ИСТИНА

Proteins play a vital role in various life processes on the earth and, hence, can be used in clinical medicine. Electrochemical activity of protein molecules is based on theire two main structural characteristics: (i) redox co-factors contaning metal ions (Fe3+, Cu2+, Zn2+, Ni2+) or/and (ii) the pyrroloquinoline or flavin domain [1] and (ii) electroactive amino acid residues [2]. In view of this, direct redox activity of proteins was investigated by use of carbon screen printed electrodes (SPE). Oxidation of proteins was observed in the same range of potentials that was characteristic for cysteine (Cys), tryptophan (Trp) and tyrosine (Tyr). Correlation between the amount of Cys, Trp and Tyr residues on the molecular surface and the registered electrochemical signal was established by bioinformatics analysis. Therefore, each protein is electrochemically active. This phenomenon opens up the possibility to perform the direct analysis of proteins of interest and to determine electrochemically their interactions, complexing, folding-unfolding and posttranslational modifications. Protein oxidation can be used as a simple and fast approach for total protein measurement. Undiluted human plasma and serum samples that are rich in proteins appear to be promising objects for electrochemical analysis and “profiling”. For example, cardiac myoglobin was detected in human plasma by direct electron transfer between the Fe(III)-heme and the SPE that was modified with metal nanoparticles stabilized by didodecyldimethylammonium bromide and antibodies. [3] As a further step, a direct antibodies-free electrochemical approach for acute myocardial infarction diagnosis has been developed using a combination of the electrochemical assay of plasma samples with chemometrics. [4] (Financial support was by Ministry of Education and Science of the Russian Federation, Contract № 8806). [1] A. A. Karyakin, Principles of direct (mediator free) bioelectrocatalysis, Bioelectrochemistry 88 (2012) 70. [2] V. Brabec, V. Mornstein, Electrochemical behaviour of proteins at graphite electrodes: I. Electrooxidation of proteins as a new probe of protein structure and reactions, Biochimica et Biophysica Acta - Protein Structure 625 (1980) 43. [3] E. V. Suprun, A. L. Shilovskaya, A. V. Lisitsa, T. V. Bulko, V. V. Shumyantseva, A. I. Archakov, Electrochemical Immunosensor Based on Metal Nanoparticles for Cardiac Myoglobin Detection in Human Blood Plasma, Electroanalysis 23 (2011) 1051. [4] E. V. Suprun, A. A. Saveliev, G. A. Evtugyn, A V. Lisitsa, T. V. Bulko, V. V. Shumyantseva, A. I. Archakov, Electrochemical approach for acute myocardial infarction diagnosis based on direct antibodies-free analysis of human blood plasma, Biosensors and Bioelectronics 33 (2012) 158.