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Miquel Esteban - One of the best experts on this subject based on the ideXlab platform.
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comparison of Differential Pulse and alternating current Polarography in the soft modelling study of the complexation of cd ii by the fragment cys gly and by the phytochelatin γ glu cys 2gly
Analytical and Bioanalytical Chemistry, 2008Co-Authors: Anna Maria Garrigosa, Cristina Arino, Jose Manuel Diazcruz, Miquel EstebanAbstract:A comparison of a Differential Pulse polarographic with a phase sensitive alternating current polarographic study of the Cd-Cys-Gly and Cd-PC2 systems [PC2 being a phytochelatin of general structure (γ-Glu-Cys) n -Gly, with n = 2] has been performed. The chemometric multivariate curve resolution method with alternating least squares was applied in the experimental data analysis. The results obtained by both polarographic techniques have made it possible to find out the formation sequences of the complexes and their final stoichiometries. The alternating current polarograms compared with the Differential Pulse ones show some differences (a new signal and an important shift of peak potentials), which anyway are consistent with some of the conclusions obtained by Differential Pulse Polarography. This fact implies that although the alternating current Polarography results need some corrections before data treatment, they provide extra information that complements the conclusions achieved by Differential Pulse Polarography.
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combined use of Differential Pulse Polarography and multivariate curve resolution as applied to the study of metal mixed complexes of the metallothionein related hexapeptide
Electroanalysis, 2002Co-Authors: Silvia M Diazcruz, Jesús Mendieta, Miquel EstebanAbstract:The complexation of the hexapeptide Lys-Cys-Thr-Cys-Cys-Ala (FT), peptidic fragment {56–61} of mouse liver metallothionein MT I, in the presence of both Cd(II) and Zn(II) is investigated as a model to understand the metal-binding properties of natural MT's, in which Cd and Zn are simultaneously present. The influence of Cd(II) or Zn(II) on the complexing behavior of FT with Zn(II) or Cd(II), respectively, is studied using the combined techniques of Differential Pulse Polarography and multivariate curve resolution with alternating least square optimization (MCR-ALS). MCR-ALS allows both the unitary voltammograms for each electrochemical process and the concentration profiles of the different species present in the system to be obtained during the experiment, thereby providing a rough picture of the processes involved. Our results allow us to propose the formation of Cd2ZnFT2 and CdZn2FT2 complexes.
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Complexation of cadmium by the C-terminal hexapeptide Lys-Cys-Thr-Cys-Cys-Ala from mouse metallothionein: study by Differential Pulse Polarography and circular dichroism spectroscopy with multivariate curve resolution analysis
Analytica Chimica Acta, 1999Co-Authors: Jesús Mendieta, M.s Dı́az-cruz, A Monjonell, R. Tauler, Miquel EstebanAbstract:Abstract The cadmium-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys-Cys-Thr-Cys-Cys-Ala, were studied by circular dichroism spectroscopy (CD), Differential Pulse Polarography (DPP) and 113 Cd-nuclear magnetic resonance (NMR). The structure of the multiple cadmium binding sites could not be determined by 113 Cd-NMR because of the insolubility of the Cd–peptide samples at the high concentrations required for NMR. Therefore, alternative approaches were used: CD and DPP. The data were analyzed using a multivariate curve resolution (MCR) approach, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. The CD study confirmed that the binding of Cd 2+ induces important conformational changes in the structure of the peptidic complex, including the formation of a binuclear cluster. The DPP results obtained at various Cd 2+ -to-peptide concentration ratios and pH values, under conditions where electrode adsorption is low, if not negligible, indicated the formation of different Cd 2+ –peptide complexes, and a scheme for the electrochemical reduction of the complexed Cd 2+ ions is proposed. These results show that the application of MCR to complex data, such as those from DPP, allows to reach valuable information which is not possible to be obtained by univariate approaches.
