The previously reported approach of orthogonal multipotential redox coding of all four DNA bases allowed only analysis of the relative nucleotide composition of short DNA stretches. Here, we present two methods for normalization of the electrochemical readout to facilitate the determination of the total nucleotide composition. The first method is based on the presence or absence of an internal standard of 7-deaza-2'-deoxyguanosine in a DNA primer. The exact composition of the DNA was elucidated upon two parallel analyses and the subtraction of the electrochemical signal intensities. The second approach took advantage of a 5'-viologen modified primer, with this fifth orthogonal redox label acting as a reference for signal normalization, thus allowing accurate electrochemical sequence analysis in a single read. Both approaches were tested using various sequences, and the voltammetric signals obtained were normalized using either the internal standard or the reference label and demonstrated to be in perfect agreement with the actual nucleotide composition, highlighting the potential for targeted DNA sequence analysis.

• MeSH
• DNA primery MeSH
• DNA * chemie   MeSH
• nukleotidy * chemie   MeSH
• oxidace-redukce MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA primery MeSH
• DNA * MeSH
• nukleotidy * MeSH

Osteoporosis is a multifactorial disease influenced by genetic and environmental factors, which contributes to an increased risk of bone fracture, but early diagnosis of this disease cannot be achieved using current techniques. We describe a generic platform for the targeted electrochemical genotyping of SNPs identified by genome-wide association studies to be associated with a genetic predisposition to osteoporosis. The platform exploits isothermal solid-phase primer elongation with ferrocene-labeled nucleoside triphosphates. Thiolated reverse primers designed for each SNP were immobilized on individual gold electrodes of an array. These primers are designed to hybridize to the SNP site at their 3'OH terminal, and primer elongation occurs only where there is 100% complementarity, facilitating the identification and heterozygosity of each SNP under interrogation. The platform was applied to real blood samples, which were thermally lysed and directly used without the need for DNA extraction or purification. The results were validated using Taqman SNP genotyping assays and Sanger sequencing. The assay is complete in just 15 min with a total cost of 0.3€ per electrode. The platform is completely generic and has immense potential for deployment at the point of need in an automated device for targeted SNP genotyping with the only required end-user intervention being sample addition.

• Publikační typ
• časopisecké články MeSH

Here, we report the electrochemical detection of single-point mutations using solid-phase isothermal primer elongation with redox-labeled oligonucleotides. A single-base mutation associated with resistance to rifampicin, an antibiotic commonly used for the treatment of Mycobacterium tuberculosis, was used as a model system to demonstrate a proof-of-concept of the approach. Four 5'-thiolated primers, designed to be complementary with the same fragment of the target sequence and differing only in the last base, addressing the polymorphic site, were self-assembled via chemisorption on individual gold electrodes of an array. Following hybridization with single-stranded DNA, Klenow (exo-) DNA polymerase-mediated primer extension with ferrocene-labeled 2'-deoxyribonucleoside triphosphates (dNFcTPs) was only observed to proceed at the electrode where there was full complementarity between the surface-tethered probe and the target DNA being interrogated. We tested all four ferrocenylethynyl-linked dNTPs and optimized the ratio of labeled/natural nucleotides to achieve maximum sensitivity. Following a 20 min hybridization step, Klenow (exo-) DNA polymerase-mediated primer elongation at 37 °C for 5 min was optimal for the enzymatic incorporation of a ferrocene-labeled nucleotide, achieving unequivocal electrochemical detection of a single-point mutation in 14 samples of genomic DNA extracted from Mycobacterium tuberculosis strains. The approach is rapid, cost-effective, facile, and can be extended to multiplexed electrochemical single-point mutation genotyping.

• Klíčová slova
• Klenow (exo-) DNA polymerase, ferrocene-labeled nucleotides, nucleoside triphosphates, single-nucleotide polymorphism (SNP), single-point mutation, solid-phase primer elongation,
• MeSH
• jednonukleotidový polymorfismus MeSH
• metaloceny MeSH
• Mycobacterium tuberculosis * genetika   MeSH
• oxidace-redukce MeSH
• rifampin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• metaloceny MeSH
• rifampin MeSH

