Frantisek Jelen - Academia.edu (original) (raw)

Papers by Frantisek Jelen

Electrochimica Acta, Feb 1, 2009

Determination of uric acid (UA) levels in body fluids is important for diagnostics and prevention... more Determination of uric acid (UA) levels in body fluids is important for diagnostics and prevention of severe metabolic disorders. Electrochemical determination of the UA relies on an oxidation signal measurable at different carbon-based electrodes. Improvement of the UA electrochemical sensing has usually been attained via various modifications of the electrode surfaces. In this paper we show that a strong enhancement of the UA oxidation signal can be reached by a simple mechanical grinding of the surfaces of glassy carbon or edge plane-oriented pyrolytic graphite electrodes with SiC particles of an optimum size 15 m. In contrast to fine polished electrodes (finally with 1-m particles), the grinded ones exhibited an excellent separation of oxidation signals of ascorbic acid, dopamine (representing most important natural interferents in UA determination), xanthine and hypoxanthine (precursors of UA in purine catabolism), making it possible to detect these substances in a mixture. Enhancement of UA and dopamine (DA) oxidation signals at the grinded electrodes allowed their easy detection at nanomolar levels in up to 10 4 -fold excesses of ascorbic acid. Due to a strong adsorption at the electrode surface, nanomolar concentrations of UA and DA can be determined by ex situ voltammetry. Similarly strong enhancement of oxidation signals was observed for purine nucleobases, guanine and adenine. The grinded electrodes have been tested in analysis of real clinical samples of human serum or urine. An excellent agreement between electrochemical and routine biochemical determination of UA in the biological samples is demonstrated.

Crit Rev Anal Chem, 2002

... Critical Reviews in Analytical Chemistry, 32(2):167–179 (2002) Impedance Analysis of DNA and ... more ... Critical Reviews in Analytical Chemistry, 32(2):167–179 (2002) Impedance Analysis of DNA and DNA–Drug Interactions on Thin Mercury Film Electrodes Stanislav Hason,1,2 Jakub Dvorák,1,2 Frantisek Jelen,2 and Vladimír Vetterl1,2* ...

General Physiology and Biophysics

In the presence of pyridine and other ligands osmium tetroxide binds covalently to pyrimidine bas... more In the presence of pyridine and other ligands osmium tetroxide binds covalently to pyrimidine bases in DNA. Properties of osmium-modified native and denatured calf thymus DNA, and plasmid Co1E1 DNA were investigated by means of differential pulse polarography, absorption spectrophotometry, circular dichroism, agarose gel electrophoresis, and nuclease S1 digestion. A great difference in the reaction kinetics of native and denatured DNAs with osmium, pyridine was observed. On the ground of the slow stepwise reaction kinetics of native DNA in the initial stage of its modification by osmium it has been suggested that the primary reaction sites do not include bases contained in the intact double helix. Osmium binding to sporadic primary reaction sites (represented e.g. by bases in the vicinity of a single-strand break) in native calf thymus DNA resulted in local changes in DNA conformation limited to a close neighbourhood of the binding site. At higher osmium/nucleotide ratios disordering of the DNA structure over a region extending beyond the immediate binding site was observed. With denatured DNA the same type of structure disordering was detected already in the initial stage of the reaction at osmium/nucleotide ratios as low as 0.01. Osmium binding to the supercoiled Co1E1 DNA resulted in its relaxation without nicking and it increased its sensitivity to linearization by cleavage with nuclease S1. The behaviour of Co1E1 DNA has been explained by the formation of a denatured region in the molecule (accompanied by a coupled loss of duplex and superhelical turns). It has been suggested that osmium can be used to label and to visualize distorted regions in the DNA double helix.

