1
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Mir B, Serrano-Chacón I, Medina P, Macaluso V, Terrazas M, Gandioso A, Garavís M, Orozco M, Escaja N, González C. Site-specific incorporation of a fluorescent nucleobase analog enhances i-motif stability and allows monitoring of i-motif folding inside cells. Nucleic Acids Res 2024; 52:3375-3389. [PMID: 38366792 PMCID: PMC11014255 DOI: 10.1093/nar/gkae106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 01/17/2024] [Accepted: 02/09/2024] [Indexed: 02/18/2024] Open
Abstract
The i-motif is an intriguing non-canonical DNA structure, whose role in the cell is still controversial. Development of methods to study i-motif formation under physiological conditions in living cells is necessary to study its potential biological functions. The cytosine analog 1,3-diaza-2-oxophenoxazine (tCO) is a fluorescent nucleobase able to form either hemiprotonated base pairs with cytosine residues, or neutral base pairs with guanines. We show here that when tCO is incorporated in the proximity of a G:C:G:C minor groove tetrad, it induces a strong thermal and pH stabilization, resulting in i-motifs with Tm of 39ºC at neutral pH. The structural determination by NMR methods reveals that the enhanced stability is due to a large stacking interaction between the guanines of the tetrad with the tCO nucleobase, which forms a tCO:C+ in the folded structure at unusually-high pHs, leading to an increased quenching in its fluorescence at neutral conditions. This quenching is much lower when tCO is base-paired to guanines and totally disappears when the oligonucleotide is unfolded. By taking profit of this property, we have been able to monitor i-motif folding in cells.
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Affiliation(s)
- Bartomeu Mir
- Instituto de Química Física ‘Blas Cabrera’. CSIC. Serrano 119. 28006 Madrid. Spain
- Inorganic and Organic Chemistry Department. Organic Chemistry Section and IBUB. University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona. Spain
| | - Israel Serrano-Chacón
- Instituto de Química Física ‘Blas Cabrera’. CSIC. Serrano 119. 28006 Madrid. Spain
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
| | - Pedro Medina
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
- Departament de Bioquímica i Biomedicina. Facultat de Biologia. Universitat de Barcelona. 08028 Barcelona. Spain
| | - Veronica Macaluso
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
| | - Montserrat Terrazas
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
- Inorganic and Organic Chemistry Department. Organic Chemistry Section and IBUB. University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona. Spain
| | - Albert Gandioso
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
| | - Miguel Garavís
- Instituto de Química Física ‘Blas Cabrera’. CSIC. Serrano 119. 28006 Madrid. Spain
| | - Modesto Orozco
- Institute for Research in Biomedicine (IRB Barcelona). The Barcelona Institute of Science and Technology (BIST). 08028 Barcelona. Spain
- Departament de Bioquímica i Biomedicina. Facultat de Biologia. Universitat de Barcelona. 08028 Barcelona. Spain
| | - Núria Escaja
- Inorganic and Organic Chemistry Department. Organic Chemistry Section and IBUB. University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona. Spain
| | - Carlos González
- Instituto de Química Física ‘Blas Cabrera’. CSIC. Serrano 119. 28006 Madrid. Spain
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2
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Sundar Rajan V, Wypijewska Del Nogal A, Levin S, Wilhelmsson LM, Westerlund F. Exploring the conformational dynamics of the SARS-CoV-2 SL4 hairpin by combining optical tweezers and base analogues. NANOSCALE 2024; 16:752-764. [PMID: 38087988 PMCID: PMC10763987 DOI: 10.1039/d3nr04110g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 12/06/2023] [Indexed: 01/04/2024]
Abstract
The parasitic nature of the SARS-CoV-2 virus demands selective packaging of its RNA genome (gRNA) from the abundance of other nucleic acids present in infected cells. Despite increasing evidence that stem-loop 4 (SL4) of the gRNA 5' UTR is involved in the initiation of this process by binding the nucleocapsid (N) protein, little is known about its conformational dynamics. Here, we unravel the stability, dynamics and (un)folding pathways of SL4 using optical tweezers and a base analogue, tCO, that provides a local and subtle increase in base stacking without perturbing hydrogen bonding. We find that SL4 (un)folds mainly in a single step or through an intermediate, encompassing nucleotides from the central U bulge to the hairpin loop. Due to an upper-stem CU mismatch, SL4 is prone to misfold, the extent of which can be tuned by incorporating tCO at different positions. Our study contributes to a better understanding of SARS-CoV-2 packaging and the design of drugs targeting SL4. We also highlight the generalizability of using base analogues in optical tweezers experiments for probing intramolecular states and conformational transitions of various nucleic acids at the level of single molecules and with base-pair resolution.
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Affiliation(s)
- Vinoth Sundar Rajan
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
- Division of Chemistry and Biochemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - Anna Wypijewska Del Nogal
- Division of Chemistry and Biochemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - Sune Levin
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - L Marcus Wilhelmsson
- Division of Chemistry and Biochemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - Fredrik Westerlund
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
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3
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Wang D, Shalamberidze A, Arguello AE, Purse BW, Kleiner RE. Live-Cell RNA Imaging with Metabolically Incorporated Fluorescent Nucleosides. J Am Chem Soc 2022; 144:14647-14656. [PMID: 35930766 PMCID: PMC9940818 DOI: 10.1021/jacs.2c04142] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fluorescence imaging is a powerful method for probing macromolecular dynamics in biological systems; however, approaches for cellular RNA imaging are limited to the investigation of individual RNA constructs or bulk RNA labeling methods compatible primarily with fixed samples. Here, we develop a platform for fluorescence imaging of bulk RNA dynamics in living cells. We show that fluorescent bicyclic and tricyclic cytidine analogues can be metabolically incorporated into cellular RNA by overexpression of uridine-cytidine kinase 2. In particular, metabolic feeding with the tricyclic cytidine-derived nucleoside tC combined with confocal imaging enables the investigation of RNA synthesis, degradation, and trafficking at single-cell resolution. We apply our imaging modality to study RNA metabolism and localization during the oxidative stress response and find that bulk RNA turnover is greatly accelerated upon NaAsO2 treatment. Furthermore, we identify cytoplasmic RNA granules containing RNA transcripts generated during oxidative stress that are distinct from canonical stress granules and P-bodies and co-localize with the RNA helicase DDX6. Taken together, our work provides a powerful approach for live-cell RNA imaging and reveals how cells reshape RNA transcriptome dynamics in response to oxidative stress.
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Affiliation(s)
- Danyang Wang
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Ana Shalamberidze
- Department of Chemistry and Biochemistry and the Viral Information Institute, San Diego State University, San Diego, CA 92182, USA
| | | | - Byron W. Purse
- Department of Chemistry and Biochemistry and the Viral Information Institute, San Diego State University, San Diego, CA 92182, USA
| | - Ralph E. Kleiner
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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4
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Thienoguanosine, a unique non-perturbing reporter for investigating rotational dynamics of DNA duplexes and their complexes with proteins. Int J Biol Macromol 2022; 213:210-225. [DOI: 10.1016/j.ijbiomac.2022.05.162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/02/2022] [Accepted: 05/23/2022] [Indexed: 11/05/2022]
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5
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Lanphere C, Ciccone J, Dorey A, Hagleitner-Ertuğrul N, Knyazev D, Haider S, Howorka S. Triggered Assembly of a DNA-Based Membrane Channel. J Am Chem Soc 2022; 144:4333-4344. [PMID: 35253434 PMCID: PMC8931747 DOI: 10.1021/jacs.1c06598] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Indexed: 01/01/2023]
Abstract
Chemistry is in a powerful position to synthetically replicate biomolecular structures. Adding functional complexity is key to increase the biomimetics' value for science and technology yet is difficult to achieve with poorly controlled building materials. Here, we use defined DNA blocks to rationally design a triggerable synthetic nanopore that integrates multiple functions of biological membrane proteins. Soluble triggers bind via molecular recognition to the nanopore components changing their structure and membrane position, which controls the assembly into a defined channel for efficient transmembrane cargo transport. Using ensemble, single-molecule, and simulation analysis, our activatable pore provides insight into the kinetics and structural dynamics of DNA assembly at the membrane interface. The triggered channel advances functional DNA nanotechnology and synthetic biology and will guide the design of controlled nanodevices for sensing, cell biological research, and drug delivery.
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Affiliation(s)
- Conor Lanphere
- Department
of Chemistry, Institute of Structural Molecular Biology, University College London, London WC1H 0AJ, United Kingdom
| | - Jonah Ciccone
- Department
of Chemistry, Institute of Structural Molecular Biology, University College London, London WC1H 0AJ, United Kingdom
| | - Adam Dorey
- Department
of Chemistry, Institute of Structural Molecular Biology, University College London, London WC1H 0AJ, United Kingdom
| | | | - Denis Knyazev
- Institute
of Applied Experimental Biophysics, Johannes
Kepler University, 4040 Linz, Austria
| | - Shozeb Haider
- Department
of Pharmaceutical and Biological Chemistry, University College London School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Stefan Howorka
- Department
of Chemistry, Institute of Structural Molecular Biology, University College London, London WC1H 0AJ, United Kingdom
- Institute
of Applied Experimental Biophysics, Johannes
Kepler University, 4040 Linz, Austria
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6
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He X, Kuang S, Gao Q, Xie Y, Ming X. Bright fluorescent purine analogues as promising probes. NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS 2021; 41:45-60. [PMID: 34806926 DOI: 10.1080/15257770.2021.2004418] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/06/2021] [Accepted: 11/06/2021] [Indexed: 10/19/2022]
Abstract
Modified bright fluorescent nucleosides that respond to the microenvironment have great potential as probes. A series of novel 8-(phenylethynyl)phenylated 2-amino-2'-deoxyadenosine and 2'-deoxyisoguanosine derivatives have been synthesized by Sonogashira-type coupling reaction and Suzuki reaction. The maximum emission of the new compounds is in the visible region, with strong solvatochromicity and pH-dependent fluorescent properties. Furthermore, some of them exhibit bright fluorescence emissions in various solvents (ε × Φ = 4000-39,000 cm-1 M-1). These consequences indicate that purine analogues could respond to the microenvironment and serve as promising fluorescent probes.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.2004418 .
