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Boissieras J, Granzhan A. Potentiometric titrations to study ligand interactions with DNA i-motifs. Methods Enzymol 2023; 695:233-254. [PMID: 38521587 DOI: 10.1016/bs.mie.2023.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2024]
Abstract
i-Motifs are non-canonical secondary structures of DNA formed by mutual intercalation of hemi-protonated cytosine-cytosine base pairs, most typically in slightly acidic conditions (pH<7.0). These structures are well-studied in vitro and have recently been suggested to exist in cells. Despite nearly a decade of active research, the quest for small-molecule ligands that could selectively bind to and stabilize i-motifs continues, and no reference, bona fide i-motif ligand is currently available. This is, at least in part, due to the lack of robust methods to assess the interaction of ligands with i-motifs, since many techniques well-established for studies of other secondary structures (such as CD-, UV-, and FRET-melting) may generate artifacts when applied to i-motifs. Here, we describe an implementation of automated, potentiometric (pH) titrations as a robust isothermal method to assess the impact of ligands or cosolutes on thermodynamic stability of i-motifs. This approach is validated through the use of a cosolute previously known to stabilize i-motifs (PEG2000) and three small-molecule ligands that are able to stabilize, destabilize, or have no effect on the stability of i-motifs, respectively.
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Affiliation(s)
- Joseph Boissieras
- CMBC, CNRS UMR9187, INSERM U1196, Institut Curie, PSL Research University, Orsay, France; CMBC, CNRS UMR9187, INSERM U1196, Université Paris Saclay, Orsay, France
| | - Anton Granzhan
- CMBC, CNRS UMR9187, INSERM U1196, Institut Curie, PSL Research University, Orsay, France; CMBC, CNRS UMR9187, INSERM U1196, Université Paris Saclay, Orsay, France.
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Bansal A, Kaushik S, Kukreti S. Non-canonical DNA structures: Diversity and disease association. Front Genet 2022; 13:959258. [PMID: 36134025 PMCID: PMC9483843 DOI: 10.3389/fgene.2022.959258] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 07/25/2022] [Indexed: 11/18/2022] Open
Abstract
A complete understanding of DNA double-helical structure discovered by James Watson and Francis Crick in 1953, unveil the importance and significance of DNA. For the last seven decades, this has been a leading light in the course of the development of modern biology and biomedical science. Apart from the predominant B-form, experimental shreds of evidence have revealed the existence of a sequence-dependent structural diversity, unusual non-canonical structures like hairpin, cruciform, Z-DNA, multistranded structures such as DNA triplex, G-quadruplex, i-motif forms, etc. The diversity in the DNA structure depends on various factors such as base sequence, ions, superhelical stress, and ligands. In response to these various factors, the polymorphism of DNA regulates various genes via different processes like replication, transcription, translation, and recombination. However, altered levels of gene expression are associated with many human genetic diseases including neurological disorders and cancer. These non-B-DNA structures are expected to play a key role in determining genetic stability, DNA damage and repair etc. The present review is a modest attempt to summarize the available literature, illustrating the occurrence of non-canonical structures at the molecular level in response to the environment and interaction with ligands and proteins. This would provide an insight to understand the biological functions of these unusual DNA structures and their recognition as potential therapeutic targets for diverse genetic diseases.
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Affiliation(s)
- Aparna Bansal
- Nucleic Acid Research Lab, Department of Chemistry, University of Delhi, Delhi, India
- Department of Chemistry, Hansraj College, University of Delhi, Delhi, India
| | - Shikha Kaushik
- Nucleic Acid Research Lab, Department of Chemistry, University of Delhi, Delhi, India
- Department of Chemistry, Rajdhani College, University of Delhi, New Delhi, India
| | - Shrikant Kukreti
- Nucleic Acid Research Lab, Department of Chemistry, University of Delhi, Delhi, India
- *Correspondence: Shrikant Kukreti,
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3
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Stability and context of intercalated motifs (i-motifs) for biological applications. Biochimie 2022; 198:33-47. [PMID: 35259471 DOI: 10.1016/j.biochi.2022.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 02/21/2022] [Accepted: 03/03/2022] [Indexed: 11/24/2022]
Abstract
DNA is naturally dynamic and can self-assemble into alternative secondary structures including the intercalated motif (i-motif), a four-stranded structure formed in cytosine-rich DNA sequences. Until recently, i-motifs were thought to be unstable in physiological cellular environments. Studies demonstrating their existence in the human genome and role in gene regulation are now shining light on their biological relevance. Herein, we review the effects of epigenetic modifications on i-motif structure and stability, and biological factors that affect i-motif formation within cells. Furthermore, we highlight recent progress in targeting i-motifs with structure-specific ligands for biotechnology and therapeutic purposes.
