Electrochemical investigation of binding sites of plantacyanin: blue, copper-containing protein of plants

Electrochemical Profiling of Plants

The profiling, or fingerprinting, of distinct varieties of the Plantae kingdom is based on the bioactive ingredients, which are systematically segregated to perform their detailed analysis. The secondary products portray a pivotal role in defining the ecophysiology of distinct plant species. There is a crucial role of the profiling domain in understanding the various features, characteristics, and conditions related to plants. Advancements in variable technologies have contributed to the development of highly specific sensors for the non-invasive detection of molecules. Furthermore, many hyphenated techniques have led to the development of highly specific integrated systems that allow multiplexed detection, such as high-performance liquid chromatography, gas chromatography, etc., which are quite cumbersome and un-economical. In contrast, electrochemical sensors are a promising alternative which are capable of performing the precise recognition of compounds due to efficient signal transduction. However, due to a few bottlenecks in understanding the principles and non-redox features of minimal metabolites, the area has not been explored. This review article provides an insight to the electrochemical basis of plants in comparison with other traditional approaches and with necessary positive and negative outlooks. Studies consisting of the idea of merging the fields are limited; hence, relevant non-phytochemical reports are included for a better comparison of reports to broaden the scope of this work.

Electrochemical characterization and application of azurin-modified gold electrodes for detection of superoxide

A novel biosensor for superoxide radical (O(2)(*-)) detection based on Pseudomonas aeruginosa azurin immobilized on gold electrode was designed. The rate constant of azurin reduction by O(2)(*-) was found to be 10(5)M(-1)s(-1) in solution and five times lower, i.e., 0.2 x 10(5)M(-1)s(-1), for azurin coupled to gold by 3,3'-dithiobis(sulfosuccinimidylpropionate) (DTSSP). The electron transfer rate between the protein and the electrode ranged from 2 to 6s(-1). The sensitivity of this biosensor to O(2)(*-) was 6.8 x 10(2)Am(-2)M(-1). The response to the interference substances, such as uric acid, H(2)O(2), and dimethylsulfoxide was negligible below 10 microM. The electrode was applied in three O(2)(*-) generating systems: (i) xanthine oxidase (XOD), (ii) potassium superoxide (KO(2)), and (iii) stimulated neutrophil granulocytes. The latter was compared with luminol-amplified chemiluminescence. The biosensor responded to O(2)(*-) in all three environments, and the signals were antagonized by superoxide dismutase.

The influence of promoter and of electrode material on the cyclic voltammetry of Pisum sativum plastocyanin

The reversible cyclic voltammetry of pea plastocyanin (Pisum sativum) was studied with a wide range of electrodes: edge-oriented pyrolytic graphite (PGE), glassy carbon (GCE), gold (Au) and platinum (Pt) electrodes. Plastocyanin was coated onto the electrode surface by exploiting the electrostatic interaction between the negatively charged protein and a wide range of positively charged promoters. The effect of the redox response with an extended range of promoters, including poly-L-lysine, polymyxin B, neomycin, tobramycin, geneticin, spermine and spermidine, were included in this study. The resulting cyclic voltammograms reveal that the observed midpoint potential for plastocyanin can be shifted significantly depending on the choice of promoter. The stability of the negatively charged plastocyanin-promoter layer on an electrode was gauged by the rate of bulk diffusion of the protein from the immobilised film into the solution. Reversible cyclic voltammograms were obtained using edge-oriented pyrolytic graphite (PGE) and glassy carbon electrodes (GCE) with all promoters; however, platinum and gold electrodes were unable to sustain a defined redox response. The combination of pyrolytic graphite electrode/poly-L-lysine/plastocyanin was found to be the most stable combination, with a redox response which remained well defined in solution for more than 1 h at pH 7.0. The midpoint potentials obtained in this manner differed between the two graphite electrodes PGE and GCE using poly-L-lysine as the promoter. This effect was in addition to the expected pH dependence of the midpoint potential for plastocyanin and the results indicated that the pK(a) for plastocyanin on PGE was 4.94 compared to that on GCE of 4.66. It is concluded that both the electrode material and the nature of the promoter can influence the position of the redox potentials for proteins measured in vitro. This study extends the range of biogenic promoters used in combination with electrode materials. Thus, we can begin to develop a more comprehensive understanding of electrode-protein interactions and draw conclusions as to metalloprotein function, in vivo. To support these studies, we have sought information as to the nature of the electrode/promoter/protein interaction using scanning tunneling microscopy (STM) to study both the promoter and the plastocyanin protein on a gold surface.