The electrochemical behaviour of Cd,Zn thioneins depending on the solution pH using differential pulse polarography

Ruiz, Consuelo; Mendieta, Jesús; Rodríguez, A. R.

doi:10.1016/0003-2670(94)00607-n

Cited by 32 publications

(17 citation statements)

References 4 publications

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“…In this figure all peaks which could be found in binary mixtures are presented. The polarographic peaks have been assigned in accordance with former studies on Cd, ZnMT [8][9][10][11][12][13][14][15][16] and on the cadmium and zinc complexed with FT using DPP [18,19,[21][22][23]. Peaks labelled β(Cd) and β(Zn) have been attributed to the oxidation of the mercury electrode in the presence of thiol groups complexed by cadmium and zinc, respectively.…”

Section: Resultssupporting

confidence: 80%

“…These values are comparable to those obtained for Cd, ZnMT of different origin [8,9,11] and for M-FT complexes [18][19][20], M being Cd, Zn or Hg. Even if the assumption on which this estimation is based can be considered as only approximate, the stability constants of the β domain of MT with different metal ions have been estimated here for the first time.…”

Section: Estimation Of Apparent Stability Constants β-Msupporting

confidence: 88%

“…In this figure, the new peak labelled Cdβ' is shown and is attributed to the reduction of cadmium complexed by the β domain in a different complexation form to the Cdβ one. This new peak is labelled Cdβ' by analogy with peaks named CdT and CdT' in the study of MT [8][9][10][11][12][13][14][15][16] and CdFT and CdFT' obtained with the peptidic fragment FT in the presence of cadmium and/or zinc [17][18][19][20][21][22][23][24][25] in previous electrochemical works. Peaks have been resolved as mentioned and it is necessary to point out that, when Zn 2+ is in excess (Fig.…”

Section: Resultsmentioning

confidence: 89%

“…Peaks labelled Cdβ, Znβ' and Znβ are due to the reduction of metal ions complexed by the peptide. The electrochemical reactions are described elsewhere [9,14].…”

Section: Resultsmentioning

confidence: 99%

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Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Dabrio¹,

Rodríguez²

2000

Analusis

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Mammalian metallothioneins (MT) containing 61 amino acids, of which 20 are cysteine have a structure comprising of two clusters. The α clusters correspond to the C terminal domain of residues 31-61 involving eleven cysteinic residues and the β cluster corresponds to the N-terminal domain of residues 1-30 with nine cysteine residues. All twenty cysteines participate in metal binding. While in the case of MT, their structure and characteristics have been studied using a great variety of analytical methods [1][2][3][4][5][6][7], relatively few studies have been performed with the α and β clusters separately probably due to the difficulties associated with their obtention. In fact these two domains are usually obtained by synthesis using either solid-phase and fragmentcondensation techniques or isolated by proteolysis of metallothioneins of different origin. Nevertheless the use of chemically synthesised and well-characterised separate α and β domains could be very interesting for the study of their metal binding properties and therefore contribute to the understanding of the behaviour of the entire MT.The aim of this research is the systematic study of the complexing properties of the β MT domain with cadmium and/or zinc using electroanalytical methods. These methods have been widely used by our team for the investigation of MT [8][9][10][11][12][13][14][15][16] and related molecules such as the peptidic fragment Lys-Cys-Thr-Cys-Ala (56-61) MT-1 (FT) alone and in the presence of cadmium and/or zinc [17][18][19][20][21][22][23][24][25]. In the case of MT and related molecules, the aminoacid chain is electroactive due to the presence of thiol groups. Moreover, the reduction of the cations, cadmium and zinc, is electrochemically reversible at the mercury electrode and, hence it is possible to obtain three different responses simultaneously for the sample under a given set of experimental conditions. In addition, the electrochemical response depends on the chemical form of the element and allows one to monitor the changes of the different species in solution as a function of different parameters.The β domain has been isolated using different methods [3,7] and its binding properties have been investigated using mainly spectroscopic methods [3,7,[26][27][28][29][30][31][32][33]. The synthesised peptide used in this work has been purchased from the Biochemistry Institute of Zurich University. The purity of this molecule was checked by both Dr. Klauser's team from Zurich University and our team using electrospray ionisation mass spectrometry (ESI-MS) [34,35].The binding properties have been studied, using differential pulse polarography, with different types of additions of metal ions to the apo-β domain and the inverted addition of the β MT domain to metal ions, the gradual addition of metal ions separately and the addition of both cations simultaneously.