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Gargallo R, Aviñó A, Eritja R, Jarosova P, Mazzini S, Scaglioni L, Taborsky P. Study of alkaloid berberine and its interaction with the human telomeric i-motif DNA structure. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 248:119185. [PMID: 33234477 DOI: 10.1016/j.saa.2020.119185] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/30/2020] [Accepted: 11/01/2020] [Indexed: 06/11/2023]
Abstract
The alkaloid berberine presents many biological activities related to its potential to bind DNA structures, such as duplex or G-quadruplex. Recently, it has been proposed that berberine may interact with i-motif structures formed from the folding of cytosine-rich sequences. In the present work, the interaction of this alkaloid with the i-motif formed by the human telomere cytosine-rich sequence, as well as with several positive and negative controls, has been studied. Molecular fluorescence and circular dichroism spectroscopies, as well as nuclear magnetic resonance spectrometry and competitive dialysis, have been used with this purpose. The results shown here reveal that the interaction of berberine with this i-motif is weak, mostly electrostatics in nature and takes place with bases not involved in C·C+ base pairs. Moreover, this ligand is not selective for i-motif structures, as binds equally to both, folded structure, and unfolded strand, without producing any stabilization of the i-motif. As a conclusion, the development of analytical methods based on the interaction of fluorescent ligands, such as berberine, with i-motif structures should consider the thermodynamic aspects related with the interaction, as well as the selectivity of the proposed ligands with different DNA structures, including unfolded strands.
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Affiliation(s)
- R Gargallo
- Dept. of Chemical Engineering and Analytical Chemistry, University of Barcelona, Marti i Franquès 1, E-08028 Barcelona, Spain.
| | - A Aviñó
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN, Jordi Girona 18-26, E-08034 Barcelona, Spain
| | - R Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN, Jordi Girona 18-26, E-08034 Barcelona, Spain
| | - P Jarosova
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - S Mazzini
- Department of Food, Environmental and Nutritional Sciences (DEFENS), Section of Chemical and Biomolecular Sciences, University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - L Scaglioni
- Department of Food, Environmental and Nutritional Sciences (DEFENS), Section of Chemical and Biomolecular Sciences, University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - P Taborsky
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
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5
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Brown SL, Kendrick S. The i-Motif as a Molecular Target: More Than a Complementary DNA Secondary Structure. Pharmaceuticals (Basel) 2021; 14:ph14020096. [PMID: 33513764 PMCID: PMC7911047 DOI: 10.3390/ph14020096] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/20/2021] [Accepted: 01/22/2021] [Indexed: 12/25/2022] Open
Abstract
Stretches of cytosine-rich DNA are capable of adopting a dynamic secondary structure, the i-motif. When within promoter regions, the i-motif has the potential to act as a molecular switch for controlling gene expression. However, i-motif structures in genomic areas of repetitive nucleotide sequences may play a role in facilitating or hindering expansion of these DNA elements. Despite research on the i-motif trailing behind the complementary G-quadruplex structure, recent discoveries including the identification of a specific i-motif antibody are pushing this field forward. This perspective reviews initial and current work characterizing the i-motif and providing insight into the biological function of this DNA structure, with a focus on how the i-motif can serve as a molecular target for developing new therapeutic approaches to modulate gene expression and extension of repetitive DNA.
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Abou Assi H, Garavís M, González C, Damha MJ. i-Motif DNA: structural features and significance to cell biology. Nucleic Acids Res 2019; 46:8038-8056. [PMID: 30124962 PMCID: PMC6144788 DOI: 10.1093/nar/gky735] [Citation(s) in RCA: 242] [Impact Index Per Article: 48.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 08/13/2018] [Indexed: 12/20/2022] Open
Abstract
The i-motif represents a paradigmatic example of the wide structural versatility of nucleic acids. In remarkable contrast to duplex DNA, i-motifs are four-stranded DNA structures held together by hemi- protonated and intercalated cytosine base pairs (C:C+). First observed 25 years ago, and considered by many as a mere structural oddity, interest in and discussion on the biological role of i-motifs have grown dramatically in recent years. In this review we focus on structural aspects of i-motif formation, the factors leading to its stabilization and recent studies describing the possible role of i-motifs in fundamental biological processes.