General Physiology and Biophysics

It has been shown earlier that the DNA double helix is opened due to a prolonged contact of the D... more It has been shown earlier that the DNA double helix is opened due to a prolonged contact of the DNA molecule with the surface of the mercury electrode. At neutral pH, the opening process is relatively slow (around 100 s), and it is limited to potentials close to -1.2 V (against SCE). The opening of the double helix has been explained by strains in the DNA molecule due to strong repulsion of the negatively charged phosphate residues from the electrode surface where the polynucleotide chain is anchored via hydrophobic bases. Interaction of the synthetic ds polynucleotides with alternating nucleotide sequences /poly(dA-dT) . poly (dA-dT), poly (dA-dU) . poly (dA-dU), poly (dG-dC) . poly (dG-dC)/ and homopolymer pairs /poly (dA) . poly (dT), poly (rA) . poly (rU) and poly (dG) . poly (dC)/ with the hanging mercury drop electrode has been studied. Changes in reducibility of the polynucleotides were exploited to indicate opening of the double helix. A marked difference in the behaviour was observed between polynucleotides with alternating nucleotide sequence and homopolymer pairs: opening of the double-helical structures of the former polynucleotides occurs at a very narrow potential range (<100mV) (region U), while with the homopolymer pairs containing A . T or A . U pairs, the width of this region is comparable to that of natural DNA (>200 mV). In contrast to natural DNA, the region U of homopolymer pairs is composed of two distinct phases. No region U was observed with poly (dG) . poly (dC). In polynucleotides with alternating nucleotide sequence, the rate of opening of the double helix is strongly dependent on the electrode potential in region U, while in homopolymer pairs, this rate is less potential-dependent. It has been assumed that the difference in the behaviour between homopolymer pairs and polynucleotides with alternating nucleotide sequence is due to differences in adsorbability of the two polynucleotide chains in the molecule of a homopolymer pair (resulting from different adsorbability of purine and pyrimidine bases) in contrast to equal adsorbability of both chains in a polynucleotide molecule with alternating nucleotide sequence. It has been shown that the mercury electrode is a good model of biological surfaces (e.g. membranes), and that the nucleotide sequence-dependent opening (unwinding) of the DNA I HMDE LU RED " Ei Fig. 1. Signals applied and responses obtained (A): in differential pulse polarography (DPP) in connection with the dropping mercury electrode (DME) (representing a technique working with small voltage excursion during the drop life time; (B): in linear sweep voltammetry (LSV) in connection with hanging mercury drop electrode (HMDE). (A): in DPP a single voltage pulse (usually of 10-50 mV) is applied to each drop of mercury dropping from the DME in 1-2 s intervals. The voltage ramp is scanned 1-2 mV/s. (B): in LSV, HMDE is kept for a certain time interval í at the initial potential Ei. During this waiting time t, DNA is adsorbed at the electrode and may undergo certain changes in its secondary structure due to its prolonged interaction with the electrode surface. After the waiting time ;, the electrode potential is rapidly changed (usually 0.5-5 V/s) to more negative values at which ss DNA is reduced (Ered). The height of the voltammetric peak 3 is proportional to the amount of ss DNA reduced at the electrode surface, and it serves as an indication of the extent of surface denaturation of ds DNA. (a, d) thermally denatured DNA (b, c, e, f) ds DNA (in the bulk of solution); (c) at a concentration as usual for measurments of denatured DNA (20-30 ug/ml); (ft) at higher concentra tions (300-400 ug/ml) and a high sensitivity of the instrument; (d, f) Ei in the region T (e.g. -0.6 V); (e) Ei in the region U (e.g. -1.2 V), -for regions U and T see Fig. 2.