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Affiliation(s)
- Xin He
- School of Pharmacy, Chengdu Medical College, Chengdu, Sichuan, China
| | - Shuang Kuang
- School of Pharmacy, Chengdu Medical College, Chengdu, Sichuan, China
| | - Qian Gao
- School of Pharmacy, Chengdu Medical College, Chengdu, Sichuan, China
| | - YuXin Xie
- School of Pharmacy, Chengdu Medical College, Chengdu, Sichuan, China
| | - Xin Ming
- School of Pharmacy, Chengdu Medical College, Chengdu, Sichuan, China
- Study on the Structure-Specific Small Molecular Drug in Sichuan Province College Key Laboratory, Chengdu Medical College, Chengdu, Sichuan, China
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7
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Pre-concentration of microRNAs by LNA-modified magnetic beads for enhancement of electrochemical detection. Sci Rep 2021; 11:19650. [PMID: 34608225 PMCID: PMC8490432 DOI: 10.1038/s41598-021-99145-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 09/21/2021] [Indexed: 12/29/2022] Open
Abstract
MicroRNAs are extremely promising candidates for early cancer diagnosis and prognosis. The levels of circulating microRNAs provide valuable information about cancer disease at its early stages. However, the levels of microRNAs that need to be detected are extremely low and difficult to discriminate from a large pool of oligonucleotides. There is the need for accurate, rapid and sensitive detection methodologies for detection of microRNAs. We developed electrochemical impedance spectroscopy peptide nucleic acid (PNA)-based sensors that can detect miRNAs in diluted serum with a limit of detection of 0.38 fM. In order to further improve the accuracy and reliability of the sensors, we developed an assay using magnetic beads for simple and rapid fishing of target microRNAs from solution and its pre-concentration prior to electrochemical detection. Our methodology utilizes magnetic beads for the capture of the target microRNA from solution and brings the concentrated sample to the sensor surface. We modify the magnetic beads with locked nucleic acids (LNA), which have high affinity and specificity to their complementary microRNA sequence. The separated and concentrated microRNA is then detected using the PNA-based sensors. By exposing the sensing electrodes only to the captured microRNAs, interferences from other nucleotides or biomolecules from the sample are eliminated.
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8
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Sundar Rajan V, Viader-Godoy X, Lin YL, Dutta U, Ritort F, Westerlund F, Wilhelmsson LM. Mechanical characterization of base analogue modified nucleic acids by force spectroscopy. Phys Chem Chem Phys 2021; 23:14151-14155. [PMID: 34180930 PMCID: PMC8261857 DOI: 10.1039/d1cp01985f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We use mechanical unfolding of single DNA hairpins with modified bases to accurately assess intra- and intermolecular forces in nucleic acids. As expected, the modification stabilizes the hybridized hairpin, but we also observe intriguing stacking interactions in the unfolded hairpin. Our study highlights the benefit of using base-modified nucleic acids in force-spectroscopy.
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Affiliation(s)
- Vinoth Sundar Rajan
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden. and Department of Biology and Biological Engineering, Chalmers University of Technology, Sweden.
| | - Xavier Viader-Godoy
- Small Biosystems Lab, Condensed Matter Physics Department, Universitat de Barcelona, C/Marti i Franques 1, Barcelona 08028, Spain
| | - Yii-Lih Lin
- Department of Biology and Biological Engineering, Chalmers University of Technology, Sweden.
| | - Uttama Dutta
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden. and Department of Biology and Biological Engineering, Chalmers University of Technology, Sweden.
| | - Felix Ritort
- Small Biosystems Lab, Condensed Matter Physics Department, Universitat de Barcelona, C/Marti i Franques 1, Barcelona 08028, Spain
| | - Fredrik Westerlund
- Department of Biology and Biological Engineering, Chalmers University of Technology, Sweden.
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden.
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9
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Nilsson JR, Baladi T, Gallud A, Baždarević D, Lemurell M, Esbjörner EK, Wilhelmsson LM, Dahlén A. Fluorescent base analogues in gapmers enable stealth labeling of antisense oligonucleotide therapeutics. Sci Rep 2021; 11:11365. [PMID: 34059711 PMCID: PMC8166847 DOI: 10.1038/s41598-021-90629-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/13/2021] [Indexed: 01/28/2023] Open
Abstract
To expand the antisense oligonucleotide (ASO) fluorescence labeling toolbox beyond covalent conjugation of external dyes (e.g. ATTO-, Alexa Fluor-, or cyanine dyes), we herein explore fluorescent base analogues (FBAs) as a novel approach to endow fluorescent properties to ASOs. Both cytosine and adenine analogues (tC, tCO, 2CNqA, and pA) were incorporated into a 16mer ASO sequence with a 3-10-3 cEt-DNA-cEt (cEt = constrained ethyl) gapmer design. In addition to a comprehensive photophysical characterization, we assess the label-induced effects on the gapmers' RNA affinities, RNA-hybridized secondary structures, and knockdown efficiencies. Importantly, we find practically no perturbing effects for gapmers with single FBA incorporations in the biologically critical gap region and, except for pA, the FBAs do not affect the knockdown efficiencies. Incorporating two cytosine FBAs in the gap is equally well tolerated, while two adenine analogues give rise to slightly reduced knockdown efficiencies and what could be perturbed secondary structures. We furthermore show that the FBAs can be used to visualize gapmers inside live cells using fluorescence microscopy and flow cytometry, enabling comparative assessment of their uptake. This altogether shows that FBAs are functional ASO probes that provide a minimally perturbing in-sequence labeling option for this highly relevant drug modality.
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Affiliation(s)
- Jesper R Nilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Tom Baladi
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden.,Medicinal Chemistry, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden.,Oligonucleotide Discovery, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Audrey Gallud
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden.,Advanced Drug Delivery, Pharmaceutical Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Dženita Baždarević
- Bioscience, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Malin Lemurell
- Medicinal Chemistry, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Elin K Esbjörner
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Anders Dahlén
- Oligonucleotide Discovery, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden.
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10
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Füchtbauer AF, Wranne MS, Sarangamath S, Bood M, El-Sagheer AH, Brown T, Gradén H, Grøtli M, Wilhelmsson LM. Lighting Up DNA with the Environment-Sensitive Bright Adenine Analogue qAN4. Chempluschem 2021; 85:319-326. [PMID: 32045137 DOI: 10.1002/cplu.201900712] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/24/2020] [Indexed: 12/20/2022]
Abstract
The fluorescent adenine analogue qAN4 was recently shown to possess promising photophysical properties, including a high brightness as a monomer. Here we report the synthesis of the phosphoramidite of qAN4 and its successful incorporation into DNA oligonucleotides using standard solid-phase synthesis. Circular dichroism and thermal melting studies indicate that the qAN4-modification has a stabilizing effect on the B-form of DNA. Moreover, qAN4 base-pairs selectively with thymine with mismatch penalties similar to those of mismatches of adenine. The low energy absorption band of qAN4 inside DNA has its peak around 358 nm and the emission in duplex DNA is partly quenched and blue-shifted (ca. 410 nm), compared to the monomeric form. The spectral properties of the fluorophore also show sensitivity to pH; a property that may find biological applications. Quantum yields in single-stranded DNA range from 1-29 % and in duplex DNA from 1-7 %. In combination with the absorptive properties, this gives an average brightness inside duplex DNA of 275 M-1 cm-1 , more than five times higher than the most used environment-sensitive fluorescent base analogue, 2-aminopurine. Finally, we show that qAN4 can be used to advantage as a donor for interbase FRET applications in combination with adenine analogue qAnitro as an acceptor.