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zinc binding properties of the c terminal hexapeptide lys cys thr cys cys ala from mouse metallothionein analysis by Differential Pulse Polarography and multivariate curve resolution
Analytica Chimica Acta, 1999Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The zinc-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys–Cys–Thr–Cys–Cys–Ala, were studied by Differential Pulse Polarography (DPP) with a recently proposed multivariate curve resolution (MCR) method, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. From DPP results obtained at different Zn 2+ -to-peptide concentration ratios and at different pH values, the formation of different Zn 2+ –peptide complexes is deduced, and a scheme for the electrochemical reduction of the complexed Zn 2+ ions is proposed. Two complexes have been detected: the first one is formed at low Zn-to-FT concentration ratios and shows a 1:2 Zn:FT stoichiometry; at higher ratios a second Zn 2+ is incorporated yielding a Zn 2 FT 2 complex which probably contains a binuclear cluster.
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study of the zinc binding properties of glutathione by Differential Pulse Polarography and multivariate curve resolution
Journal of Inorganic Biochemistry, 1998Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The complexation between Zn 2+ and glutathione (GSH), in borate buffer, is studied by Differential Pulse Polarography (DPP). Data obtained at pH 8.5 from a titration of Zn 2+ by GSH, i.e. at different GSH-to-Zn 2+ concentration ratios have been analyzed by a recently proposed multivariate curve resolution method. DPP signals obtained within a wide pH range, but at fixed 1.25:1 GSH-to-Zn 2+ concentration ratios, have been resolved individually at each pH value. Results from both sets of experiments can be explained with a complexation model involving the formation of a predominant complex, with a stoichiometry of 2:2 GSH : Zn 2+ .This result is in contrast with those for the Cd 2+ –GSH systems, where two complexes, 2:1 and 2:2 GSH : Cd 2+ , were detected. A scheme for the global electrode process is given.
Jesús Mendieta - One of the best experts on this subject based on the ideXlab platform.
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combined use of Differential Pulse Polarography and multivariate curve resolution as applied to the study of metal mixed complexes of the metallothionein related hexapeptide
Electroanalysis, 2002Co-Authors: Silvia M Diazcruz, Jesús Mendieta, Miquel EstebanAbstract:The complexation of the hexapeptide Lys-Cys-Thr-Cys-Cys-Ala (FT), peptidic fragment {56–61} of mouse liver metallothionein MT I, in the presence of both Cd(II) and Zn(II) is investigated as a model to understand the metal-binding properties of natural MT's, in which Cd and Zn are simultaneously present. The influence of Cd(II) or Zn(II) on the complexing behavior of FT with Zn(II) or Cd(II), respectively, is studied using the combined techniques of Differential Pulse Polarography and multivariate curve resolution with alternating least square optimization (MCR-ALS). MCR-ALS allows both the unitary voltammograms for each electrochemical process and the concentration profiles of the different species present in the system to be obtained during the experiment, thereby providing a rough picture of the processes involved. Our results allow us to propose the formation of Cd2ZnFT2 and CdZn2FT2 complexes.
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Complexation of cadmium by the C-terminal hexapeptide Lys-Cys-Thr-Cys-Cys-Ala from mouse metallothionein: study by Differential Pulse Polarography and circular dichroism spectroscopy with multivariate curve resolution analysis
Analytica Chimica Acta, 1999Co-Authors: Jesús Mendieta, M.s Dı́az-cruz, A Monjonell, R. Tauler, Miquel EstebanAbstract:Abstract The cadmium-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys-Cys-Thr-Cys-Cys-Ala, were studied by circular dichroism spectroscopy (CD), Differential Pulse Polarography (DPP) and 113 Cd-nuclear magnetic resonance (NMR). The structure of the multiple cadmium binding sites could not be determined by 113 Cd-NMR because of the insolubility of the Cd–peptide samples at the high concentrations required for NMR. Therefore, alternative approaches were used: CD and DPP. The data were analyzed using a multivariate curve resolution (MCR) approach, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. The CD study confirmed that the binding of Cd 2+ induces important conformational changes in the structure of the peptidic complex, including the formation of a binuclear cluster. The DPP results obtained at various Cd 2+ -to-peptide concentration ratios and pH values, under conditions where electrode adsorption is low, if not negligible, indicated the formation of different Cd 2+ –peptide complexes, and a scheme for the electrochemical reduction of the complexed Cd 2+ ions is proposed. These results show that the application of MCR to complex data, such as those from DPP, allows to reach valuable information which is not possible to be obtained by univariate approaches.
