Joanna Pranczk

Zinc(II) complexation by some biologically relevant pH buffers.

The isothermal titration calorimetry (ITC) technique supported by potentiometric titration data was used to study the interaction of zinc ions with pH buffer substances, namely 2‐(N‐morpholino)ethanesulfonic acid (Mes), piperazine‐N,N′‐bis(2‐ethanesulfonic acid) (Pipes), and dimethylarsenic acid (Caco). The displacement ITC titration method with nitrilotriacetic acid as a strong, competitive ligand was applied to determine conditional–independent thermodynamic parameters for the binding of Zn(II) to Mes, Pipes, and Caco. Furthermore, the relationship between the proposed coordination mode of the buffers and the binding enthalpy has been discussed. Copyright

Investigations of ternary complexes of Co(II) and Ni(II) with oxydiacetate anion and 1,10-phenanthroline or 2,2′-bipyridine in solutions

AbstractPotentiometric (PT) and conductometric (CT) titration methods have been used to determine the stoichiometry and formation constants in water for a series of ternary complexes of Co(II) and Ni(II) involving the oxydiacetate anion (ODA) and 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) ligands, namely [Co(ODA)(phen)(H2O)], [Co(ODA)(bpy)(H2O)], [Ni(ODA)(phen)(H2O)] and [Ni(ODA)(bpy)(H2O)]. The ternary complex formation process was found to take place in a stepwise manner in which the oxydiacetate ligand acts as a primary ligand and the phen or bipy ligands act as auxiliary ones. The stability of the ternary complexes formed is discussed in the relation to the corresponding binary ones. Furthermore, the kinetics of the substitution reactions of the aqua ligands in the coordination sphere of the Ni-ODA and Co-ODA complexes to phen or bipy were studied by the stopped-flow method. The kinetic measurements 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 (4–7 mM). The influence of experimental conditions and the kind of the auxiliary ligands (phen/bipy) on the substitution rate was discussed.

A novel biosensor for evaluation of apoptotic or necrotic effects of nitrogen dioxide during acute pancreatitis in rat.

The direct and accurate estimation of nitric dioxide levels is an extremely laborious and technically demanding procedure in the molecular diagnostics of inflammatory processes. The aim of this work is to demonstrate that a stop-flow technique utilizing a specific spectroscopic biosensor can be used for detection of nanomolar quantities of NO2 in biological milieu. The use of novel compound cis-[Cr(C2O4)(AaraNH2)(OH2)2]+ increases NO2 estimation accuracy by slowing down the rate of NO2 uptake. In this study, an animal model of pancreatitis, where nitrosative stress is induced by either 3g/kg bw or 1.5 g/kg bw dose of l-arginine, was used. Biochemical parameters and morphological characteristics of acute pancreatitis were monitored, specifically assessing pancreatic acinar cell death mode, NO2 generation and cellular glutathione level. The severity of the process correlated positively with NO2 levels in pancreatic acinar cell cytosol samples, and negatively with cellular glutathione levels.

Cis-[Cr(C2O4)(pm)(OH2)2]+ Coordination Ion as a Specific Sensing Ion for H2O2 Detection in HT22 Cells

The purpose of this study was to examine the application of the coordinated cis-[Cr(C2O4)(pm)(OH)2]+ cation where pm denotes pyridoxamine, as a specific sensing ion for the detection of hydrogen peroxide (H2O2). The proposed method for H2O2 detection includes two key steps. The first step is based on the nonenzymatic decarboxylation of pyruvate upon reaction with H2O2, while the second step is based on the interaction of cis-[Cr(C2O4)(pm)(OH2)2]+ with the CO2 released in the previous step. Using this method H2O2 generated during glutamate-induced oxidative stress was detected in HT22 hippocampal cells. The coordination ion cis-[Cr(C2O4)(pm)(OH2)2]+ and the spectrophotometric stopped-flow technique were applied to determine the CO2 concentration in cell lysates, supernatants and cell-free culture medium. Prior to CO2 assessment pyruvate was added to all samples studied. Pyruvate reacts with H2O2 with 1:1 stoichiometry, and consequently the amount of CO2 released in this reaction is equivalent to the amount of H2O2.

Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co2+ and Ni2+ ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N‐(2‐hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2‐(N‐morpholino)ethanesulfonic acid hydrate (2‐(N‐morpholino) ethanesulfonic acid), piperazine‐N,N′‐bis(2‐ethanesulfonic acid), and dimethylarsenic acid buffers (0.1 mol L−1, pH 6) at 298.15 K. The quantification of the metal‐buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH‐independent and buffer‐independent thermodynamic parameters (K, ΔG, ΔH, and ΔS) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co2+ and Ni2+ complexes and their thermodynamic stabilities are discussed.

The kinetics of substitution reaction of oxydiacetate and thiodiacetate copper(II) complexes with 1,10-phenanthroline and 2,2’-bipyridine

AbstractThe kinetics of substitution reactions of the CuODA and CuTDA binary complexes (ODA = oxydiacetate, TDA = thiodiacetate) with 1,10-phenanthroline (phen) and 2,2’-bipyridine (bipy) were studied in aqueous and DMSO solutions. These reactions were monitored spectrometrically using the stopped-flow method in the UV range. The studies were carried out at three temperatures - 298.15, 303.15 and 308.15 K. The concentrations of the binary complexes were kept within the range of 0.2–0.5 mmol L−1, whereas the concentration of phen or bipy was constant = 0.05 mmol L−1. The values of the reaction rate constants were calculated based on the A → B reaction model. A linear relationship of the rate of the substitution reaction versus the concentration of the binary complex as well as temperature was observed. The impact of the type of the primary (ODA and TDA) and auxiliary ligands (phen and bipy) as well as the effect of solvent on the rate of substitution reaction have been discussed. Graphical AbstractThe impact of the primary (ODA = oxydiacetate, TDA = thiodiacetate) and auxiliary ligands (phen and bipy) as well as the effect of solvents (DMSO and water) on the rate of substitution reaction of Cu(II) complexes have been discussed.

Kinetics of aquation of Ni(II) oxydiacetate complex induced by Fe(III) ions

The kinetics of the aquation reaction of [Ni(ODA)(H2O)3] (where ODA = oxydiacetate) promoted by [Fe(H2O)6]3+ ions were investigated. Spectrophotometry studies were carried out at temperatures within the range 293.15–313.15 K. The concentration of [Ni(ODA)(H2O)3] was 8.67 × 10–4 mol L–1 and the concentration of the [Fe(H2O)6]3+ ions was kept within the range 0.75 × 10–4–7.50 × 10–4 mol L–1. The observable reaction rate constants increased with the increase of [Fe3+] according to the rate law: kobs = k + k1K{[Fe(H2O)6]3+}. Based on the kinetic data, the activation parameters were determined for the spontaneous step of the reaction and for the step dependent on the concentration of Fe3+ ions. A mechanism for the aquation reaction has been proposed. In the first step (the reversible part of the aquation reaction) a dinuclear intermediate product is produced and in the next step the products of the reaction, ([Ni(H2O)6]2+ and [Fe(ODA)(H2O)3]+), are formed. Nevertheless, it has turned out that the spontaneous path of the aquation reaction is also possible concurrently (independent of the presence of Fe3+ ions). However, this process is too slow to be accurately measurable.

Kinetics of aquation of [Co(ODA)(H2O)3]induced by Fe(III)

Abstract The aquation reaction of the oxydiacetate cobalt(II) complex, namely [Co(ODA)(H2O)2]•H2O (ODA = oxydiacetate), induced by the Fe(III) ions as the promoter has been studied spectrophotometrically (UV-Vis). Kinetic measurements were carried out in the 283.15 - 303.15 K temperature range and at a constant ionic strength of 1.0 M (NaNO3). The observed rate constants were computed by a program based on global analysis. Furthermore, the reaction activation parameters were determined using the Arrhenius and Eyring equations. The changes in the enthalpy, entropy as well as activation energy barriers were calculated in the range of 0.00125 M – 0.125 M of the Fe(III) ion concentration. Based on kinetic data a mechanism for the aquation of the [Co(ODA)(H2O)3] complex has been proposed. Graphical Abstract