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Affiliation(s)
- Anders F Füchtbauer
- Department of Chemistry and Chemical Engineering Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Moa S Wranne
- Department of Chemistry and Chemical Engineering Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Sangamesh Sarangamath
- Department of Chemistry and Chemical Engineering Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Mattias Bood
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96, Gothenburg, Sweden.,Cardiovascular Renal and Metabolic Diseases IMED Biotech Unit, AstraZeneca Gothenburg, Pepparedsleden 1, SE-431 83, Mölndal, Sweden
| | - Afaf H El-Sagheer
- Department of Chemistry, University of Oxford Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.,Chemistry Branch Department of Science and Mathematics Faculty of Petroleum and Mining Engineering, Suez University, Suez, 43721, Egypt
| | - Tom Brown
- Department of Chemistry, University of Oxford Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Henrik Gradén
- Cardiovascular Renal and Metabolic Diseases IMED Biotech Unit, AstraZeneca Gothenburg, Pepparedsleden 1, SE-431 83, Mölndal, Sweden
| | - Morten Grøtli
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96, Gothenburg, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
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11
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Kishimoto Y, Nakagawa O, Fujii A, Yoshioka K, Nagata T, Yokota T, Hari Y, Obika S. 2',4'-BNA/LNA with 9-(2-Aminoethoxy)-1,3-diaza-2-oxophenoxazine Efficiently Forms Duplexes and Has Enhanced Enzymatic Resistance*. Chemistry 2021; 27:2427-2438. [PMID: 33280173 PMCID: PMC7898338 DOI: 10.1002/chem.202003982] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Indexed: 11/28/2022]
Abstract
Artificial nucleic acids are widely used in various technologies, such as nucleic acid therapeutics and DNA nanotechnologies requiring excellent duplex-forming abilities and enhanced nuclease resistance. 2'-O,4'-C-Methylene-bridged nucleic acid/locked nucleic acid (2',4'-BNA/LNA) with 1,3-diaza-2-oxophenoxazine (BNAP (BH )) was previously reported. Herein, a novel BH analogue, 2',4'-BNA/LNA with 9-(2-aminoethoxy)-1,3-diaza-2-oxophenoxazine (G-clamp), named BNAP-AEO (BAEO ), was designed. The BAEO nucleoside was successfully synthesized and incorporated into oligodeoxynucleotides (ODNs). ODNs containing BAEO possessed up to 104 -, 152-, and 11-fold higher binding affinities for complementary (c) RNA than those of ODNs containing 2'-deoxycytidine (C), 2',4'-BNA/LNA with 5-methylcytosine (L), or 2'-deoxyribonucleoside with G-clamp (PAEO ), respectively. Moreover, duplexes formed by ODN bearing BAEO with cDNA and cRNA were thermally stable, even under molecular crowding conditions induced by the addition of polyethylene glycol. Furthermore, ODN bearing BAEO was more resistant to 3'-exonuclease than ODNs with phosphorothioate linkages.
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Affiliation(s)
- Yuki Kishimoto
- Graduate School of Pharmaceutical SciencesOsaka University1–6 Yamadaoka SuitaOsaka565-0871Japan
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
| | - Osamu Nakagawa
- Graduate School of Pharmaceutical SciencesOsaka University1–6 Yamadaoka SuitaOsaka565-0871Japan
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
- Faculty of Pharmaceutical SciencesTokushima Bunri University180 Nishihamahoji, Yamashiro-choTokushima770-8514Japan
| | - Akane Fujii
- Graduate School of Pharmaceutical SciencesOsaka University1–6 Yamadaoka SuitaOsaka565-0871Japan
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
| | - Kotaro Yoshioka
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
- Department of Neurology and Neurological ScienceGraduate School of Medical and Dental SciencesTokyo Medical and Dental University1-5-45 Yushima, Bunkyo-kuTokyo113-8519Japan
| | - Tetsuya Nagata
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
- Department of Neurology and Neurological ScienceGraduate School of Medical and Dental SciencesTokyo Medical and Dental University1-5-45 Yushima, Bunkyo-kuTokyo113-8519Japan
| | - Takanori Yokota
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
- Department of Neurology and Neurological ScienceGraduate School of Medical and Dental SciencesTokyo Medical and Dental University1-5-45 Yushima, Bunkyo-kuTokyo113-8519Japan
| | - Yoshiyuki Hari
- Faculty of Pharmaceutical SciencesTokushima Bunri University180 Nishihamahoji, Yamashiro-choTokushima770-8514Japan
| | - Satoshi Obika
- Graduate School of Pharmaceutical SciencesOsaka University1–6 Yamadaoka SuitaOsaka565-0871Japan
- Core Research for Evolutional Science and Technology (CREST), (Japan) Sciences and Technology Agency (JST)7 GobanchoChiyoda-kuTokyo102-0076Japan
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12
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Feng Y, Shu J, Yao L, Lan Y, Ye L, Mei W, Ding Y. Recognizing and stabilizing miR-21 by chiral ruthenium(II) complexes. BMC Chem 2020; 14:26. [PMID: 32266333 PMCID: PMC7119291 DOI: 10.1186/s13065-020-00672-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 03/09/2020] [Indexed: 12/19/2022] Open
Abstract
MiR-21, a non-coding miRNA with 22 nucleotides, plays an important part in the proliferation, invasion, and metastasis of tumor cells. The present study demonstrates that isomers of chiral ruthenium(II) complexes with alkynes (Λ-1 and Δ-1) were synthesized by Songogashira coupling reaction by using microwave-assisted synthetic technology. The isomers can recognize and stabilize miR-21, with the Λ-isomer showing a stronger binding capacity than the Δ-isomer. Further studies showed that both isomers can be uptaken by MDA-MB-231 cells and enriched in the nucleus. Treatment with the Λ-/Δ-isomer downregulated the expression of miR-21. In a word, the development of chiral ruthenium(II) complexes act as potential inhibitors against tumor cells by recognizing, stabilizing, and regulating the expression of miR-21.
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Affiliation(s)
- Yin Feng
- The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, 510062 China
| | - Jing Shu
- School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, 510006 China
- Guangdong Province Engineering Center for Molecular Probe & Biomedical Imaging, Guangzhou, 510006 China
| | - Liangzhong Yao
- The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, 510062 China
| | - Yutao Lan
- Guangdong Province Engineering Center for Molecular Probe & Biomedical Imaging, Guangzhou, 510006 China
- School of Nursing, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006 China
| | - Lianbao Ye
- School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, 510006 China
- Guangdong Province Engineering Center for Molecular Probe & Biomedical Imaging, Guangzhou, 510006 China
- Guangzhou Key Laboratory of Construction and Application of New Drug Screening Model System, Guangdong Pharmaceutical University, Guangzhou, 510006 China
| | - Wenjie Mei
- School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou, 510006 China
- Guangdong Province Engineering Center for Molecular Probe & Biomedical Imaging, Guangzhou, 510006 China
- Guangzhou Key Laboratory of Construction and Application of New Drug Screening Model System, Guangdong Pharmaceutical University, Guangzhou, 510006 China
| | - Ying Ding
- The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, 510062 China
- Guangdong Province Engineering Center for Molecular Probe & Biomedical Imaging, Guangzhou, 510006 China
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13
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Hirashima S, Sugiyama H, Park S. Construction of a FRET System in a Double-Stranded DNA Using Fluorescent Thymidine and Cytidine Analogs. J Phys Chem B 2020; 124:8794-8800. [DOI: 10.1021/acs.jpcb.0c06879] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Shingo Hirashima
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Soyoung Park
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
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14
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Juliusson HY, Sigurdsson ST. Reduction Resistant and Rigid Nitroxide Spin-Labels for DNA and RNA. J Org Chem 2020; 85:4036-4046. [PMID: 32103670 DOI: 10.1021/acs.joc.9b02988] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy, coupled with site-directed spin labeling (SDSL), is a useful method for studying conformational changes of biomolecules in cells. To employ in-cell EPR using nitroxide-based spin labels, the structure of the nitroxides must confer reduction resistance to withstand the reductive environment within cells. Here, we report the synthesis of two new spin labels, EÇ and EÇm, both of which possess the rigidity and the reduction resistance needed for extracting detailed structural information by EPR spectroscopy. EÇ and EÇm were incorporated into DNA and RNA, respectively, by oligonucleotide synthesis. Both labels were shown to be nonperturbing of the duplex structure. The partial reduction of EÇm during RNA synthesis was circumvented by the protection of the nitroxide as a benzoylated hydroxylamine.
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Affiliation(s)
- Haraldur Y Juliusson
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland
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15
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Cai J, Ding L, Gong P, Huang J. A colorimetric detection of microRNA-148a in gastric cancer by gold nanoparticle-RNA conjugates. NANOTECHNOLOGY 2020; 31:095501. [PMID: 31703221 DOI: 10.1088/1361-6528/ab55b7] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
For the early diagnosis of gastric cancer, microRNA-148a (miRNA-148a) as a promising biomarker is measured by a simple colorimetric biosensor due to its unique surface plasmon resonance (SPR) absorption of gold nanoparticles (AuNPs). In the assay system, the sensing probes are facilitated by the conjugation of AuNPs with RNA probes (RNAP) via Au-S bonds, which align in a tail-to-tail fashion onto the target RNA. When miRNA-148a is introduced, a sandwich hybridization reaction is triggered between the AuNP-RNAP conjugates and targets, resulting in changes in the SPR absorption band, microscopic distribution and macroscopic color of the AuNP solution. Following this principle, this colorimetric method is able to quantitatively detect miRNA-148a at nanomolar level with a limit of ∼1.9 nM, and exhibits high sensitivity and selectivity by a low-cost UV-vis spectrometer or even the naked eye. Moreover, the AuNP network materials with a characteristic sharp 'melting transition' provide significant guidance for the reusability of DNA or RNA biosensors.
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Affiliation(s)
- Jun Cai
- National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan, 430070, People's Republic of China
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16
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He J, Zhang Y, Chen Z, Li C, Yuan R, Xu W. Targeted DNA-driven catalytic assembly light-up ratiometric fluorescence of biemissive silver nanoclusters for amplified biosensing. Chem Commun (Camb) 2020; 56:10325-10328. [DOI: 10.1039/d0cc04055j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We report a ratiometric fluorescence strategy using biemissive silver nanoclusters that are harbored in a functional hairpin beacon for rapid, specific and sensitive detection of specific HIV-related DNA as a model.