General Physiology and Biophysics

Osmium tetroxide, 2,2'-bipyridine (Os,bipy) has been widely applied as a probe of the DNA structu... more Osmium tetroxide, 2,2'-bipyridine (Os,bipy) has been widely applied as a probe of the DNA structure. To obtain information about reactivity of DNA bases toward this probe synthetic homopolynucleotides poly(dT), poly(dC), poly(dG) and poly(dA) were treated with Os,bipy and the content of modified bases mea sured by stripping voltammetry and absorption spectrophotometry. After 20 hours' treatment strong modification of poly(dT) and poly(dC) and weak modification of poly(dG) were observed, while no modification was detected in poly(dA). At short incubation times under conditions close to those usually used in probing the DNA structure the extent of poly(dT) modification was more than 10 times higher than that of poly(dC). Thus, in single-stranded DNA Os,bipy reacts with T >> C and G. Due to the fast reaction of thymines with Os,bipy (and osmium tetroxide, pyri dine) these chemicals can be applied in Maxam-Gilbert nucleotide sequencing as agents specific for thymines in single-stranded DNA.

General Physiology and Biophysics

Synthetic homopolyribonucleotides poly(A), poly(U), poly(C), and poly(G), poly(A, G, U), apurinic... more Synthetic homopolyribonucleotides poly(A), poly(U), poly(C), and poly(G), poly(A, G, U), apurinic acid and native and denatured DNA from calf thymus were analyzed by means of cyclic voltammetry (CV) using a hanging mercury drop electrode. It was shown that guanine containing polynucleotides, i.e. poly(G), poly(A, G, U) and DNA yield an anodic peak of guanine in the vicinity of a potential of -0.3 V (against a saturated calomel electrode). The guanine peak appeared only at a sufficiently negative switching potential (about -2 V). The appearance of the guanine peak was conditioned by a reduction of guanine residues in the region of the switching potential and reoxidation of the reduction product in the vicinity of -0.3 V. Native and thermally denatured DNAs were investigated under the conditions of both complete and incomplete coverage of the electrode in various background electrolytes. Both DNA forms yielded anodic CV peaks of guanine with the peak of denatured DNA being always higher than that of native DNA. Irradiation of native DNA with relatively small doses of gamma radiation (5-120 Gy) resulted in an increase of the anodic peak. A comparison of changes induced by gamma radiation in the anodic (guanine) and cathodic (reduction of adenine and cytosine) peaks showed a steeper increase of the cathodic peak as compared to that of the anodic one. It has been concluded that in the given dose range the DNA double-helical structure is mainly damaged in the adenine-thymine rich regions.

Electrochemically active labels have been applied in electrochemical nucleic acid analysis and DN... more Electrochemically active labels have been applied in electrochemical nucleic acid analysis and DNA biosensors (reviewed in 1,2). Electroactive species (covalently coupled to DNA or binding the DNA non-covalently) are employed to improve sensitivity and/or specificity of DNA detection. This may be reached via choosing markers providing reversible and/or catalytic high electron yield signals, occurring at less extreme potentials than irreversible intrinsic DNA reduction (at mercury or solid amalgam electrodes) or oxidation (usually at carbon electrodes) electrochemical responses 1,2 . Osmium tetroxide complexes (Os,L) were for the first time introduced as electroactive DNA markers and chemical probes of DNA structure in the early 1980's (3 and refs. therein). Complexes of OsO 4 with nitrogen ligands such 2,2'-bipyridine (bipy) covalently bind to the 5,6 double bond of the pyrimidine ring (thymine is about 10-fold more reactive than cytosine); purine bases practically do not re...

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1977

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and... more Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribocytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylic acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible --S--S--groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdi6ka's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdi~ka's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can, however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.

Weimar (D.D.lZ.). o3o2-4958 / o/o317-o332 © Elsevier Sequoia S.A.

Sensors (Basel, Switzerland), 2015

Interest in electrochemical analysis of purine nucleobases and few other important purine derivat... more Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications.

