Native and denatured forms of proteins can be discriminated at edge plane carbon electrodes
ABSTRACT In an attempt to develop a label-free electrochemical method for detection of changes in protein structures based on oxidizability of tyrosine and tryptophan residues we tested different types of carbon electrodes. We found that using edge plane pyrolytic graphite electrode (EPGE) we can discriminate between native and denatured forms of human serum albumin (HSA) and of other proteins, such as bovine and chicken serum albumin, aldolase and concanavalin. Treatment of natively unfolded α-synuclein with 8 M urea resulted only in a small change in the tyrosine oxidation peak, in a good agreement with absence of highly ordered structure in this protein. Using square wave voltammetry with EPGE we were able to follow the course of HSA denaturation at different urea concentrations. The electrochemical denaturation curve agreed reasonably well with that based on intrinsic fluorescence of tyrosine and tryptophan. It can be expected that the electrochemical method will be applicable to a large number of proteins and may become useful in biomedicine and proteomics.
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ABSTRACT: We introduce the concept of screen-printed back-to-back electroanalytical sensors where in this facile and generic approach, screen-printed electrodes are printed back-to-back with a common electrical connection to the two working electrodes with the counter and reference electrodes for each connected in the same manner as a normal “traditional” screen-printed sensor would be. This approach utilises the usually redundant back of the screen-printed sensor, converting this “dead-space” into a further electrochemical sensor which results in improvements in the analytical performance. In the use of the back-to-back design, the electrode area is consequently doubled with improvements in the analytical performance observed with the analytical sensitivity (gradient of a plot of peak height/analytical signal against concentration) doubling and the corresponding limit-of-detection being reduced. We also demonstrate that through intelligent electrode design, a quadruple in the observed analytical sensitivity can also be realised when double microband electrodes are used in the back-to-back configuration as long as they are placed sufficiently apart such that no diffusional interaction occurs. Such work is generic in nature and can be facilely applied to a plethora of screen-printed (and related) sensors utilising the commonly overlooked redundant back of the electrode providing facile improvements in the electroanalytical performance.The Analyst 09/2014; 139(21). DOI:10.1039/C4AN01501K · 3.91 Impact Factor
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ABSTRACT: In the case of disruption of Hcy metabolism, the blood level of Hcy increases and it causes particularly the cardiovascular diseases, cancer, dementia and Parkinson’s disease. Thus, the sensitive analysis of Hcy levels in biological fluids is very important. Hcy analysis was performed herein using very practical and cost-effective protocol using differential pulse voltammetry and graphite electrode. Detection limit of Hcy was found to be 1.21 µM in the linear range from 2 µM to 20 µM. The electrochemical Hcy detection in artificial urine medium was also successfully performed even in the presence of L-Cysteine, L-Methionine and Glutathione.Electroanalysis 08/2014; 26(9). DOI:10.1002/elan.201400203 · 2.82 Impact Factor
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ABSTRACT: Protein catalyzed hydrogen evolution reaction at mercury-containing electrodes controlled by constant-current chronopotentiometric stripping (CPS) is representing a new tool useful in protein research. The resulting CPS peak H is sensitive to changes in the protein structure and its amino acid composition. Besides CPS, cyclic voltammetry appears to be useful for study of poly(amino acids) as an intermediate model system between peptides and macromolecular proteins. Here we show that similarly as arginine in polyarginine and lysine in polylysine also histidine residues in polyhistidine contribute to the catalysis of hydrogen evolution under the given conditions. Peak potentials of individual poly(amino acids) are different and depend on the type of amino acid residues.Electroanalysis 09/2013; 25(9). DOI:10.1002/elan.201300170 · 2.82 Impact Factor