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Affiliation(s)
- Jiayang He
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
| | - Yuxuan Zhang
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
| | - Zehui Chen
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
| | - Chong Li
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
| | - Ruo Yuan
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
| | - Wenju Xu
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University)
- Ministry of Education
- School of Chemistry and Chemical Engineering
- Southwest University
- Chongqing 400715
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17
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Lawson CP, Füchtbauer AF, Wranne MS, Giraud T, Floyd T, Dumat B, Andersen NK, H El-Sagheer A, Brown T, Gradén H, Wilhelmsson LM, Grøtli M. Synthesis, oligonucleotide incorporation and fluorescence properties in DNA of a bicyclic thymine analogue. Sci Rep 2018; 8:13970. [PMID: 30228309 PMCID: PMC6143597 DOI: 10.1038/s41598-018-31897-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/23/2018] [Indexed: 12/26/2022] Open
Abstract
Fluorescent base analogues (FBAs) have emerged as a powerful class of molecular reporters of location and environment for nucleic acids. In our overall mission to develop bright and useful FBAs for all natural nucleobases, herein we describe the synthesis and thorough characterization of bicyclic thymidine (bT), both as a monomer and when incorporated into DNA. We have developed a robust synthetic route for the preparation of the bT DNA monomer and the corresponding protected phosphoramidite for solid-phase DNA synthesis. The bT deoxyribonucleoside has a brightness value of 790 M−1cm−1 in water, which is comparable or higher than most fluorescent thymine analogues reported. When incorporated into DNA, bT pairs selectively with adenine without perturbing the B-form structure, keeping the melting thermodynamics of the B-form duplex DNA virtually unchanged. As for most fluorescent base analogues, the emission of bT is reduced inside DNA (4.5- and 13-fold in single- and double-stranded DNA, respectively). Overall, these properties make bT an interesting thymine analogue for studying DNA and an excellent starting point for the development of brighter bT derivatives.
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Affiliation(s)
- Christopher P Lawson
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden
| | - Anders F Füchtbauer
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Moa S Wranne
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Tristan Giraud
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Thomas Floyd
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Blaise Dumat
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Nicolai K Andersen
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Afaf H El-Sagheer
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.,Chemistry Branch, Department of Science and Mathematics, Faculty of Petroleum and Mining Engineering, Suez University, Suez, 43721, Egypt
| | - Tom Brown
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Henrik Gradén
- Cardiovascular, Renal and Metabolic Diseases IMED Biotech Unit, AstraZeneca Gothenburg, Pepparedsleden 1, Molndal, SE-431 83, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - Morten Grøtli
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden.
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18
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Kishimoto Y, Fujii A, Nakagawa O, Nagata T, Yokota T, Hari Y, Obika S. Synthesis and thermal stabilities of oligonucleotides containing 2'-O,4'-C-methylene bridged nucleic acid with a phenoxazine base. Org Biomol Chem 2018; 15:8145-8152. [PMID: 28920119 DOI: 10.1039/c7ob01874f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We designed and synthesized a novel artificial 2'-O,4'-C-methylene bridged nucleic acid (2',4'-BNA/LNA) with a phenoxazine nucleobase and named this compound BNAP. Oligodeoxynucleotide (ODN) containing BNAP showed higher binding affinities toward complementary DNA and RNA as compared to ODNs bearing 2',4'-BNA/LNA with 5-methylcytosine or 2'-deoxyribonucleoside with phenoxazine. Thermodynamic analysis revealed that BNAP exhibits properties associated with the phenoxazine moiety in DNA/DNA duplexes and characteristics associated with the 2',4'-BNA/LNA moiety in DNA/RNA duplexes.
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Affiliation(s)
- Yuki Kishimoto
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
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19
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Bood M, Sarangamath S, Wranne MS, Grøtli M, Wilhelmsson LM. Fluorescent nucleobase analogues for base-base FRET in nucleic acids: synthesis, photophysics and applications. Beilstein J Org Chem 2018; 14:114-129. [PMID: 29441135 PMCID: PMC5789401 DOI: 10.3762/bjoc.14.7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/22/2017] [Indexed: 12/31/2022] Open
Abstract
Förster resonance energy transfer (FRET) between a donor nucleobase analogue and an acceptor nucleobase analogue, base–base FRET, works as a spectroscopic ruler and protractor. With their firm stacking and ability to replace the natural nucleic acid bases inside the base-stack, base analogue donor and acceptor molecules complement external fluorophores like the Cy-, Alexa- and ATTO-dyes and enable detailed investigations of structure and dynamics of nucleic acid containing systems. The first base–base FRET pair, tCO–tCnitro, has recently been complemented with among others the adenine analogue FRET pair, qAN1–qAnitro, increasing the flexibility of the methodology. Here we present the design, synthesis, photophysical characterization and use of such base analogues. They enable a higher control of the FRET orientation factor, κ2, have a different distance window of opportunity than external fluorophores, and, thus, have the potential to facilitate better structure resolution. Netropsin DNA binding and the B-to-Z-DNA transition are examples of structure investigations that recently have been performed using base–base FRET and that are described here. Base–base FRET has been around for less than a decade, only in 2017 expanded beyond one FRET pair, and represents a highly promising structure and dynamics methodology for the field of nucleic acids. Here we bring up its advantages as well as disadvantages and touch upon potential future applications.
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Affiliation(s)
- Mattias Bood
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Sangamesh Sarangamath
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Moa S Wranne
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Morten Grøtli
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
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20
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Ro JJ, Go GH, Wilhelmsson LM, Kim BH. Fluorescence properties of 6-aryl-2'-deoxy-furanouridine and -pyrrolocytidine and their derivatives. Methods Appl Fluoresc 2017; 6:015004. [PMID: 28933349 DOI: 10.1088/2050-6120/aa8e19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
2'-deoxyfuranouridine derivatives presenting various aryl groups have been synthesized through Cu(I)-catalyzed intramolecular cyclizations. Moreover, corresponding pyrrolo-dC derivatives have been synthesized and both families of compounds thoroughly characterized using UV/vis and fluorescence spectroscopy as well as time-dependent density functional theory calculations. The photophysical characterization, show that our newly synthesized derivatives of the important pyrrolo-dC family have high fluorescence quantum yields (QYs) and brightness values. Pyrrolo-dC derivative, 3a, shows an environment sensitive QY of up to >60% and brightness of almost 3000, in low polarity solvents and excitation and emission maxima between 365-381 nm and 479-510 nm, respectively, in solvents of different polarities. Two other derivatives, 3b and 3c, show high QYs and brightness values of up to 3300 that are fairly insensitive to their microenvironment. These promising photophysical features suggest future applicability as fluorescent nucleobase analogs.
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Affiliation(s)
- Jong Jin Ro
- Department of Chemistry, Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
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21
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Mei H, Shi C, Jimenez RM, Wang Y, Kardouh M, Chaput JC. Synthesis and polymerase activity of a fluorescent cytidine TNA triphosphate analogue. Nucleic Acids Res 2017; 45:5629-5638. [PMID: 28472363 PMCID: PMC5449585 DOI: 10.1093/nar/gkx368] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 04/21/2017] [Indexed: 02/04/2023] Open
Abstract
Threose nucleic acid (TNA) is an artificial genetic polymer capable of undergoing Darwinian evolution to produce aptamers with affinity to specific targets. This property, coupled with a backbone structure that is refractory to nuclease digestion, makes TNA an attractive biopolymer system for diagnostic and therapeutic applications. Expanding the chemical diversity of TNA beyond the natural bases would enable the development of functional TNA molecules with enhanced physiochemical properties. Here, we describe the synthesis and polymerase activity of a fluorescent cytidine TNA triphosphate analogue (1,3-diaza-2-oxo-phenothiazine, tCfTP) that maintains Watson-Crick base pairing with guanine. Polymerase-mediated primer-extension assays reveal that tCfTP is efficiently added to the growing end of a TNA primer. Detailed kinetic assays indicate that tCfTP and tCTP have comparable rates for the first nucleotide incorporation step (kobs1). However, addition of the second nucleotide (kobs2) is 700-fold faster for tCfTP than tCTP due the increased effects of base stacking. Last, we found that TNA replication using tCfTP in place of tCTP exhibits 98.4% overall fidelity for the combined process of TNA transcription and reverse transcription. Together, these results expand the chemical diversity of enzymatically generated TNA molecules to include a hydrophobic base analogue with strong fluorescent properties that is compatible with in vitro selection.
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Affiliation(s)
- Hui Mei
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Changhua Shi
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Randi M Jimenez
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Yajun Wang
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - Miramar Kardouh
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
| | - John C Chaput
- Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3958, USA
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22
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Wranne MS, Füchtbauer AF, Dumat B, Bood M, El-Sagheer AH, Brown T, Gradén H, Grøtli M, Wilhelmsson LM. Toward Complete Sequence Flexibility of Nucleic Acid Base Analogue FRET. J Am Chem Soc 2017; 139:9271-9280. [PMID: 28613885 DOI: 10.1021/jacs.7b04517] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Förster resonance energy transfer (FRET) using fluorescent base analogues is a powerful means of obtaining high-resolution nucleic acid structure and dynamics information that favorably complements techniques such as NMR and X-ray crystallography. Here, we expand the base-base FRET repertoire with an adenine analogue FRET-pair. Phosphoramidite-protected quadracyclic 2'-deoxyadenosine analogues qAN1 (donor) and qAnitro (acceptor) were synthesized and incorporated into DNA by a generic, reliable, and high-yielding route, and both constitute excellent adenine analogues. The donor, qAN1, has quantum yields reaching 21% and 11% in single- and double-strands, respectively. To the best of our knowledge, this results in the highest average brightness of an adenine analogue inside DNA. Its potent emissive features overlap well with the absorption of qAnitro and thus enable accurate FRET-measurements over more than one turn of B-DNA. As we have shown previously for our cytosine analogue FRET-pair, FRET between qAN1 and qAnitro positioned at different base separations inside DNA results in efficiencies that are highly dependent on both distance and orientation. This facilitates significantly enhanced resolution in FRET structure determinations, demonstrated here in a study of conformational changes of DNA upon binding of the minor groove binder netropsin. Finally, we note that the donor and acceptor of our cytosine FRET-pair, tCO and tCnitro, can be conveniently combined with the acceptor and donor of our current adenine pair, respectively. Consequently, our base analogues can now measure base-base FRET between 3 of the 10 possible base combinations and, through base-complementarity, between all sequence positions in a duplex.
