallo–peptide complex. The metallo–peptide complexes were characterized by the irreversible redox couple at more positive potentials and slower electron-transfer rates compared with the free Cu(II). The competition binding studies between R peptides with Cu(II) indicated that the strongest binding affinity was observed for the R3 peptide, which contained 2 His and 1 Cys residues. The formation of complexes was also evaluated as a function of peptide concentration and in the presence of competing Zn(II) ions. Data indicate that all metallo–peptides remain redox active pointing to the potential importance of the interactions between tau protein with metal ions in a biological setting.

Bromine substituted aminonaphthoquinones: synthesis, characterization, DFT and metal ion binding studies

RSC Advances ◽  
2016 ◽  
Vol 6 (91) ◽  
pp. 88010-88029 ◽  
Author(s):  
Gunjan Agarwal ◽  
Dipali N. Lande ◽  
Debamitra Chakrovarty ◽  
Shridhar P. Gejji ◽  
Prajakta Gosavi-Mirkute ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Studies

Bromine substituted aminonaphthoquinones – chemosensors for metal ions.

scholarly journals Copper Complexing Capacity and Trace Metal Content in Common and Balsamic Vinegars: Impact of Organic Matter

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 861
Author(s):  
Sotirios Karavoltsos ◽  
Aikaterini Sakellari ◽  
Vassilia J. Sinanoglou ◽  
Panagiotis Zoumpoulakis ◽  
Marta Plavšić ◽  
...  
Keyword(s):  
Organic Matter ◽  
Metal Ions ◽  
Metal Ion ◽  
Metal Speciation ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Transition Metal Ions ◽  
Electrochemical Technique ◽  
Mass Unit

Complex formation is among the mechanisms affecting metal bioaccessibility. Hence, the quantification of organic metal complexation in food items is of interest. Organic ligands in solutions of environmental and/or food origin function as buffering agents against small changes in dissolved metal concentrations, being able to maintain free metal ion concentrations below the toxicity threshold. Organic matter in vinegars consists of bioactive compounds, such as polyphenols, Maillard reaction endproducts, etc., capable of complexing metal ions. Furthermore, transition metal ions are considered as micronutrients essential for living organisms exerting a crucial role in metabolic processes. In this study, differential pulse anodic stripping voltammetry (DPASV), a sensitive electrochemical technique considered to be a powerful tool for the study of metal speciation, was applied for the first time in vinegar samples. The concentrations of Cu complexing ligands (LT) in 43 vinegars retailed in Greece varied between 0.05 and 52 μM, with the highest median concentration determined in balsamic vinegars (14 μM), compared to that of common vinegars (0.86 μM). In 21% of the vinegar samples examined, LT values were exceeded by the corresponding total Cu concentrations, indicating the presence of free Cu ion and/or bound within labile inorganic/organic complexes. Red grape balsamic vinegars exhibited the highest density of Cu ligands per mass unit of organic matter compared to other foodstuffs such as herbal infusions, coffee brews, and beers. Among the 16 metals determined in vinegars, Pb is of particular importance from a toxicological point of view, whereas further investigation is required regarding potential Rb biomagnification.

scholarly journals Kinetic and equilibrium metal-ion-binding behaviour reflected in a metal-ion-dependent antigenic determinant in bovine prothrombin. Comparison with bovine prothrombin fragment 1

1981 ◽  
Vol 193 (2) ◽  
pp. 411-418 ◽  
Author(s):  
D A Madar ◽  
T J Hall ◽  
R G Hiskey ◽  
K A Koehler
Keyword(s):  
Metal Ions ◽  
Protein Conformation ◽  
Metal Ion ◽  
Ion Binding ◽  
Conformation Change ◽  
Metal Ion Binding ◽  
Binding Studies ◽  
Prothrombin Fragment ◽  
Absolute Requirement ◽  
Binding Behaviour