A 153-mer target DNA was amplified using ethynyl ferrocene dATP and a tailed forward primer resulting in a duplex with a single-stranded DNA tail for hybridization to a surface-tethered probe. A thiolated probe containing the sequence complementary to the tail as well as a 15 polythimine vertical spacer with a (CH2)6 spacer was immobilized on the surface of a gold electrode and hybridized to the ferrocene-modified complementary strand. Potential step chronoamperometry and cyclic voltammetry were used to probe the potential of zero charge, PZC, and the rate of heterogeneous electron transfer between the electrode and the immobilized ferrocene moieties. Chronoamperometry gives three, well-resolved exponential current-time decays corresponding to ferrocene centers located within 13 Å (4 bases) along the duplex. Significantly, the apparent standard heterogeneous electron transfer rate constant, kappo, observed depends on the initial potential, i.e., the rate of electron transfer at zero driving force is not the same for oxidation and reduction of the ferrocene labels. Moreover, the presence of ions, such as Sr2+, that strongly ion pair with the negatively charged DNA backbone modulates the electron transfer rate significantly. Specifically, kappo = 246 ± 23.5 and 14 ± 1.2 s-1 for reduction and oxidation, respectively, where the Sr2+ concentration is 10 mM, but the corresponding values in 1 M Sr2+ are 8 ± 0.8 and 150 ± 12 s-1. While other factors may be involved, these results are consistent with a model in which a low Sr2+ concentration and an initial potential that is negative of the PZC lead to electrostatic repulsion of the negatively charged DNA backbone and the negatively charged electrode. This leads to the DNA adopting an extended configuration (concertina open), resulting in a slow rate of heterogeneous electron transfer. In contrast, for ferrocene reduction, the initial potential is positive of PZC and the negatively charged DNA is electrostatically attracted to the electrode (concertina closed), giving a shorter electron transfer distance and a higher rate of heterogeneous electron transfer. When the Sr2+ concentration is high, the charge on the DNA backbone is compensated by the electrolyte and the charge on the electrode dominates the electron transfer dynamics and the opposite potential dependence is observed. These results open up the possibility of electromechanical switching using DNA superstructures.

• MeSH
• DNA * genetika   MeSH
• elektrody MeSH
• elektrony * MeSH
• metaloceny MeSH
• statická elektřina MeSH
• transport elektronů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA * MeSH
• metaloceny MeSH

Three sets of 7-deazaadenine and cytosine nucleosides and nucleoside triphosphates bearing either unsubstituted ferrocene, octamethylferrocene and ferrocenecarboxamide linked through an alkyne tether to position 7 or 5, respectively, were designed and synthesized. The modified dNFcX TPs were good substrates for KOD XL DNA polymerase in primer extension and were used for enzymatic synthesis of redox-labelled DNA probes. Square-wave voltammetry showed that the octamethylferrocene oxidation potential was shifted to lower values, whilst the ferrocenecarboxamide was shifted to higher potentials, as compared to ferrocene. Tailed PEX products containing different ratios of Fc-labelled A (dAFc ) and FcPa-labelled C (dCFcPa ) were synthesized and hybridized with capture oligonucleotides immobilized on gold electrodes to study the electrochemistry of the redox-labelled DNA. Clearly distinguishable, fully orthogonal and ratiometric peaks were observed for the dAFc and dCFcPa bases in DNA, demonstrating their potential for use in redox coding of nucleobases and for the direct electrochemical measurement of the relative ratio of nucleobases in an unknown sequence of DNA.

• Klíčová slova
• DNA, electrochemistry, ferrocenes, nucleobases, redox labelling,
• MeSH
• barvení a značení metody   MeSH
• cytidintrifosfát chemie   MeSH
• DNA sondy chemická syntéza   chemie   MeSH
• DNA-dependentní DNA-polymerasy metabolismus   MeSH
• DNA chemie   metabolismus   MeSH
• elektrochemické techniky MeSH
• metaloceny chemie   MeSH
• nukleotidy chemie   MeSH
• oxidace-redukce MeSH
• substrátová specifita MeSH
• železnaté sloučeniny chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytidintrifosfát MeSH
• DNA sondy MeSH
• DNA-dependentní DNA-polymerasy MeSH
• DNA MeSH
• ferrocene MeSH Prohlížeč
• metaloceny MeSH
• nukleotidy MeSH
• železnaté sloučeniny MeSH

We report the duplex amplification of two plasmid DNA markers involved in the virulence of Bacillus anthracis, CAP and PAG, and the direct electrochemical detection of these amplicons. The method consists of the simultaneous amplification of the two targets in a single-pot reaction via polymerase chain reaction (PCR) using tailed primers and ferrocene-labeled dATP. Following amplification, the PCR products hybridize to probes immobilized on electrodes in a microfabricated electrode array chip. The incorporated ferrocene labeled dATP is then detected using square wave voltammetry. We evaluated the effect of electrolyte cations, anions, and concentration to condense, bend, and shrink double-stranded DNA and their effect on the intensity of the ferrocene signal. We obtained detection limits of 0.8 and 3.4 fM for CAP and PAG targets, respectively. We successfully developed a method to detect the presence of both targets in genomic DNA extracted from real samples.

• Publikační typ
• časopisecké články MeSH

A series of 2-alkylamino-2'-deoxyadenosine triphosphates (dATP) was prepared and found to be substrates for the Therminator DNA polymerase, which incorporated only one modified nucleotide into the primer. Using a template encoding for two consecutive adenines, conditions were found for incorporation of either one or two modified nucleotides. In all cases, addition of a mixture of natural dNTPs led to primer extension resulting in site-specific single modification of DNA in the minor groove. The allylamino-substituted DNA was used for the thiol-ene addition, whereas the propargylamino-DNA for the CuAAC click reaction was used to label the DNA with a fluorescent dye in the minor groove. The approach was used to construct FRET probes for detection of oligonucleotides.