Electrochemical DNA Biosensors, 2012

2010 IEEE Sensors, 2010

An innovative electrochemical sensor based on a combination of the elimination voltammetry and ad... more An innovative electrochemical sensor based on a combination of the elimination voltammetry and adsorptive stripping (AdS) techniques with a slightly soluble complex is presented. The test of our approach was aimed at analysis of aminopurines and oxopurines on carbon paste (CPE) and pencil graphite electrodes (PeGE). The voltammetric signals of purine derivatives are amplified: (i) by increasing the surface concentration

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

The electrochemical behaviour of 30 purine and pyrimidine derivatives and of a further 12 derivat... more The electrochemical behaviour of 30 purine and pyrimidine derivatives and of a further 12 derivatives containing sulphur or halogens was studied. It was demonstrated that most of these substances react with the electrode mercury and form sparingly soluble compounds; this phenomenon can be exploited for the determination of purine and pyrimidine derivatives at low concentrations. The relation between the structural formulae of the substances and their ability to yield anodic polarographic currents conditioned by formation of sparingly soluble compounds with mercury was found. The behaviour of adenine and 8-oxyadenine was studied in greater detail by means of differential (DPP) and normal pulse polarography (NPP), d.c. polarography and cathodic stripping voltammetry (CSV). Both substances can be determined with the aid of CSV at concentrations of the order of magnitude of 10 -9 M, while DPP may be used at concentrations three to four orders of magnitude higher. Interactions of some purine and pyrimidine derivatives with Hg(II) ions in homogeneous aqueous solutions were investigated. On the one hand, a correlation was found between the ability of these substances to react with mercury in solution and form precipitates, and, on the other hand, to yield anodic polarographic currents.

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

... 128 (1981)Elsevier Sequoia SA, Lausanne --- Printed in The Netherlands497444 -- ELECTROCHEMIC... more ... 128 (1981)Elsevier Sequoia SA, Lausanne --- Printed in The Netherlands497444 -- ELECTROCHEMICAL ANALYSIS OF POLYNUCLEOTIDES *EMIL PALE~EK, EMILIE ... It does not react, however, withbases incorporated in an intact Watson--Crick DNA double helix; this agent ...

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

Closed duplex (cd) and open circular (oc) forms of DNA of the plasmid Col E1 were studied by mean... more Closed duplex (cd) and open circular (oc) forms of DNA of the plasmid Col E1 were studied by means of a.c. and differential pulse polarography (d.p.p.).

Electrochimica Acta, Feb 1, 2009

Determination of uric acid (UA) levels in body fluids is important for diagnostics and prevention... more Determination of uric acid (UA) levels in body fluids is important for diagnostics and prevention of severe metabolic disorders. Electrochemical determination of the UA relies on an oxidation signal measurable at different carbon-based electrodes. Improvement of the UA electrochemical sensing has usually been attained via various modifications of the electrode surfaces. In this paper we show that a strong enhancement of the UA oxidation signal can be reached by a simple mechanical grinding of the surfaces of glassy carbon or edge plane-oriented pyrolytic graphite electrodes with SiC particles of an optimum size 15 m. In contrast to fine polished electrodes (finally with 1-m particles), the grinded ones exhibited an excellent separation of oxidation signals of ascorbic acid, dopamine (representing most important natural interferents in UA determination), xanthine and hypoxanthine (precursors of UA in purine catabolism), making it possible to detect these substances in a mixture. Enhancement of UA and dopamine (DA) oxidation signals at the grinded electrodes allowed their easy detection at nanomolar levels in up to 10 4 -fold excesses of ascorbic acid. Due to a strong adsorption at the electrode surface, nanomolar concentrations of UA and DA can be determined by ex situ voltammetry. Similarly strong enhancement of oxidation signals was observed for purine nucleobases, guanine and adenine. The grinded electrodes have been tested in analysis of real clinical samples of human serum or urine. An excellent agreement between electrochemical and routine biochemical determination of UA in the biological samples is demonstrated.

Crit Rev Anal Chem, 2002

... Critical Reviews in Analytical Chemistry, 32(2):167–179 (2002) Impedance Analysis of DNA and ... more ... Critical Reviews in Analytical Chemistry, 32(2):167–179 (2002) Impedance Analysis of DNA and DNA–Drug Interactions on Thin Mercury Film Electrodes Stanislav Hason,1,2 Jakub Dvorák,1,2 Frantisek Jelen,2 and Vladimír Vetterl1,2* ...