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zinc binding properties of the c terminal hexapeptide lys cys thr cys cys ala from mouse metallothionein analysis by Differential Pulse Polarography and multivariate curve resolution
Analytica Chimica Acta, 1999Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The zinc-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys–Cys–Thr–Cys–Cys–Ala, were studied by Differential Pulse Polarography (DPP) with a recently proposed multivariate curve resolution (MCR) method, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. From DPP results obtained at different Zn 2+ -to-peptide concentration ratios and at different pH values, the formation of different Zn 2+ –peptide complexes is deduced, and a scheme for the electrochemical reduction of the complexed Zn 2+ ions is proposed. Two complexes have been detected: the first one is formed at low Zn-to-FT concentration ratios and shows a 1:2 Zn:FT stoichiometry; at higher ratios a second Zn 2+ is incorporated yielding a Zn 2 FT 2 complex which probably contains a binuclear cluster.
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study of the zinc binding properties of glutathione by Differential Pulse Polarography and multivariate curve resolution
Journal of Inorganic Biochemistry, 1998Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The complexation between Zn 2+ and glutathione (GSH), in borate buffer, is studied by Differential Pulse Polarography (DPP). Data obtained at pH 8.5 from a titration of Zn 2+ by GSH, i.e. at different GSH-to-Zn 2+ concentration ratios have been analyzed by a recently proposed multivariate curve resolution method. DPP signals obtained within a wide pH range, but at fixed 1.25:1 GSH-to-Zn 2+ concentration ratios, have been resolved individually at each pH value. Results from both sets of experiments can be explained with a complexation model involving the formation of a predominant complex, with a stoichiometry of 2:2 GSH : Zn 2+ .This result is in contrast with those for the Cd 2+ –GSH systems, where two complexes, 2:1 and 2:2 GSH : Cd 2+ , were detected. A scheme for the global electrode process is given.
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the electrochemical behaviour of cd zn thioneins depending on the solution ph using Differential Pulse Polarography
Analytica Chimica Acta, 1995Co-Authors: Consuelo Ruiz, Jesús Mendieta, Adela Rosa RodriguezAbstract:The electrochemical behaviour of Cd,Zn thioneins (MT) from rabbit liver and horse kidney with respect to solution pH at the dropping mercury electrode was studied using Differential Pulse Polarography. The equilibrium M + T ⇆ MT concerning the formation of metallothionein from their metal depleted form for assessing the possibility of reproducing the same original molecule was investigated as a function of pH, going from basic to acid solutions and vice versa. The equilibrium is reversible and dissociation and association are quickly reached. Consequently the apothionein, metallothionein free of metal ions and exhibiting a mainly random-coil structure, in acid solution is still able to maintain its metal binding capability and in neutral or basic solution to complex metal ions through its thiol groups. However, the polarographic response from acid to basic solution is not the same as for the variation of pH in the opposite direction. It is possible that the reconstituted Cd, Zn thionein possesses properties and characteristics which are different to their native form. The apparent stability constants of the complexes CdT, ZnT and HgT were estimated at different pH values. The order of affinity of the metal ions to the thionein is well determined: KHgT ⪢ KCdT > KZnT.