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Affiliation(s)
- Moa S Wranne
- Department of Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology , Gothenburg S-41296, Sweden
| | - Anders Foller Füchtbauer
- Department of Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology , Gothenburg S-41296, Sweden
| | - Blaise Dumat
- Department of Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology , Gothenburg S-41296, Sweden
| | - Mattias Bood
- Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg S-41296, Sweden.,Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development, AstraZeneca , Mölndal S-43183, Sweden
| | - Afaf H El-Sagheer
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Oxford OX1 3TA, United Kingdom.,Chemistry Branch, Faculty of Petroleum and Mining Engineering, Suez University , Suez 43721, Egypt
| | - Tom Brown
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford , Oxford OX1 3TA, United Kingdom
| | - Henrik Gradén
- Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development, AstraZeneca , Mölndal S-43183, Sweden
| | - Morten Grøtli
- Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg S-41296, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology , Gothenburg S-41296, Sweden
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23
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Füchtbauer AF, Preus S, Börjesson K, McPhee SA, Lilley DMJ, Wilhelmsson LM. Fluorescent RNA cytosine analogue - an internal probe for detailed structure and dynamics investigations. Sci Rep 2017; 7:2393. [PMID: 28539582 PMCID: PMC5443824 DOI: 10.1038/s41598-017-02453-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 04/10/2017] [Indexed: 12/22/2022] Open
Abstract
The bright fluorescent cytosine analogue tCO stands out among fluorescent bases due to its virtually unquenched fluorescence emission in duplex DNA. However, like most reported base analogues, it has not been thoroughly characterized in RNA. We here report on the first synthesis and RNA-incorporation of tCO, and characterize its base-mimicking and fluorescence properties in RNA. As in DNA, we find a high quantum yield inside RNA duplexes (<ΦF> = 0.22) that is virtually unaffected by the neighbouring bases (ΦF = 0.20-0.25), resulting in an average brightness of 1900 M-1 cm-1. The average fluorescence lifetime in RNA duplexes is 4.3 ns and generally two lifetimes are required to fit the exponential decays. Fluorescence properties in ssRNA are defined by a small increase in average quantum yield (<ΦF > = 0.24) compared to dsRNA, with a broader distribution (ΦF = 0.17-0.34) and slightly shorter average lifetimes. Using circular dichroism, we find that the tCO-modified RNA duplexes form regular A-form helices and in UV-melting experiments the stability of the duplexes is only slightly higher than that of the corresponding natural RNA (<ΔT m> = + 2.3 °C). These properties make tCO a highly interesting fluorescent RNA base analogue for detailed FRET-based structural measurements, as a bright internal label in microscopy, and for fluorescence anisotropy measurements of RNA dynamics.
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Affiliation(s)
- Anders Foller Füchtbauer
- Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-41296, Sweden
| | - Søren Preus
- Department of Chemistry, University of Copenhagen, Copenhagen, DK-2100, Denmark
| | - Karl Börjesson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, SE-41296, Sweden
| | - Scott A McPhee
- Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - David M J Lilley
- Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - L Marcus Wilhelmsson
- Chemistry and Chemical Engineering/Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-41296, Sweden.
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24
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Han JH, Yamamoto S, Park S, Sugiyama H. Development of a Vivid FRET System Based on a Highly Emissive dG-dC Analogue Pair. Chemistry 2017; 23:7607-7613. [PMID: 28411372 DOI: 10.1002/chem.201701118] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Indexed: 12/12/2022]
Abstract
A new type of Förster Resonance Energy Transfer (FRET) system using highly emissive isomorphic nucleobase analogues is reported. The FRET pair consists of 2-aminothieno[3,4-d]pyrimidine G-mimic deoxyribonucleoside (th dG) as an energy donor and 1,3-diaza-2-oxophenothiazine (tC) as an energy acceptor. The distance and orientation between donor and acceptor was controlled by systematic incorporation of th dG and tC into DNA sequences to investigate the FRET efficiencies. This is the first Watson-Crick base-pairable FRET pair to produce vivid colors. In addition, this nucleic acid-based FRET pair was used to monitor DNA conformation and achieved visualization of the B-Z transition.
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Affiliation(s)
- Ji Hoon Han
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Seigi Yamamoto
- Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima, 770-8505, Japan
| | - Soyoung Park
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan.,Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University,Yoshida-ushinomiyacho, Sakyo-ku, Kyoto, 606-8501, Japan
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25
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Bielecka P, Juskowiak B. Fluorescent Sensor for PH Monitoring Based on an i-Motif---Switching Aptamer Containing a Tricyclic Cytosine Analogue (tC). Molecules 2015; 20:18511-25. [PMID: 26473815 PMCID: PMC6332284 DOI: 10.3390/molecules201018511] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 09/24/2015] [Accepted: 10/06/2015] [Indexed: 12/16/2022] Open
Abstract
There are cytosine-rich regions in the genome that bind protons with high specificity. Thus protonated C-rich sequence may undergo folding to tetraplex structures called i-motifs. Therefore, one can regard such specific C-rich oligonucleotides as aptamers that recognize protons and undergo conformational transitions. Proper labeling of the aptamer with a fluorescent tag constitutes a platform to construct a pH-sensitive aptasensor. Since the hemiprotonated C-C⁺ base pairs are responsible for the folded tetraplex structure of i-motif, we decided to substitute one of cytosines in an aptamer sequence with its fluorescent analogue, 1,3-diaza-2-oxophenothiazine (tC). In this paper we report on three tC-modified fluorescent probes that contain RET related sequences as a proton recognizing aptamer. Results of the circular dichroism (CD), UV absorption melting experiments, and steady-state fluorescence measurements of these tC-modified i-motif probes are presented and discussed. The pH-induced i-motif formation by the probes resulted in fluorescence quenching of tC fluorophore. Efficiency of quenching was related to the pH variations. Suitability of the sensor for monitoring pH changes was also demonstrated.
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Affiliation(s)
- Patrycja Bielecka
- Laboratory of Bioanalytical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b 61-614 Poznan, Poland.
| | - Bernard Juskowiak
- Laboratory of Bioanalytical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b 61-614 Poznan, Poland.
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26
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2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface. Q Rev Biophys 2015; 48:244-79. [DOI: 10.1017/s0033583514000158] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractNearly 50 years since its potential as a fluorescent base analogue was first recognized, 2-aminopurine (2AP) continues to be the most widely used fluorescent probe of DNA structure and the perturbation of that structure by interaction with enzymes and other molecules. In this review, we begin by considering the origin of the dramatic and intriguing difference in photophysical properties between 2AP and its structural isomer, adenine; although 2AP differs from the natural base only in the position of the exocyclic amine group, its fluorescence intensity is one thousand times greater. We then discuss the mechanism of interbase quenching of 2AP fluorescence in DNA, which is the basis of its use as a conformational probe but remains imperfectly understood. There are hundreds of examples in the literature of the use of changes in the fluorescence intensity of 2AP as the basis of assays of conformational change; however, in this review we will consider in detail only a few intensity-based studies. Our primary aim is to highlight the use of time-resolved fluorescence measurements, and the interpretation of fluorescence decay parameters, to explore the structure and dynamics of DNA. We discuss the salient features of the fluorescence decay of 2AP when incorporated in DNA and review the use of decay measurements in studying duplexes, single strands and other structures. We survey the use of 2AP as a probe of DNA-enzyme interaction and enzyme-induced distortion, focusing particularly on its use to study base flipping and the enhanced mechanistic insights that can be gained by a detailed analysis of the decay parameters, rather than merely monitoring changes in fluorescence intensity. Finally we reflect on the merits and shortcomings of 2AP and the prospects for its wider adoption as a fluorescence-decay-based probe.
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27
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Antibody mediated fluorescence enhancement of nucleoside analogue 1,3-diaza-2-oxophenoxazine (tC°). Talanta 2014; 124:67-70. [PMID: 24767447 DOI: 10.1016/j.talanta.2014.02.046] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 02/14/2014] [Accepted: 02/20/2014] [Indexed: 11/20/2022]
Abstract
We report on the generation and analytical application of the monoclonal antibody G93-ED2 raised against the tricyclic fluorescent nucleoside analogue 1,3-diaza-2-oxophenoxazine (tC°). G93-ED2 is specifically binding this deoxycytidine analogue and was found to raise its fluorescence intensity by a factor of 5. This unique feature makes it a valuable tool in fluorescence dependent immunoassays. G93-ED2 was successfully applied in a homogeneous fluorescence quenching immunoassay (DNA-Q) for the sequence specific determination of DNA.