Rabbit anti-(bovine prothrombin fragment 1) antibodies were fractionated by using fragment-1 affinity chromatography in the absence of metal ions, and showed an absolute requirement for the presence of metal ions in their interactions with bovine fragment 1 or prothrombin. These antibodies were employed to evaluate both the rate constants for a protein conformation change and the equilibrium metal-ion binding to isolated bovine fragment 1 and intact prothrombin. The close similarity of the rates obtained for the conformation change in fragment 1 and those observed in prothrombin indicated that the same process is involved in both proteins and that the non-fragment-1 region of the prothrombin has essentially no effect on this process in the fragment-1 region. Equilibrium metal-ion-binding studies indicate that the details of the metal-ion-binding process in fragment 1 and prothrombin are essentially the same. We conclude that the metal-ion-binding behaviour of the fragment-1 domain of intact prothrombin is identical with that of isolated fragment 1.

scholarly journals Metal binding to the amyloid-β peptides in the presence of biomembranes: potential mechanisms of cell toxicity

2019 ◽  
Vol 24 (8) ◽  
pp. 1189-1196 ◽  
Author(s):  
Sebastian K. T. S. Wärmländer ◽  
Nicklas Österlund ◽  
Cecilia Wallin ◽  
Jinming Wu ◽  
Jinghui Luo ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Binding ◽  
Metal Ion ◽  
Membrane Surface ◽  
Membrane Damage ◽  
Amyloid Β ◽  
Metal Ion Binding ◽  
Aβ Oligomers ◽  
Redox Active ◽  
Active Metal

Abstract The amyloid-β (Aβ) peptides are key molecules in Alzheimer’s disease (AD) pathology. They interact with cellular membranes, and can bind metal ions outside the membrane. Certain oligomeric Aβ aggregates are known to induce membrane perturbations and the structure of these oligomers—and their membrane-perturbing effects—can be modulated by metal ion binding. If the bound metal ions are redox active, as e.g., Cu and Fe ions are, they will generate harmful reactive oxygen species (ROS) just outside the membrane surface. Thus, the membrane damage incurred by toxic Aβ oligomers is likely aggravated when redox-active metal ions are present. The combined interactions between Aβ oligomers, metal ions, and biomembranes may be responsible for at least some of the neuronal death in AD patients.

Study on the Development of a Cyclohexane Based Tripodal Molecular Device as "OFF-ON-OFF" pH Sensor and Fluorescent Iron Sensor

2020 ◽  
Vol 16 (5) ◽  
pp. 620-630 ◽  
Author(s):  
Vijay Dangi ◽  
Minati Baral ◽  
B.K. Kanungo
Keyword(s):  
Metal Ions ◽  
Ph Sensor ◽  
Maximum Deviation ◽  
Theoretical Studies ◽  
Dft Studies ◽  
Binding Studies ◽  
Deprotonated Form ◽  
Weak Band ◽  
Biologically Relevant ◽  
Td Dft

Background: Iron is an essential transition metal which is indispensable for life processes like oxygen transport and metabolism, electron transfer etc. However, misregulated iron is responsible for disease like anemia, hemochromatosis, Alzheimer’s and Parkinson’s disease. In order to encounter these diseases, a better understanding is needed of its role in misregulation. Fluorescent iron sensors could help provide this information. The new chemosensor developed by linking a cyclohexane unit with three 8-hydroxyquinoline provides selective detection of iron in numerous biological and environmental samples. Methods: The Uv-visible and fluorescence spectroscopy in combination with pH measurements will mainly be used for the study. Theoretical studies at DFT level will be used to validate the method and explain the theory behind the experiments. Results: The study of electronic spectra of the chelator, HQCC, reveals the appearance of a band at 262 nm along with a weak band at 335 nm due to π- π* and n- π* transitions respectively. Upon excitation with 335 nm, the ligand fluoresces at 388 nm wavelength. The intensity of the emission was affected in presence of metal ions, with maximum deviation for Fe(III). Selectivity studies showed that Fe(III) is more selective as compared to the biologically relevant metal ions viz., Al(III), Fe(III), Cr(III), Co(II), Fe(II), Ni(II), Zn(II), Cu(II), Mn(II) and Pb(II). pH dependent studies implied that the fluorescence intensity was highest at pH ~8.0, whereas maximum quenching for iron-HQCC system was observed at pH 7.4. The binding studies from the B-H plot confirms the formation of 1:1 complex with association constant of 5.95 × 106. The results obtained from experiments were in agreement with that obtained from the DFT and TD-DFT studies. Conclusion: A novel tripodal chelator based on 8-hydroxyquinoline and symmetric cyclohexane scaffold was successfully developed. In addition to the excellence of the ligand to be employed as a promising sensitive fluorescent probe for easy detection of Fe3+ions at the physiological pH with very low concentration (7.5 x 10-5 molL-1), the new ligand can be used as an OFF-ON-OFF pH sensor. Fe(III) encapsulation along with 1:1 ML-complexation formation have been established. Theoretical studies confirm a d-PET mechanism for the fluorescence quenching. DFT studies revealed that the neutral form of the ligand is less reactive than its protonated or the deprotonated form.