Adela Rosa Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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study of complexing properties of the α metallothionein domain with cadmium and or zinc using Differential Pulse Polarography
Analytica Chimica Acta, 2000Co-Authors: Marta Dabrio, Adela Rosa RodriguezAbstract:Abstract A study of the complexing properties of the α-metallothionein domain with cadmium and/or zinc was performed at pH 8, using Differential Pulse Polarography. The applied method allows one to distinguish between the chemical form of the compound, free metal ions and complexes with the α-domain as well as providing evidence that different forms of complexation exist. This technique was used to monitor changes of different species as a function of different parameters. Polarographic results have been compared with those obtained by electrospray ionisation mass spectrometry providing the molecular mass of compounds at different proportions of metal ions to the α-domain, under similar experimental conditions. The α-domain is capable of complexing cadmium and/or zinc, separately or after simultaneous additions of metal ions. In the case of binary mixtures, Cd+α or Zn+α pure complexes are formed, whereas in the case of tertiary mixtures α+[Cd+Zn] mixed cadmium and zinc complexes prevail. When one of the two ions is added to a solution containing the α-domain complexed with the other cation, it is incorporated into the molecule resulting in a reorganisation, which is illustrated by changes in the polarographic responses. Two different conditions can be clearly distinguished: an excess of ligand and when the metal ions are in excess. For these two conditions two different and characteristic features of polarograms were obtained. So, several stable forms of cadmium and zinc complexation with the α-domain exist, depending on the composition of the solution. The combination of results obtained using two different techniques was very useful for the assignment of different cadmium and zinc electrochemical responses.
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characterisation of human adult kidney cd zn metallothioneins by Differential Pulse Polarography
Bioelectrochemistry and Bioenergetics, 1998Co-Authors: Oscar Nieto, Godelieve Hellemans, Guy Bordin, Marc De Ley, Adela Rosa RodriguezAbstract:Abstract Studies on electrochemical characterisation for the three isoforms of human adult kidney (HAK) Cd,Zn–metallothioneins, labelled MT-0, MT-1 and MT-2, have been performed using Differential Pulse Polarography. Two peaks attributed to the reduction of complexed Cd(II) with MTs as well as two peaks attributed to the reduction of Zn(II) complexed with MTs have been detected, which indicates that two different co-ordination forms for Cd(II) and for Zn(II) with MTs exist. The three isoforms exhibit a similar electrochemical behaviour. Studies on the influence of zinc and cadmium additions as well as on the variation of the solution pH have been carried out. The association and dissociation equilibria of zinc and cadmium with MTs are reversible in the studied pH range (4 or 6–10). The apparent association constants have been evaluated. The electrochemical behaviour of human adult kidney MTs is similar to that found with other mammalian human MTs previously studied.
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characterisation of human foetal liver zn metallothioneins using Differential Pulse Polarography
Talanta, 1998Co-Authors: Oscar Nieto, Godelieve Hellemans, Guy Bordin, Marc De Ley, Adela Rosa RodriguezAbstract:Abstract A study on electrochemical characterisation of three isoforms of human foetal liver Zn-metallothioneins, labelled MT-0, MT-1 and MT-2, has been performed by using Differential Pulse Polarography (DPP). Two different peaks, attributed to two different Zn complexes with metallothioneins, have been detected. The electrochemical behaviour is similar for the three studied isoforms. Studies on the addition of Cd 2+ and Zn 2+ as well as studies as a function of pH have been carried out. The association and dissociation equilibria of metal ions with MTs are reversible in the studied pH range. The behaviour of Zn complexes in human foetal liver Zn-metallothioneins is comparable to the Cd complexes obtained using other mammalian Cd, Zn-metallothioneins, particularly as a function of pH.