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29
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Rodgers BJ, Elsharif NA, Vashisht N, Mingus MM, Mulvahill MA, Stengel G, Kuchta RD, Purse BW. Functionalized tricyclic cytosine analogues provide nucleoside fluorophores with improved photophysical properties and a range of solvent sensitivities. Chemistry 2013; 20:2010-5. [PMID: 24311229 DOI: 10.1002/chem.201303410] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Indexed: 12/11/2022]
Abstract
Tricyclic cytosines (tC and tC(O) frameworks) have emerged as a unique class of fluorescent nucleobase analogues that minimally perturb the structure of B-form DNA and that are not quenched in duplex nucleic acids. Systematic derivatization of these frameworks is a likely approach to improve on and diversify photophysical properties, but has not so far been examined. Synthetic methods were refined to improve on tolerance for electron-donating and electron-withdrawing groups, resulting in a series of eight new, fluorescent cytidine analogues. Photophysical studies show that substitution of the framework results in a pattern of effects largely consistent across tC and tC(O) and provides nucleoside fluorophores that are brighter than either parent. Moreover, a range of solvent sensitivities is observed, offering promise that this family of probes can be extended to new applications that require reporting on the local environment.
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Affiliation(s)
- Brittney J Rodgers
- Department of Chemistry and Biochemistry, University of Denver, 2199 S. University Blvd., Denver, CO 80208 (USA)
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30
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Preus S, Jønck S, Pittelkow M, Dierckx A, Karpkird T, Albinsson B, Wilhelmsson LM. The photoinduced transformation of fluorescent DNA base analogue tC triggers DNA melting. Photochem Photobiol Sci 2013; 12:1416-22. [PMID: 23689311 DOI: 10.1039/c3pp50057h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
While fluorescent analogues of the canonical nucleobases have proven to be highly valuable in a large number of applications, up until today, fluorescent DNA base analogues remain virtually inapplicable for single-molecule fluorescence experiments which require extremely bright and photostable dyes. Insight into the photodegradation processes of these fluorophores is thus a key step in the continuous development towards dyes with improved performances. Here, we show that the commercially available fluorescent nucleobase analogue tC under intense long-term illumination and in the presence of O2 is degraded to form a single photoreaction product which we suggest to be the sulfoxide form of tC. The photoproduct is characterized by a blue-shifted absorption and a less intense fluorescence compared to that of tC. Interestingly, when tC is positioned inside double-stranded DNA this photodriven conversion of tC to its photoproduct greatly reduces the duplex stability of the overall double helix in which the probe is positioned. Since tC can be excited selectively at 400 nm, well outside the absorption band of the natural DNA bases, this observation points towards the application of tC as a general light-triggered switch of DNA duplex stability.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, Copenhagen, DK-2100, Denmark
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31
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Segal M, Yavin E, Kafri P, Shav-Tal Y, Fischer B. Detection of mRNA of the cyclin D1 breast cancer marker by a novel duplex-DNA probe. J Med Chem 2013; 56:4860-9. [PMID: 23688195 DOI: 10.1021/jm301838y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Previously, we have described 5-((4-methoxy-phenyl)-trans-vinyl)-2'-deoxy-uridine, 6, as a fluorescent uridine analogue exhibiting a 3000-fold higher quantum yield (Φ 0.12) and maximum emission (478 nm) which is 170 nm red-shifted as compared to uridine. Here, we utilized 6 for preparation of labeled oligodeoxynucleotide (ODN) probes based on MS2 and cyclin D1 (a known breast cancer mRNA marker) sequences. Cyclin D1-derived labeled-ssODN showed a 9.5-fold decrease of quantum yield upon duplex formation. On the basis of this finding, we developed the ds-NIF (nucleoside with intrinsic fluorescence)-probe methodology for detection of cyclin D1 mRNA, by which the fluorescent probe is released upon recognition of target mRNA by the relatively dark NIF-duplex-probe. Indeed, we successfully detected, a ss-deoxynucleic acid (DNA) variant of cyclin D1 mRNA using a dark NIF-labeled duplex-probe, and monitoring the recognition process by fluorescence spectroscopy and gel electrophoresis. Furthermore, we successfully detected cyclin D1 mRNA in RNA extracted from cancerous human cells, using ds-NIF methodology.
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Affiliation(s)
- Meirav Segal
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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32
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Widom JR, Rappoport D, Perdomo-Ortiz A, Thomsen H, Johnson NP, von Hippel PH, Aspuru-Guzik A, Marcus AH. Electronic transition moments of 6-methyl isoxanthopterin--a fluorescent analogue of the nucleic acid base guanine. Nucleic Acids Res 2012. [PMID: 23185042 PMCID: PMC3553960 DOI: 10.1093/nar/gks1148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Fluorescent nucleic acid base analogues are important spectroscopic tools for understanding local structure and dynamics of DNA and RNA. We studied the orientations and magnitudes of the electric dipole transition moments (EDTMs) of 6-methyl isoxanthopterin (6-MI), a fluorescent analogue of guanine that has been particularly useful in biological studies. Using a combination of absorption spectroscopy, linear dichroism (LD) and quantum chemical calculations, we identified six electronic transitions that occur within the 25 000–50 000 cm−1 spectral range. Our results indicate that the two experimentally observed lowest-energy transitions, which occur at 29 687 cm−1 (337 nm) and 34 596 cm−1 (289 nm), are each polarized within the plane of the 6-MI base. A third in-plane polarized transition is experimentally observed at 47 547 cm−1 (210 nm). The theoretically predicted orientation of the lowest-energy transition moment agrees well with experiment. Based on these results, we constructed an exciton model to describe the absorption spectra of a 6-MI dinucleotide–substituted double-stranded DNA construct. This model is in good agreement with the experimental data. The orientations and intensities of the low-energy electronic transitions of 6-MI reported here should be useful for studying local conformations of DNA and RNA in biologically important complexes.
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Affiliation(s)
- Julia R Widom
- Oregon Center for Optics, Department of Chemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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33
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Preus S, Wilhelmsson LM. Advances in quantitative FRET-based methods for studying nucleic acids. Chembiochem 2012; 13:1990-2001. [PMID: 22936620 DOI: 10.1002/cbic.201200400] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Indexed: 01/02/2023]
Abstract
Förster resonance energy transfer (FRET) is a powerful tool for monitoring molecular distances and interactions at the nanoscale level. The strong dependence of transfer efficiency on probe separation makes FRET perfectly suited for "on/off" experiments. To use FRET to obtain quantitative distances and three-dimensional structures, however, is more challenging. This review summarises recent studies and technological advances that have improved FRET as a quantitative molecular ruler in nucleic acid systems, both at the ensemble and at the single-molecule levels.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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34
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Xia S, Beckman J, Wang J, Konigsberg WH. Using a fluorescent cytosine analogue tC(o) to probe the effect of the Y567 to Ala substitution on the preinsertion steps of dNMP incorporation by RB69 DNA polymerase. Biochemistry 2012; 51:4609-17. [PMID: 22616982 PMCID: PMC3437246 DOI: 10.1021/bi300241m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Residues in the nascent base pair binding pocket (NBP) of bacteriophage RB69 DNA polymerase (RB69pol) are responsible for base discrimination. Replacing Tyr567 with Ala leads to greater flexibility in the NBP, increasing the probability of misincorporation. We used the fluorescent cytosine analogue, 1,3-diaza-2-oxophenoxazine (tC(o)), to identify preinsertion step(s) altered by NBP flexibility. When tC(o) is the templating base in a wild-type (wt) RB69pol ternary complex, its fluorescence is quenched only in the presence of dGTP. However, with the RB69pol Y567A mutant, the fluorescence of tC(o) is also quenched in the presence of dATP. We determined the crystal structure of the dATP/tC(o)-containing ternary complex of the RB69pol Y567A mutant at 1.9 Å resolution and found that the incoming dATP formed two hydrogen bonds with an imino-tautomerized form of tC(o). Stabilization of the dATP/tC(o) base pair involved movement of the tC(o) backbone sugar into the DNA minor groove and required tilting of the tC(o) tricyclic ring to prevent a steric clash with L561. This structure, together with the pre-steady-state kinetic parameters and dNTP binding affinity, estimated from equilibrium fluorescence titrations, suggested that the flexibility of the NBP, provided by the Y567 to Ala substitution, led to a more favorable forward isomerization step resulting in an increase in dNTP binding affinity.
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Affiliation(s)
| | | | | | - William H. Konigsberg
- Corresponding author: Prof. William H. Konigsberg SHM CE-14 Department of Molecular Biophysics and Biochemistry Yale University New Haven, CT 06520-8114 Telephone: (203) 785-4599 Fax: (203) 785-7979
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35
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Neelakandan PP, McCullagh M, Schatz GC, Lewis FD. Electronic interactions in helical stacked arrays of the modified DNA base pyrrolocytosine. J Phys Chem B 2012; 116:5199-204. [PMID: 22486518 DOI: 10.1021/jp302385c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The thermal stability and ultraviolet and circular dichroism spectra of nine synthetic DNA hairpins possessing one or more (P)C-G base pairs ((P)C = pyrrolocytosine) have been investigated. One group of hairpins possess 1-5 sequential (P)C-G base pairs while another group possess two (P)C-G base pairs separated by 1-3 A-T base pairs. The first group displays a nearly linear dependence of UV and exciton-coupled circular dichroism (EC-CD) band intensity upon the number of neighboring chromophores, whereas the second group shows weak EC-CD only at the shortest distances between non-neighboring chromophores. This result stands in marked contrast to the exciton coupling seen between stilbene chromophores separated by as many as a dozen base pairs. The weak exciton coupling between non-neighboring (P)C chromophores, like that of the natural nucelobases, is attributed to their relatively weak electronic transition dipoles.
