Brdička-type processes of cysteine and cysteine-containing peptides on silver amalgam electrodes

Development and Evaluation of Copper Electrodes, Modified with Bimetallic Nanoparticles, to be Used as Sensors of Cysteine-Rich Peptides Synthesized by Tobacco Cells Exposed to Cytotoxic Levels of Cadmium

We report on two new electrochemical sensors which, coupled to differential pulse voltammetry, constitutes a useful tool for diagnosis of heavy metal pollution. The electrochemical sensors AgHgNf/Cu and the AgBiNf/Cu were obtained by deposition of bimetallic particles of AgHg or AgBi on copper electrodes covered with a Nafion (Nf) film, respectively. Micrographs of the electrode's surface showed evenly scattered bimetallic particles, with an approximate diameter of 150 nm, embedded in the Nafion (Nf) film. In order to test the electrodes, the hydrogen evolution signal according to the Brdička reaction was measured for the determination of cysteine-rich peptides (CRp) produced by plants. To check the accuracy of the electrodes, real samples of Nicotiana tabacum cells exposed to cytotoxic levels of cadmium were tested. The AgHgNf/Cu electrode produced detection limits (DLs) of 0.088 µmol L-1 for Cysteine and 0.139µmol L-1 for Glutathione, while for the AgBiNf/Cu electrode DLs were 0.41 µmol L-1 for cysteine and 0.244 µmol L-1 for glutathione. Thus, the new electrodes could be a useful analytical electrochemical system very convenient for fieldwork. The electrodes were capable of direct, accurate, and sensitive detection of synthesized peptides, despite the complex matrix where the Nicotiana tabacum cells were grown.

Evaluation of the Cadmium Accumulation in Tamarillo Cells (Solanum betaceum) by Indirect Electrochemical Detection of Cysteine-Rich Peptides

Long-term cadmium intake can be very dangerous to human health due to its toxic effects. Although people can be contaminated with this element from different sources, contaminated food is probably the most important one. Foods such as vegetables and fruits can become contaminated with cadmium existing in soils, irrigation water, or chemical fertilizers. Some plants produce an excess of cysteine-rich peptides (CRp) when affected by high concentrations of heavy metals such as cadmium, thus indicating the presence of this type of contamination. Among these plants is tamarillo (Solanum betaceum), which is locally known as “tree tomato”. This is a native plant widely consumed in the Ecuadorian Andes because of its abundance, low cost, and high content of vitamin C and fiber. The fact that Solanum betaceum produces CRp upon contamination with heavy metals means that this plant may be able to accumulate heavy metals. If this is the case, the plant can possibly be used as an indicator of metal pollution. The main goals of the present work were to evaluate the possibility of using Solanum betaceum as an indicator of metal contamination in plants and to examine its capability to accumulate metals. Both goals were met by determination of the amounts of CRp produced by Solanum betaceum cells cultivated in vitro in the laboratory under controlled conditions in the presence of different concentrations of cadmium. The CRp determination was carried out by means of electrogeneration of iodine in an iodide solution containing reduced glutathione as a biological thiol model. Solanum betaceum cells were grown in a Murashige and Skoog solution enriched with a 30 g L⁻¹ sugar aqueous solution and 1 mg L⁻¹ 2,4-dichlorophenoxyacetic acid. The results of these experiments confirmed the following: (1) CRp production is a function of the amount of cadmium present as a contaminant up to a limiting value after which cell apoptosis occurs; (2) Solanum betaceum accumulates cadmium; (3) the analytical method used is appropriate for CRp determination; and (4) CRp determination is a valid alternative to detect contamination by heavy metals in plants.

Comparison Study of Voltammetric Behavior of Muscle Relaxant Dantrolene Sodium on Silver Solid Amalgam and Bismuth Film Electrodes

Voltammetric behavior of muscle relaxant dantrolene sodium (DAN) was studied and the voltammetric methods for its determination using polished and mercury meniscus modified silver solid amalgam electrodes (p-AgSAE and m-AgSAE) as well as using bismuth film electrode (BiFE, ex situ plating on GCE) have been proposed. These working electrodes represent the most commonly used alternatives to mercury ones which come wrongfully into disfavor because of alleged toxicity of mercury. Within this work, the obtained results of DAN determination have been completed by corresponding statistical parameters and also some electrochemical characteristics of AgSAEs and BiFE were assessed, especially in comparison with the mercury electrodes.

Alkylsulfanylphenyl derivatives of cytosine and 7-deazaadenine nucleosides, nucleotides and nucleoside triphosphates: synthesis, polymerase incorporation to DNA and electrochemical study

Aqueous Suzuki-Miyaura cross-coupling reactions of halogenated nucleosides, nucleotides and nucleoside triphosphates derived from 5-iodocytosine and 7-iodo-7-deazaadenine with methyl-, benzyl- and tritylsufanylphenylboronic acids gave the corresponding alkylsulfanylphenyl derivatives of nucleosides and nucleotides. The modified nucleoside triphosphates were incorporated into DNA by primer extension by using Vent(exo-) polymerase. The electrochemical behaviour of the alkylsulfanylphenyl nucleosides indicated formation of compact layers on the electrode. Modified nucleotides and DNA with incorporated benzyl- or tritylsulfanylphenyl moieties produced signals in [Co(NH(3))(6)](3+) ammonium buffer, attributed to the Brdička catalytic response, depending on the negative potential applied. Repeated constant current chronopotentiometric scans in this medium showed increased Brdička catalytic response, which suggests the deprotection of the alkylsulfanyl derivatives to free thiols under the conditions.