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characterisation of human metallothioneins from foetal liver and adult kidney using Differential Pulse Polarography
Analytica Chimica Acta, 1997Co-Authors: Consuelo Ruiz, Adela Rosa RodriguezAbstract:Abstract The electrochemical behaviour of four human metallothioneins (MT) from foetal liver and adult kidney with respect to solution pH as well as the influence of the addition of cadmium and/or zinc were studied using Differential Pulse Polarography. The complexation equilibrium of dissociation and the formation from their metal depleted form was investigated, going from basic to acid solution and vice versa. The stability of these human MTs with respect to changes in the pH of the solution is low. In fact, the complexation equilibrium is not reversible and consequently, the protein, at acid pH, is denatured and the metal binding capacity to complex the cations through the thiol groups is lost. In the case of some of these MTs two different electrochemical responses due to the reduction of complexed Cd(II), as well as to the Zn(II) complexes were distinguished. The predominance of each of these two species for both cations seems to depend on the total concentration, on the ratio between zinc and cadmium concentrations and on the solution pH. In each of the molecules studied, the addition of zinc provokes the transformation of the peak attributed to the Cd-Thionein complex CdT, initially found in the native MT, into another form, CdT′, having different characteristics to the initial one. The MTs are able to incorporate the added metal ions into their molecule. This implies a new reorganisation of the initial molecule in which both cadmium and zinc complexes are involved. The apparent stability constants of the Cd-MT, Zn-MT and Hg-MT complexes were estimated at different pH values.
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study of the additions of cadmium and zinc to the cadmium zinc metallothioneins using Differential Pulse Polarography influence of the ph
Analytica Chimica Acta, 1996Co-Authors: Consuelo Ruiz, Adela Rosa RodriguezAbstract:Abstract The binding properties and metal ion exchanges of Cd, Zn Metallothioneins (MT) from rabbit liver and horse kidney were studied using Differential Pulse Polarography. The influence of the additions of cadmium or/and zinc to the non-saturated MT was investigated. The addition of cadmium does not remove the zinc initially bound to the protein, as one would expect from the values of stability constants of CdT and ZnT complexes, but produces the splitting of the peak attributed to the Cd-thionein complex into two: one corresponding to the initial one, CdT, and another peak, CdT', at a less cathodic potential. The addition of zinc provokes the transformation of the CdT peak, found for the native MT, into CdT'. Assuming that cadmium forms two complexes with the thionein the equilibrium between these two species CdT /ai CdT' was studied as a function of added metal ion concentration and of the solution pH. The pH plays a very important role in the stabilization of each of the two cadmium complexes. All ion exchange equilibria are quickly reached.
A Monjonell - One of the best experts on this subject based on the ideXlab platform.
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Complexation of cadmium by the C-terminal hexapeptide Lys-Cys-Thr-Cys-Cys-Ala from mouse metallothionein: study by Differential Pulse Polarography and circular dichroism spectroscopy with multivariate curve resolution analysis
Analytica Chimica Acta, 1999Co-Authors: Jesús Mendieta, M.s Dı́az-cruz, A Monjonell, R. Tauler, Miquel EstebanAbstract:Abstract The cadmium-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys-Cys-Thr-Cys-Cys-Ala, were studied by circular dichroism spectroscopy (CD), Differential Pulse Polarography (DPP) and 113 Cd-nuclear magnetic resonance (NMR). The structure of the multiple cadmium binding sites could not be determined by 113 Cd-NMR because of the insolubility of the Cd–peptide samples at the high concentrations required for NMR. Therefore, alternative approaches were used: CD and DPP. The data were analyzed using a multivariate curve resolution (MCR) approach, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. The CD study confirmed that the binding of Cd 2+ induces important conformational changes in the structure of the peptidic complex, including the formation of a binuclear cluster. The DPP results obtained at various Cd 2+ -to-peptide concentration ratios and pH values, under conditions where electrode adsorption is low, if not negligible, indicated the formation of different Cd 2+ –peptide complexes, and a scheme for the electrochemical reduction of the complexed Cd 2+ ions is proposed. These results show that the application of MCR to complex data, such as those from DPP, allows to reach valuable information which is not possible to be obtained by univariate approaches.