• Klíčová slova
• DNA, fluorescent probes, nucleotides, oligonucleotides, polymerases,
• MeSH
• alylové sloučeniny chemie   MeSH
• deoxyadeninnukleotidy chemie   MeSH
• DNA chemie   MeSH
• fluorescenční barviva chemie   MeSH
• konformace nukleové kyseliny MeSH
• oligonukleotidy analýza   MeSH
• pargylin analogy a deriváty   chemie   MeSH
• propylaminy chemie   MeSH
• rezonanční přenos fluorescenční energie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 2'-deoxyadenosine triphosphate MeSH Prohlížeč
• alylové sloučeniny MeSH
• deoxyadeninnukleotidy MeSH
• DNA MeSH
• fluorescenční barviva MeSH
• oligonukleotidy MeSH
• pargylin MeSH
• propargylamine MeSH Prohlížeč
• propylaminy MeSH

2'-Deoxyadenosine triphosphate (dATP) derivatives bearing diverse substituents (Cl, NH2 , CH3 , vinyl, ethynyl, and phenyl) at position 2 were prepared and tested as substrates for DNA polymerases. The 2-phenyl-dATP was not a substrate for DNA polymerases, but the dATPs bearing smaller substituents were good substrates in primer-extension experiments, producing DNA substituted in the minor groove. The vinyl-modified DNA was applied in thiol-ene addition and the ethynyl-modified DNA was applied in a CuAAC click reaction to form DNA labelled with fluorescent dyes in the minor groove.

• Klíčová slova
• DNA modification, DNA polymerase, bioconjugation, fluorescent labelling, nucleotides,
• MeSH
• denaturace nukleových kyselin MeSH
• deoxyadeninnukleotidy chemie   metabolismus   MeSH
• DNA-dependentní DNA-polymerasy metabolismus   MeSH
• DNA chemie   metabolismus   MeSH
• konformace nukleové kyseliny MeSH
• sekvence nukleotidů MeSH
• substrátová specifita MeSH
• termodynamika MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2'-deoxyadenosine triphosphate MeSH Prohlížeč
• deoxyadeninnukleotidy MeSH
• DNA-dependentní DNA-polymerasy MeSH
• DNA MeSH

New redox labelling of DNA by an azido group which can be chemically transformed to nitrophenyltriazole or silenced to phenyltriazole was developed and applied to the electrochemical detection of DNA-protein interactions. 5-(4-Azidophenyl)-2'-deoxycytidine and 7-(4-azidophenyl)-7-deaza-2'-deoxyadenosine nucleosides were prepared by aqueous-phase Suzuki cross-coupling and converted to nucleoside triphosphates (dNTPs) which served as substrates for incorporation into DNA by DNA polymerase. The azidophenyl-modified nucleotides and azidophenyl-modified DNA gave a strong signal in voltammetric studies, at -0.9 V, due to reduction of the azido function. The Cu-catalyzed click reaction of azidophenyl-modified nucleosides or azidophenyl-modified DNA with 4-nitrophenylacetylene gave nitrophenyl-substituted triazoles, exerting a reduction peak at -0.4 V under voltammetry, whereas the click reaction with phenylacetylene gave electrochemically silent phenyltriazoles. The transformation of the azidophenyl label to nitrophenyltriazole was used for electrochemical detection of DNA-protein interactions (p53 protein) since only those azidophenyl groups in the parts of the DNA not shielded by the bound p53 protein were transformed to nitrophenyltriazoles, whereas those covered by the protein were not.

• Publikační typ
• časopisecké články MeSH

A set of 6 base-modified 2'-deoxyadenosine derivatives was incorporated to diverse DNA sequences by primer extension using Vent (exo-) polymerase and the influence of the modification on cleavage by diverse restriction endonucleases was studied. While 8-substituted (Br or methyl) adenine derivatives were well tolerated by the restriction enzymes and the corresponding sequences were cleaved, the presence of 7-substituted 7-deazaadenine in the recognition sequence resulted in blocking of cleavage by some enzymes depending on the nature and size of the 7-substituent. All sequences with modifications outside of the recognition sequence were perfectly cleaved by all the restriction enzymes. The results are useful both for protection of some sequences from cleavage and for manipulation of functionalized DNA by restriction cleavage.

• MeSH
• deoxyadeninnukleotidy chemie   MeSH
• deoxyadenosiny chemie   MeSH
• DNA-dependentní DNA-polymerasy metabolismus   MeSH
• DNA chemie   MeSH
• elektroforéza v polyakrylamidovém gelu MeSH
• restrikční endonukleasy typu II metabolismus   MeSH
• štěpení DNA * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2'-deoxyadenosine MeSH Prohlížeč
• deoxyadeninnukleotidy MeSH
• deoxyadenosiny MeSH
• DNA-dependentní DNA-polymerasy MeSH
• DNA MeSH
• restrikční endonukleasy typu II MeSH
• Tli polymerase MeSH Prohlížeč