Use of agro-waste (Musa paradisiaca peels) as a sustainable biosorbent for toxic metal ions removal from contaminated water

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Contact Time ◽  
Metal Ion ◽  
Equilibrium Concentration ◽  
Ion Concentration ◽  
Contaminated Water ◽  
Musa Paradisiaca ◽  
Percentage Removal ◽  
Adsorbent Dose

A study of removal of heavy metal ions from heavy metal contaminated water using agro-waste was carried out with Musa paradisiaca peels as test adsorbent. The study was carried by adding known quantities of lead (II) ions and cadmium (II) ions each and respectively into specific volume of water and adding specific dose of the test adsorbent into the heavy metal ion solution, and the mixture was agitated for a specific period of time and then the concentration of the metal ion remaining in the solution was determined with Perkin Elmer Atomic absorption spectrophotometer model 2380. The effect of contact time, initial adsorbate concentration, adsorbent dose, pH and temperature were considered. From the effect of contact time results equilibrium concentration was established at 60minutes. The percentage removal of these metal ions studied, were all above 90%. Adsorption and percentage removal of Pb2+ and Cd2+ from their aqueous solutions were affected by change in initial metal ion concentration, adsorbent dose pH and temperature. Adsorption isotherm studies confirmed the adsorption of the metal ions on the test adsorbent with good mathematical fits into Langmuir and Freundlich adsorption isotherms. Regression correlation (R2) values of the isotherm plots are all positive (>0.9), which suggests too, that the adsorption fitted into the isotherms considered.

The Binding and Viscometric Studies of Ni+2, Co+2 and Mn+2 Ions with Protein by Spectrometric and pH Metric Techniques

2019 ◽  
Vol 9 (2) ◽  
pp. 151-162
Author(s):  
Shveta Acharya ◽  
Arun Kumar Sharma
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Protein Molecule ◽  
Vital Role ◽  
Sufficient Evidence ◽  
Structural Requirement ◽  
Nickel Ions ◽  
Cobalt Ions ◽  
Lower Temperature ◽  
Specific Oxidation

Background: The metal ions play a vital role in a large number of widely differing biological processes. Some of these processes are quite specific in their metal ion requirements. In that only certain metal ions, in specific oxidation states, can full fill the necessary catalytic or structural requirement, while other processes are much less specific. Objective: In this paper we report the binding of Mn (II), Ni (II) and Co (II) with albumin are reported employing spectrophotometric and pH metric method. In order to distinguish between ionic and colloidal linking, the binding of metal by using pH metric and viscometric methods and the result are discussed in terms of electrovalent and coordinate bonding. Methods: The binding of Ni+2, Co+2 and Mn+2 ions have been studied with egg protein at different pH values and temperatures by the spectrometric technique. Results: The binding data were found to be pH and temperature dependent. The intrinsic association constants (k) and the number of binding sites (n) were calculated from Scatchard plots and found to be at the maximum at lower pH and at lower temperatures. Therefore, a lower temperature and lower pH offered more sites in the protein molecule for interaction with these metal ions. Statistical effects seem to be more significant at lower Ni+2, Co+2 and Mn+2 ions concentrations, while at higher concentrations electrostatic effects and heterogeneity of sites are more significant. Conclusion: The pH metric as well as viscometric data provided sufficient evidence about the linking of cobalt, nickel and manganese ions with the nitrogen groups of albumin. From the nature and height of curves in the three cases it may be concluded that nickel ions bound strongly while the cobalt ions bound weakly.

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