General Physiology and Biophysics

In the presence of pyridine and other ligands osmium tetroxide binds covalently to pyrimidine bas... more In the presence of pyridine and other ligands osmium tetroxide binds covalently to pyrimidine bases in DNA. Properties of osmium-modified native and denatured calf thymus DNA, and plasmid Co1E1 DNA were investigated by means of differential pulse polarography, absorption spectrophotometry, circular dichroism, agarose gel electrophoresis, and nuclease S1 digestion. A great difference in the reaction kinetics of native and denatured DNAs with osmium, pyridine was observed. On the ground of the slow stepwise reaction kinetics of native DNA in the initial stage of its modification by osmium it has been suggested that the primary reaction sites do not include bases contained in the intact double helix. Osmium binding to sporadic primary reaction sites (represented e.g. by bases in the vicinity of a single-strand break) in native calf thymus DNA resulted in local changes in DNA conformation limited to a close neighbourhood of the binding site. At higher osmium/nucleotide ratios disordering of the DNA structure over a region extending beyond the immediate binding site was observed. With denatured DNA the same type of structure disordering was detected already in the initial stage of the reaction at osmium/nucleotide ratios as low as 0.01. Osmium binding to the supercoiled Co1E1 DNA resulted in its relaxation without nicking and it increased its sensitivity to linearization by cleavage with nuclease S1. The behaviour of Co1E1 DNA has been explained by the formation of a denatured region in the molecule (accompanied by a coupled loss of duplex and superhelical turns). It has been suggested that osmium can be used to label and to visualize distorted regions in the DNA double helix.

General Physiology and Biophysics

It has been shown earlier that the DNA double helix is opened due to a prolonged contact of the D... more It has been shown earlier that the DNA double helix is opened due to a prolonged contact of the DNA molecule with the surface of the mercury electrode. At neutral pH, the opening process is relatively slow (around 100 s), and it is limited to potentials close to -1.2 V (against SCE). The opening of the double helix has been explained by strains in the DNA molecule due to strong repulsion of the negatively charged phosphate residues from the electrode surface where the polynucleotide chain is anchored via hydrophobic bases. Interaction of the synthetic ds polynucleotides with alternating nucleotide sequences /poly(dA-dT) . poly (dA-dT), poly (dA-dU) . poly (dA-dU), poly (dG-dC) . poly (dG-dC)/ and homopolymer pairs /poly (dA) . poly (dT), poly (rA) . poly (rU) and poly (dG) . poly (dC)/ with the hanging mercury drop electrode has been studied. Changes in reducibility of the polynucleotides were exploited to indicate opening of the double helix. A marked difference in the behaviour was observed between polynucleotides with alternating nucleotide sequence and homopolymer pairs: opening of the double-helical structures of the former polynucleotides occurs at a very narrow potential range (<100mV) (region U), while with the homopolymer pairs containing A . T or A . U pairs, the width of this region is comparable to that of natural DNA (>200 mV). In contrast to natural DNA, the region U of homopolymer pairs is composed of two distinct phases. No region U was observed with poly (dG) . poly (dC). In polynucleotides with alternating nucleotide sequence, the rate of opening of the double helix is strongly dependent on the electrode potential in region U, while in homopolymer pairs, this rate is less potential-dependent. It has been assumed that the difference in the behaviour between homopolymer pairs and polynucleotides with alternating nucleotide sequence is due to differences in adsorbability of the two polynucleotide chains in the molecule of a homopolymer pair (resulting from different adsorbability of purine and pyrimidine bases) in contrast to equal adsorbability of both chains in a polynucleotide molecule with alternating nucleotide sequence. It has been shown that the mercury electrode is a good model of biological surfaces (e.g. membranes), and that the nucleotide sequence-dependent opening (unwinding) of the DNA I HMDE LU RED " Ei Fig. 1. Signals applied and responses obtained (A): in differential pulse polarography (DPP) in connection with the dropping mercury electrode (DME) (representing a technique working with small voltage excursion during the drop life time; (B): in linear sweep voltammetry (LSV) in connection with hanging mercury drop electrode (HMDE). (A): in DPP a single voltage pulse (usually of 10-50 mV) is applied to each drop of mercury dropping from the DME in 1-2 s intervals. The voltage ramp is scanned 1-2 mV/s. (B): in LSV, HMDE is kept for a certain time interval í at the initial potential Ei. During this waiting time t, DNA is adsorbed at the electrode and may undergo certain changes in its secondary structure due to its prolonged interaction with the electrode surface. After the waiting time ;, the electrode potential is rapidly changed (usually 0.5-5 V/s) to more negative values at which ss DNA is reduced (Ered). The height of the voltammetric peak 3 is proportional to the amount of ss DNA reduced at the electrode surface, and it serves as an indication of the extent of surface denaturation of ds DNA. (a, d) thermally denatured DNA (b, c, e, f) ds DNA (in the bulk of solution); (c) at a concentration as usual for measurments of denatured DNA (20-30 ug/ml); (ft) at higher concentra tions (300-400 ug/ml) and a high sensitivity of the instrument; (d, f) Ei in the region T (e.g. -0.6 V); (e) Ei in the region U (e.g. -1.2 V), -for regions U and T see Fig. 2.