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Affiliation(s)
- Prakash P Neelakandan
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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36
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Dierckx A, Miannay FA, Ben Gaied N, Preus S, Björck M, Brown T, Wilhelmsson LM. Quadracyclic adenine: a non-perturbing fluorescent adenine analogue. Chemistry 2012; 18:5987-97. [PMID: 22437923 DOI: 10.1002/chem.201103419] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Indexed: 12/26/2022]
Abstract
Fluorescent-base analogues (FBAs) comprise a group of increasingly important molecules for the investigation of nucleic acid structure and dynamics as well as of interactions between nucleic acids and other molecules. Here, we report on the synthesis, detailed spectroscopic characterisation and base-pairing properties of a new environment-sensitive fluorescent adenine analogue, quadracyclic adenine (qA). After developing an efficient route of synthesis for the phosphoramidite of qA it was incorporated into DNA in high yield by using standard solid-phase synthesis procedures. In DNA qA serves as an adenine analogue that preserves the B-form and, in contrast to most currently available FBAs, maintains or even increases the stability of the duplex. We demonstrate that, unlike fluorescent adenine analogues, such as the most commonly used one, 2-aminopurine, and the recently developed triazole adenine, qA shows highly specific base-pairing with thymine. Moreover, qA has an absorption band outside the absorption of the natural nucleobases (>300 nm) and can thus be selectively excited. Upon excitation the qA monomer displays a fluorescence quantum yield of 6.8 % with an emission maximum at 456 nm. More importantly, upon incorporation into DNA the fluorescence of qA is significantly less quenched than most FBAs. This results in quantum yields that in some sequences reach values that are up to fourfold higher than maximum values reported for 2-aminopurine. To facilitate future utilisation of qA in biochemical and biophysical studies we investigated its fluorescence properties in greater detail and resolved its absorption band outside the DNA absorption region into distinct transition dipole moments. In conclusion, the unique combination of properties of qA make it a promising alternative to current fluorescent adenine analogues for future detailed studies of nucleic acid-containing systems.
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Affiliation(s)
- Anke Dierckx
- Department of Chemical and Biological Engineering, Physical Chemistry, Chalmers University of Technology, 41296 Gothenburg, Sweden
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37
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Gill P, Ranjbar B, Saber R, Khajeh K, Mohammadian M. Biomolecular and structural analyses of cauliflower-like DNAs by ultraviolet, circular dichroism, and fluorescence spectroscopies in comparison with natural DNA. J Biomol Tech 2011; 22:60-6. [PMID: 21738438 PMCID: PMC3121149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Cauliflower-like DNAs are stem-loop DNAs that are fabricated periodically in inverted repetitions from deoxyribonucleic acid phosphates (dNTPs) by loop-mediated isothermal amplification (LAMP). Cauliflower-like DNAs have ladder-shape behaviors on gel electrophoresis, and increasing the time of LAMP leads to multiplying the repetitions, stem-loops, and electrophoretic bands. Cauliflower-like DNAs were fabricated via LAMP using two loop primers, two bumper primers, dNTPs, a λ-phage DNA template, and a Bst DNA polymerase in 75- and 90-min periods. These times led to manufacturing two types of cauliflower-like DNAs with different contents of inverted repetitions and stem-loops, which were clearly indicated by two comparable electrophoresis patterns in agarose gel. LAMP-fabricated DNAs and natural dsB-DNA (salmon genomic DNA) were dialyzed in Gomori phosphate buffer (10 mM, pH 7.4) to be isolated from salts, nucleotides, and primers. Dialyzed DNAs were studied using UV spectroscopy, circular dichroism spectropolarimetry, and fluorescence spectrophotometry. Structural analyses indicated reduction of the molecular ellipticity and extinction coefficients in comparison with B-DNA. Also, cauliflower-like DNAs demonstrated less intrinsic and more extrinsic fluorescence in comparison with natural DNA. The overwinding and lengthening of the cauliflower-like configurations of LAMP DNAs led to changes in physical parameters of this type of DNA in comparison with natural DNA. The results obtained introduced new biomolecular characteristics of DNA macromolecules fabricated within a LAMP process and show the effects of more inverted repeats and stem-loops, which are manufactured by lengthening the process.
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Affiliation(s)
| | | | - Reza Saber
- Nanotechnology Group, Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Khosro Khajeh
- Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran; and
| | - Mehdi Mohammadian
- Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran; and
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38
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Discrimination against the Cytosine Analog tC by Escherichia coli DNA Polymerase IV DinB. J Mol Biol 2011; 409:89-100. [DOI: 10.1016/j.jmb.2011.03.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 03/27/2011] [Accepted: 03/30/2011] [Indexed: 01/30/2023]
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39
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Stengel G, Purse BW, Kuchta RD. Effect of transition metal ions on the fluorescence and Taq-catalyzed polymerase chain reaction of tricyclic cytidine analogs. Anal Biochem 2011; 416:53-60. [PMID: 21600183 DOI: 10.1016/j.ab.2011.04.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 04/14/2011] [Accepted: 04/21/2011] [Indexed: 12/11/2022]
Abstract
The cytosine analogs 1,3-diaza-2-oxophenothiazine (tC) and 1,3-diaza-2-oxophenoxazine (tCo) stand out among fluorescent bases due to their unquenched fluorescence emission in double-stranded DNA. Recently, we reported a method for the generation of densely tCo-labeled DNA by polymerase chain reaction (PCR) that relied on the use of the extremely thermostable Deep Vent polymerase. We have now developed a protocol that employs the more commonly used Taq polymerase. Supplementing the PCR with Mn(2+) or Co(2+) ions dramatically increased the amount of tCo triphosphate (dtCoTP) incorporated and, thus, enhanced the brightness of the PCR products. The resulting PCR products could be easily detected in gels based on their intrinsic fluorescence. The Mn(2+) ions modulate the PCR by improving the bypass of template tCo and the overall catalytic efficiency. In contrast to the lower fidelity during tCo bypass, Mn(2+) improved the ability of Taq polymerase to distinguish between dtCoTP and dTTP when copying a template dA. Interestingly, Mn(2+) ions hardly affect the fluorescence emission of tC(o), whereas the coordination of Co(2+) ions with the phosphate groups of DNA and nucleotides statically quenches tC(o) fluorescence with small reciprocal Stern-Vollmer constants of 10-300μM.
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Affiliation(s)
- Gudrun Stengel
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA
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40
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Gardarsson H, Kale AS, Sigurdsson ST. Structure-function relationships of phenoxazine nucleosides for identification of mismatches in duplex DNA by fluorescence spectroscopy. Chembiochem 2011; 12:567-75. [PMID: 21322103 DOI: 10.1002/cbic.201000478] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2010] [Indexed: 12/13/2022]
Abstract
The effects of the flanking sequence on the mismatch-detection capabilities of the fluorescent nucleoside phenoxazine (tC(O)) were examined in a systematic fashion, and compared to the previously reported fluorescent, phenoxazine-based nucleoside Ç(f) . We see some similarities for the two fluorescent nucleosides, for example, the emission intensity of the C-mismatched duplex is always the highest, and a three-peak pattern in the spectrum emerges when the fluorosides are base-paired with A. However, phenoxazine was only able to distinguish a mismatch from the fully base-paired duplex in 11 out of 16 flanking sequences, and was able to identify each of the mismatches in six of those sequences. Therefore, tC(O) shows poorer discrimination of mismatches than was previously reported for Ç(f) , which could be used to identify all base-pairing partners in all immediately flanking sequences, albeit in some cases by using mercuric ions to selectively quench the emission of the T-mismatched duplex. The mercuric titration might resolve the overlap of fluorescence curves of tC(O) in some flanking sequences, but not for 5'-d(CtC(O) G) and 5'-d(TtC(O) A) due to overlap of A-mismatch and G-match fluorescence curves. A pH titration was performed on Ç(f) , tC(O) and a N5-methylated derivative of tC(O) , which showed that the emergence of the three-peak pattern is associated with the de-protonation of N5 in the fluorosides. We also show that neither the α- nor β-anomer of the phenothiazine nucleoside (tC) was able to detect a mismatch in any of the flanking sequences examined.
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41
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Dierckx A, Dinér P, El-Sagheer AH, Kumar JD, Brown T, Grøtli M, Wilhelmsson LM. Characterization of photophysical and base-mimicking properties of a novel fluorescent adenine analogue in DNA. Nucleic Acids Res 2011; 39:4513-24. [PMID: 21278417 PMCID: PMC3105426 DOI: 10.1093/nar/gkr010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To increase the diversity of fluorescent base analogues with improved properties, we here present the straightforward click-chemistry-based synthesis of a novel fluorescent adenine-analogue triazole adenine (AT) and its photophysical characterization inside DNA. AT shows promising properties compared to the widely used adenine analogue 2-aminopurine. Quantum yields reach >20% and >5% in single- and double-stranded DNA, respectively, and show dependence on neighbouring bases. Moreover, AT shows only a minor destabilization of DNA duplexes, comparable to 2-aminopurine, and circular dichroism investigations suggest that AT only causes minimal structural perturbations to normal B-DNA. Furthermore, we find that AT shows favourable base-pairing properties with thymine and more surprisingly also with normal adenine. In conclusion, AT shows strong potential as a new fluorescent adenine analogue for monitoring changes within its microenvironment in DNA.