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Section: Resultssupporting

confidence: 80%

Section: Estimation Of Apparent Stability Constants β-Msupporting

confidence: 88%

Section: Resultsmentioning

confidence: 89%

“…Peaks labelled Cdβ, Znβ' and Znβ are due to the reduction of metal ions complexed by the peptide. The electrochemical reactions are described elsewhere [9,14].…”

Section: Resultsmentioning

confidence: 99%

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Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Dabrio¹,

Rodríguez²

2000

Analusis

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“…In all cases, the coordination number (m) of Zn(II) is greater than that of Cd. Anyway, all these values are comparable to those obtained by DPP for different MTs which contain a very variable proportion of Cd and Zn in the molecule [12,14,15]. corresponding to the reduction of complexed Cd is produced at the pH for which the Zn(II) is incorporated or dissociated to the molecule and, consequently, the CdFT H peak is detected.…”

Section: In¯uence Of the Solution Ph In The Complexationsupporting

confidence: 69%

Complexation Properties of the Metallothionein Fragment Lys-Cys-Thr-Cys-Cys-Ala [56-61] MT I with Zinc and Cadmium Using Square Wave Voltammetry

Nieto

Rodríguez²

1999

Electroanalysis

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An electrochemical study using square wave voltammetry of the complexing properties of the peptide Lys-Cys-Thr-Cys-Cys-Ala [56±61] MT 1 (FT), a part of the metallothionein structure, with cadmium and zinc was performed. The applied technique allows one to obtain wellde®ned peaks corresponding to the free metal ions as well as providing evidence that different forms of coordination of Cd(II) and Zn(II) with the peptide exist. FT is capable of complexing Cd 2 and Zn 2 separately in a concentration equal to FT, obtaining complexes with a ratio of 1 : 1. However, the total metal ion concentration bound to the FT is higher when both cations are simultaneously present. The maximum total concentration that can be complexed with FT is a ratio of [Zn] : [Cd] : [FT] like 0.6 : 1.0 : 1.0 which leads to the ratio of Zn 4 Cd 7 S 21 , comparable to that of the metallothionein structure. The coordination of Cd(II) with FT not only depends on the Cd : FT ratio, but also on the proportion in which Zn(II) is added. However, the Zn(II) complexes are not affected by the presence of Cd-FT complexes in solution. The complexation equilibrium was investigated going from acid to basic solutions and viceversa. From the slopes of the variation E p f (pH), the number of thiol groups at which the cations are bound were evaluated. This study allows us to enable comparisons between the behavior of [Zn] : [Cd] : [FT] with that of Cd,Zn metallothioneins.

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Polarographic Behavior of Metal Phytochelatin Complexes

Scarano

Morelli

1998

Electroanalysis

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The polarographic characteristics of metal-phytochelatin complexes (Me-PC) extracted from the marine alga Phaeodactylum tricornutum were investigated by the use of differential pulse polarography (DPP) at dropping mercury electrode (DME). Four metal-phytochelatin complexes differing for the metal bound, namely Cd-, Pb-, Zn-and Cu-PC, were studied, and their polarographic behavior was compared with that of Cd,Znthionein and Zn-thionein of mammalian origin. The polarographic characteristics of Me-PC exhibit a dependence on the metal bound to the peptides and on the pH of the solution. Both the organic and inorganic part of Me-PC are electroactive and give polarographic responses depending on their chemical form in solution. Dissociation and formation processes were investigated. The order of stability of the complexes was KZn¹PC . The same electrochemical mechanisms were found to characterize both the polarographic behavior of metallothioneins and metal-phytochelatin complexes.

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The electrochemical behaviour of Cd,Zn thioneins depending on the solution pH using differential pulse polarography

Cited by 32 publications

References 4 publications

Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Complexing properties of the b metallothionein domain with cadmium and/or zinc, studied by differential pulse polarography

Complexation Properties of the Metallothionein Fragment Lys-Cys-Thr-Cys-Cys-Ala [56-61] MT I with Zinc and Cadmium Using Square Wave Voltammetry

Polarographic Behavior of Metal Phytochelatin Complexes

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