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zinc binding properties of the c terminal hexapeptide lys cys thr cys cys ala from mouse metallothionein analysis by Differential Pulse Polarography and multivariate curve resolution
Analytica Chimica Acta, 1999Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The zinc-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys–Cys–Thr–Cys–Cys–Ala, were studied by Differential Pulse Polarography (DPP) with a recently proposed multivariate curve resolution (MCR) method, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. From DPP results obtained at different Zn 2+ -to-peptide concentration ratios and at different pH values, the formation of different Zn 2+ –peptide complexes is deduced, and a scheme for the electrochemical reduction of the complexed Zn 2+ ions is proposed. Two complexes have been detected: the first one is formed at low Zn-to-FT concentration ratios and shows a 1:2 Zn:FT stoichiometry; at higher ratios a second Zn 2+ is incorporated yielding a Zn 2 FT 2 complex which probably contains a binuclear cluster.
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study of the zinc binding properties of glutathione by Differential Pulse Polarography and multivariate curve resolution
Journal of Inorganic Biochemistry, 1998Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The complexation between Zn 2+ and glutathione (GSH), in borate buffer, is studied by Differential Pulse Polarography (DPP). Data obtained at pH 8.5 from a titration of Zn 2+ by GSH, i.e. at different GSH-to-Zn 2+ concentration ratios have been analyzed by a recently proposed multivariate curve resolution method. DPP signals obtained within a wide pH range, but at fixed 1.25:1 GSH-to-Zn 2+ concentration ratios, have been resolved individually at each pH value. Results from both sets of experiments can be explained with a complexation model involving the formation of a predominant complex, with a stoichiometry of 2:2 GSH : Zn 2+ .This result is in contrast with those for the Cd 2+ –GSH systems, where two complexes, 2:1 and 2:2 GSH : Cd 2+ , were detected. A scheme for the global electrode process is given.
M S Diazcruz - One of the best experts on this subject based on the ideXlab platform.
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zinc binding properties of the c terminal hexapeptide lys cys thr cys cys ala from mouse metallothionein analysis by Differential Pulse Polarography and multivariate curve resolution
Analytica Chimica Acta, 1999Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The zinc-binding properties of the C-terminal hexapeptide of mouse metallothionein I, Lys–Cys–Thr–Cys–Cys–Ala, were studied by Differential Pulse Polarography (DPP) with a recently proposed multivariate curve resolution (MCR) method, based on factor analysis techniques, which allows the identification of the signal corresponding to different metal ions bound in different chemical environments. From DPP results obtained at different Zn 2+ -to-peptide concentration ratios and at different pH values, the formation of different Zn 2+ –peptide complexes is deduced, and a scheme for the electrochemical reduction of the complexed Zn 2+ ions is proposed. Two complexes have been detected: the first one is formed at low Zn-to-FT concentration ratios and shows a 1:2 Zn:FT stoichiometry; at higher ratios a second Zn 2+ is incorporated yielding a Zn 2 FT 2 complex which probably contains a binuclear cluster.
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study of the zinc binding properties of glutathione by Differential Pulse Polarography and multivariate curve resolution
Journal of Inorganic Biochemistry, 1998Co-Authors: M S Diazcruz, Jesús Mendieta, A Monjonell, Roma Tauler, Miquel EstebanAbstract:Abstract The complexation between Zn 2+ and glutathione (GSH), in borate buffer, is studied by Differential Pulse Polarography (DPP). Data obtained at pH 8.5 from a titration of Zn 2+ by GSH, i.e. at different GSH-to-Zn 2+ concentration ratios have been analyzed by a recently proposed multivariate curve resolution method. DPP signals obtained within a wide pH range, but at fixed 1.25:1 GSH-to-Zn 2+ concentration ratios, have been resolved individually at each pH value. Results from both sets of experiments can be explained with a complexation model involving the formation of a predominant complex, with a stoichiometry of 2:2 GSH : Zn 2+ .This result is in contrast with those for the Cd 2+ –GSH systems, where two complexes, 2:1 and 2:2 GSH : Cd 2+ , were detected. A scheme for the global electrode process is given.