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Affiliation(s)
- Anke Dierckx
- Department of Chemical and Biological Engineering/Physical Chemistry, Chalmers University of Technology, University of Gothenburg, S-41296 Gothenburg, Sweden
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42
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Edwards TE, Cekan P, Reginsson GW, Shelke SA, Ferré-D'Amaré AR, Schiemann O, Sigurdsson ST. Crystal structure of a DNA containing the planar, phenoxazine-derived bi-functional spectroscopic probe C. Nucleic Acids Res 2011; 39:4419-26. [PMID: 21252294 PMCID: PMC3105401 DOI: 10.1093/nar/gkr015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Previously, we developed the deoxycytosine analog Ç (C-spin) as a bi-functional spectroscopic probe for the study of nucleic acid structure and dynamics using electron paramagnetic resonance (EPR) and fluorescence spectroscopy. To understand the effect of Ç on nucleic acid structure, we undertook a detailed crystallographic analysis. A 1.7 Å resolution crystal structure of Ç within a decamer duplex A-form DNA confirmed that Ç forms a non-perturbing base pair with deoxyguanosine, as designed. In the context of double-stranded DNA Ç adopted a planar conformation. In contrast, a crystal structure of the free spin-labeled base ç displayed a ∼ 20° bend at the oxazine linkage. Density function theory calculations revealed that the bent and planar conformations are close in energy and exhibit the same frequency for bending. These results indicate a small degree of flexibility around the oxazine linkage, which may be a consequence of the antiaromaticity of a 16-π electron ring system. Within DNA, the amplitude of the bending motion is restricted, presumably due to base-stacking interactions. This structural analysis shows that the Ç forms a planar, structurally non-perturbing base pair with G indicating it can be used with high confidence in EPR- or fluorescence-based structural and dynamics studies.
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43
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Dallmann A, Dehmel L, Peters T, Mügge C, Griesinger C, Tuma J, Ernsting NP. 2-Aminopurine incorporation perturbs the dynamics and structure of DNA. Angew Chem Int Ed Engl 2010; 49:5989-92. [PMID: 20632340 DOI: 10.1002/anie.201001312] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- André Dallmann
- Humboldt Universität zu Berlin, Institut für Chemie, 12489 Berlin, Germany
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44
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Greco NJ, Sinkeldam RW, Tor Y. An emissive C analog distinguishes between G, 8-oxoG, and T. Org Lett 2010; 11:1115-8. [PMID: 19196162 DOI: 10.1021/ol802656n] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A minimally disruptive fluorescent dC analog provides a rapid and non-destructive method for in vitro detection of G, 8-oxoG, and T, the downstream transverse mutation product.
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Affiliation(s)
- Nicholas J Greco
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA
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45
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Dallmann A, Dehmel L, Peters T, Mügge C, Griesinger C, Tuma J, Ernsting N. Der Einbau von 2-Aminopurin beeinflusst die Dynamik und Struktur von DNA. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001312] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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46
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Preus S, Kilså K, Wilhelmsson LM, Albinsson B. Photophysical and structural properties of the fluorescent nucleobase analogues of the tricyclic cytosine (tC) family. Phys Chem Chem Phys 2010; 12:8881-92. [PMID: 20532361 DOI: 10.1039/c000625d] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Fundamental insight into the unique fluorescence and nucleobase-mimicking properties of the fluorescent nucleobase analogues of the tC family is not only vital in explaining the behaviour of these probes in nucleic acid environments, but will also be profitable in the development of new and improved fluorescent base analogues. Here, temperature-dependent fluorescence quantum yield measurements are used to successfully separate and quantify the temperature-dependent and temperature-independent non-radiative excited-state decay processes of the three nucleobase analogues tC, tC(O) and tC(nitro); all of which are derivatives of a phenothiazine or phenoxazine tricyclic framework. These results strongly suggest that the non-radiative decay process dominating the fast deactivation of tC(nitro) is an internal conversion of a different origin than the decay pathways of tC and tC(O). tC(nitro) is reported to be fluorescent only in less dipolar solvents at room temperature, which is explained by an increase in excited-state dipole moment along the main non-radiative decay pathway, a suggestion that applies in the photophysical discussion of large polycyclic nitroaromatics in general. New insight into the ground and excited-state potential energy surfaces of the isolated tC bases is obtained by means of high level DFT and TDDFT calculations. The S(0) potential energy surfaces of tC and tC(nitro) possess two global minima corresponding to geometries folded along the middle sulfur-nitrogen axis separated by an energy barrier of 0.05 eV as calculated at the B3LYP/6-311+G(2d,p) level. The ground-state potential energy surface of tC(O) is also predicted to be shallow along the bending coordinate but with an equilibrium geometry corresponding to the planar conformation of the tricyclic framework, which may explain some of the dissimilar properties of tC and tC(O) in various confined (biological) environments. The S(1) equilibrium geometries of all three base analogues are predicted to be planar. These results are discussed in the context of the tC bases positioned in double-stranded DNA scenarios.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen, Denmark.
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Abstract
The use of fluorescent nucleic acid base analogues is becoming increasingly important in the fields of biology, biochemistry and biophysical chemistry as well as in the field of DNA nanotechnology. The advantage of being able to incorporate a fluorescent probe molecule close to the site of examination in the nucleic acid-containing system of interest with merely a minimal perturbation to the natural structure makes fluorescent base analogues highly attractive. In recent years, there has been a growing interest in developing novel candidates in this group of fluorophores for utilization in various investigations. This review describes the different classes of fluorophores that can be used for studying nucleic acid-containing systems, with an emphasis on choosing the right kind of probe for the system under investigation. It describes the characteristics of the large group of base analogues that has an emission that is sensitive to the surrounding microenvironment and gives examples of investigations in which this group of molecules has been used so far. Furthermore, the characterization and use of fluorescent base analogues that are virtually insensitive to changes in their microenvironment are described in detail. This group of base analogues can be used in several fluorescence investigations of nucleic acids, especially in fluorescence anisotropy and fluorescence resonance energy transfer (FRET) measurements. Finally, the development and characterization of the first nucleic base analogue FRET pair, tC(O)-tC(nitro), and its possible future uses are discussed.
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Stengel G, Urban M, Purse BW, Kuchta RD. Incorporation of the fluorescent ribonucleotide analogue tCTP by T7 RNA polymerase. Anal Chem 2010; 82:1082-9. [PMID: 20067253 DOI: 10.1021/ac902456n] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fluorescent RNA is an important analytical tool in medical diagnostics, RNA cytochemistry, and RNA aptamer development. We have synthesized the fluorescent ribonucleotide analogue 1,3-diaza-2-oxophenothiazine-ribose-5'-triphosphate (tCTP) and tested it as substrate for T7 RNA polymerase in transcription reactions, a convenient route for generating RNA in vitro. When transcribing a guanine, T7 RNA polymerase incorporates tCTP with 2-fold higher catalytic efficiency than CTP and efficiently polymerizes additional NTPs onto the tC. Remarkably, T7 RNA polymerase does not incorporate tCTP with the same ambivalence opposite guanine and adenine with which DNA polymerases incorporate the analogous dtCTP. While several DNA polymerases discriminated against a d(tC-A) base pair only by factors <10, T7 RNA polymerase discriminates against tC-A base pair formation by factors of 40 and 300 when operating in the elongation and initiation mode, respectively. These catalytic properties make T7 RNA polymerase an ideal tool for synthesizing large fluorescent RNA, as we demonstrated by generating a approximately 800 nucleotide RNA in which every cytosine was replaced with tC.
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Affiliation(s)
- Gudrun Stengel
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 30309-0215, USA
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Sinkeldam RW, Greco NJ, Tor Y. Fluorescent analogs of biomolecular building blocks: design, properties, and applications. Chem Rev 2010; 110:2579-619. [PMID: 20205430 PMCID: PMC2868948 DOI: 10.1021/cr900301e] [Citation(s) in RCA: 665] [Impact Index Per Article: 47.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Renatus W. Sinkeldam
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
| | | | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
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Preus S, Börjesson K, Kilså K, Albinsson B, Wilhelmsson LM. Characterization of nucleobase analogue FRET acceptor tCnitro. J Phys Chem B 2010; 114:1050-6. [PMID: 20039634 DOI: 10.1021/jp909471b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fluorescent nucleobase analogues of the tricyclic cytosine (tC) family, tC and tC(O), possess high fluorescence quantum yields and single fluorescence lifetimes, even after incorporation into double-stranded DNA, which make these base analogues particularly useful as fluorescence resonance energy transfer (FRET) probes. Recently, we reported the first all-nucleobase FRET pair consisting of tC(O) as the donor and the novel tC(nitro) as the acceptor. The rigid and well-defined position of this FRET pair inside the DNA double helix, and consequently excellent control of the orientation factor in the FRET efficiency, are very promising features for future studies of nucleic acid structures. Here, we provide the necessary spectroscopic and photophysical characterization of tC(nitro) needed in order to utilize this probe as a FRET acceptor in nucleic acids. The lowest energy absorption band from 375 to 525 nm is shown to be the result of a single in-plane polarized electronic transition oriented approximately 27 degrees from the molecular long axis. This band overlaps the emission bands of both tC and tC(O), and the Forster characteristics of these donor-acceptor pairs are calculated for double-stranded DNA scenarios. In addition, the UV-vis absorption of tC(nitro) is monitored in a broad pH range and the neutral form is found to be totally predominant under physiological conditions with a pK(a) of 11.1. The structure and electronic spectrum of tC(nitro) is further characterized by density functional theory calculations.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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