General Physiology and Biophysics

Osmium tetroxide, 2,2'-bipyridine (Os,bipy) has been widely applied as a probe of the DNA structu... more Osmium tetroxide, 2,2'-bipyridine (Os,bipy) has been widely applied as a probe of the DNA structure. To obtain information about reactivity of DNA bases toward this probe synthetic homopolynucleotides poly(dT), poly(dC), poly(dG) and poly(dA) were treated with Os,bipy and the content of modified bases mea sured by stripping voltammetry and absorption spectrophotometry. After 20 hours' treatment strong modification of poly(dT) and poly(dC) and weak modification of poly(dG) were observed, while no modification was detected in poly(dA). At short incubation times under conditions close to those usually used in probing the DNA structure the extent of poly(dT) modification was more than 10 times higher than that of poly(dC). Thus, in single-stranded DNA Os,bipy reacts with T >> C and G. Due to the fast reaction of thymines with Os,bipy (and osmium tetroxide, pyri dine) these chemicals can be applied in Maxam-Gilbert nucleotide sequencing as agents specific for thymines in single-stranded DNA.

General Physiology and Biophysics

Synthetic homopolyribonucleotides poly(A), poly(U), poly(C), and poly(G), poly(A, G, U), apurinic... more Synthetic homopolyribonucleotides poly(A), poly(U), poly(C), and poly(G), poly(A, G, U), apurinic acid and native and denatured DNA from calf thymus were analyzed by means of cyclic voltammetry (CV) using a hanging mercury drop electrode. It was shown that guanine containing polynucleotides, i.e. poly(G), poly(A, G, U) and DNA yield an anodic peak of guanine in the vicinity of a potential of -0.3 V (against a saturated calomel electrode). The guanine peak appeared only at a sufficiently negative switching potential (about -2 V). The appearance of the guanine peak was conditioned by a reduction of guanine residues in the region of the switching potential and reoxidation of the reduction product in the vicinity of -0.3 V. Native and thermally denatured DNAs were investigated under the conditions of both complete and incomplete coverage of the electrode in various background electrolytes. Both DNA forms yielded anodic CV peaks of guanine with the peak of denatured DNA being always higher than that of native DNA. Irradiation of native DNA with relatively small doses of gamma radiation (5-120 Gy) resulted in an increase of the anodic peak. A comparison of changes induced by gamma radiation in the anodic (guanine) and cathodic (reduction of adenine and cytosine) peaks showed a steeper increase of the cathodic peak as compared to that of the anodic one. It has been concluded that in the given dose range the DNA double-helical structure is mainly damaged in the adenine-thymine rich regions.

