Study of the additions of cadmium and zinc to the cadmium, zinc metallothioneins using differential pulse polarography Influence of the pH

Ruiz, Consuelo; Rodríguez, A. R.

doi:10.1016/0003-2670(96)00025-6

Cited by 28 publications

(17 citation statements)

References 6 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%

“…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%

“…8A and 8B, polarogramme b). Whereas for several MT the equilibrium CdT ↔ CdT' is reversible and quickly reached [10], in the case of β:Cd:Zn mixtures the equilibrium between Cdβ and Cdβ' is not reversible and, hence, Cdβ' is not detected when the pH is readjusted to 8; moreover the signals due to the Zn(II) reduction are not observed at more basic pH and are also not detected at the readjusted pH.…”

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 93%

“…In previous DPP studies with MT [10,11,13,16] and with FT:Cd:Zn [19,20,25], the variation of pH has been seen to play an important role in the stability of one of the two cadmium complexes, CdT and CdT', and CdFT and CdFT'; in fact it is possible to provoke a change or to modify the proportion of both complexes by a mere change of the solution pH. When the pH is increased from 8 to 9.5 the transformation of CdT' peak, obtained in the presence of zinc, into the CdT peak occurs.…”

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 95%

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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: Resultsmentioning

confidence: 89%

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 93%

Section: Influence Of the Ph On The Complexation Forms Of Cadmiummentioning

confidence: 95%

See 2 more Smart Citations

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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“…Polarography or voltammetry have been used for detection of metallothioneins in procedures, where sulfur-cobalt complexes are formed and Brdička catalytic waves are measured [12]. Cyclic voltammetry on HMDE has been applied to the study of animal metallothionein of different origin [13] and several studies using differential pulse polarography for mamalian Cd,Zn metallothioneins were performed by Rodríguez and co-workers [14][15][16]. Scarce are studies on plant metallothioneins.…”

Section: Introductionmentioning

confidence: 99%

Voltammetric Methods for Speciation of Plant Metallothioneins

1998

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Cd, Cu and Zn complexes of two synthetically prepared peptides, (g-Glu-Cys) 2 -Gly and (g-Glu-Cys) 3 -Gly, were studied as models of plant metallothioneins by several voltammetric methods. Reduction peak of the complex in which the stechiometric ratio of molar concentrations of Cd(II) and peptide corresponds to coordination of one Cd(II) by four sulfur atoms (E p = ¹814 mV to ¹910 mV, DPV) is suitable for speciation. CSV after adsorption of Cu(I) complex on HMDE is also convenient, and two peaks (E p = ¹817 mV to ¹850 mV and E p = ¹940 mV to ¹953 mV) are attributed to plant MT with Cu(I). Cd and Cu complexes can be distinguished by different dependences for adsorptive accumulation of complexes on HMDE. In both cases the presence of zinc ions interferes with voltammetric speciation. Results of voltammetric studies were applied to the analysis of algal extracts, prepared from alga Chlorella, which was grown in cadmium enriched medium. Successful voltammetric identification of plant metallothionein in this type of material has been performed, in agreement with results from AAS and UV spectroscopy.

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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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Study of the additions of cadmium and zinc to the cadmium, zinc metallothioneins using differential pulse polarography Influence of the pH

Cited by 28 publications

References 6 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

Voltammetric Methods for Speciation of Plant Metallothioneins

Polarographic Behavior of Metal Phytochelatin Complexes

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