Electrochemically active labels have been applied in electrochemical nucleic acid analysis and DN... more Electrochemically active labels have been applied in electrochemical nucleic acid analysis and DNA biosensors (reviewed in 1,2). Electroactive species (covalently coupled to DNA or binding the DNA non-covalently) are employed to improve sensitivity and/or specificity of DNA detection. This may be reached via choosing markers providing reversible and/or catalytic high electron yield signals, occurring at less extreme potentials than irreversible intrinsic DNA reduction (at mercury or solid amalgam electrodes) or oxidation (usually at carbon electrodes) electrochemical responses 1,2 . Osmium tetroxide complexes (Os,L) were for the first time introduced as electroactive DNA markers and chemical probes of DNA structure in the early 1980's (3 and refs. therein). Complexes of OsO 4 with nitrogen ligands such 2,2'-bipyridine (bipy) covalently bind to the 5,6 double bond of the pyrimidine ring (thymine is about 10-fold more reactive than cytosine); purine bases practically do not re...

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1977

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and... more Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribocytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylic acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible --S--S--groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdi6ka's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdi~ka's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can, however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.

Weimar (D.D.lZ.). o3o2-4958 / o/o317-o332 © Elsevier Sequoia S.A.

Sensors (Basel, Switzerland), 2015

Interest in electrochemical analysis of purine nucleobases and few other important purine derivat... more Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications.

Electrochemical DNA Biosensors, 2012

2010 IEEE Sensors, 2010

An innovative electrochemical sensor based on a combination of the elimination voltammetry and ad... more An innovative electrochemical sensor based on a combination of the elimination voltammetry and adsorptive stripping (AdS) techniques with a slightly soluble complex is presented. The test of our approach was aimed at analysis of aminopurines and oxopurines on carbon paste (CPE) and pencil graphite electrodes (PeGE). The voltammetric signals of purine derivatives are amplified: (i) by increasing the surface concentration

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

The electrochemical behaviour of 30 purine and pyrimidine derivatives and of a further 12 derivat... more The electrochemical behaviour of 30 purine and pyrimidine derivatives and of a further 12 derivatives containing sulphur or halogens was studied. It was demonstrated that most of these substances react with the electrode mercury and form sparingly soluble compounds; this phenomenon can be exploited for the determination of purine and pyrimidine derivatives at low concentrations. The relation between the structural formulae of the substances and their ability to yield anodic polarographic currents conditioned by formation of sparingly soluble compounds with mercury was found. The behaviour of adenine and 8-oxyadenine was studied in greater detail by means of differential (DPP) and normal pulse polarography (NPP), d.c. polarography and cathodic stripping voltammetry (CSV). Both substances can be determined with the aid of CSV at concentrations of the order of magnitude of 10 -9 M, while DPP may be used at concentrations three to four orders of magnitude higher. Interactions of some purine and pyrimidine derivatives with Hg(II) ions in homogeneous aqueous solutions were investigated. On the one hand, a correlation was found between the ability of these substances to react with mercury in solution and form precipitates, and, on the other hand, to yield anodic polarographic currents.

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

... 128 (1981)Elsevier Sequoia SA, Lausanne --- Printed in The Netherlands497444 -- ELECTROCHEMIC... more ... 128 (1981)Elsevier Sequoia SA, Lausanne --- Printed in The Netherlands497444 -- ELECTROCHEMICAL ANALYSIS OF POLYNUCLEOTIDES *EMIL PALE~EK, EMILIE ... It does not react, however, withbases incorporated in an intact Watson--Crick DNA double helix; this agent ...

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1981

Closed duplex (cd) and open circular (oc) forms of DNA of the plasmid Col E1 were studied by mean... more Closed duplex (cd) and open circular (oc) forms of DNA of the plasmid Col E1 were studied by means of a.c. and differential pulse polarography (d.p.p.).