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Affiliation(s)
- Hala Abou Assi
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | - Miguel Garavís
- Instituto de Química Física 'Rocasolano', CSIC, C/Serrano 119, 28006 Madrid, Spain
| | - Carlos González
- Instituto de Química Física 'Rocasolano', CSIC, C/Serrano 119, 28006 Madrid, Spain
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
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Debnath M, Fatma K, Dash J. Chemical Regulation of DNA i‐Motifs for Nanobiotechnology and Therapeutics. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813288] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Manish Debnath
- School of Chemical SciencesIndian Association for the Cultivation of Science Jadavpur Kolkata- 700032 India
| | - Khushnood Fatma
- School of Chemical SciencesIndian Association for the Cultivation of Science Jadavpur Kolkata- 700032 India
| | - Jyotirmayee Dash
- School of Chemical SciencesIndian Association for the Cultivation of Science Jadavpur Kolkata- 700032 India
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Debnath M, Fatma K, Dash J. Chemical Regulation of DNA i-Motifs for Nanobiotechnology and Therapeutics. Angew Chem Int Ed Engl 2019; 58:2942-2957. [PMID: 30600876 DOI: 10.1002/anie.201813288] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/27/2018] [Indexed: 12/20/2022]
Abstract
DNA sequences rich in cytosine have the propensity, under acidic pH, to fold into four-stranded intercalated DNA structures called i-motifs. Recent studies have provided significant breakthroughs that demonstrate how chemists can manipulate these structures for nanobiotechnology and therapeutics. The first section of this Minireview discusses the development of advanced functional nanostructures by synthetic conjugation of i-motifs with organic scaffolds and metal nanoparticles and their role in therapeutics. The second section highlights the therapeutic targeting of i-motifs with chemical scaffolds and their significance in biology. For this, first we shed light on the long-lasting debate regarding the stability of i-motifs under physiological conditions. Next, we present a comparative analysis of recently reported small molecules for specifically targeting i-motifs over other abundant DNA structures and modulating their function in cellular systems. These advances provide new insights into i-motif-targeted regulation of gene expression, telomere maintenance, and therapeutic applications.
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Affiliation(s)
- Manish Debnath
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-, 700032, India
| | - Khushnood Fatma
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-, 700032, India
| | - Jyotirmayee Dash
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-, 700032, India
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Mir B, Solés X, González C, Escaja N. The effect of the neutral cytidine protonated analogue pseudoisocytidine on the stability of i-motif structures. Sci Rep 2017; 7:2772. [PMID: 28584239 PMCID: PMC5459817 DOI: 10.1038/s41598-017-02723-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 04/05/2017] [Indexed: 01/07/2023] Open
Abstract
Incorporation of pseudoisocytidine (psC), a neutral analogue of protonated cytidine, in i-motifs has been studied by spectroscopic methods. Our results show that neutral psC:C base pairs can stabilize i-motifs at neutral pH, but the stabilization only occurs when psC:C base pairs are located at the ends of intercalated C:C+ stacks. When psC occupies central positions, the resulting i-motifs are only observed at low pH and psC:C+ or psC:psC+ hemiprotonated base pairs are formed instead of their neutral analogs. Overall, our results suggest that positively charged base pairs are necessary to stabilize this non-canonical DNA structure.
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Affiliation(s)
- B Mir
- Inorganic and Organic Chemistry Department, Organic Chemistry Section, and IBUB, University of Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain
| | - X Solés
- Inorganic and Organic Chemistry Department, Organic Chemistry Section, and IBUB, University of Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain
| | - C González
- Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006, Madrid, Spain. .,BIOESTRAN, associated unit UB-CSIC, Spain.
| | - N Escaja
- Inorganic and Organic Chemistry Department, Organic Chemistry Section, and IBUB, University of Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain. .,BIOESTRAN, associated unit UB-CSIC, Spain.
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Aviñó A, Dellafiore M, Gargallo R, González C, Iribarren AM, Montserrat J, Eritja R. Stabilization of Telomeric I-Motif Structures by (2'S)-2'-Deoxy-2'-C-Methylcytidine Residues. Chembiochem 2017; 18:1123-1128. [PMID: 28407336 DOI: 10.1002/cbic.201700112] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Indexed: 01/12/2023]
Abstract
G-quadruplexes and i-motifs are tetraplex structures present in telomeres and the promoter regions of oncogenes. The possibility of producing nanodevices with pH-sensitive functions has triggered interest in modified oligonucleotides with improved structural properties. We synthesized C-rich oligonucleotides carrying conformationally restricted (2'S)-2'-deoxy-2'-C-methyl-cytidine units. The effect of this modified nucleoside on the stability of intramolecular i-motifs from the vertebrate telomere was investigated by UV, CD, and NMR spectroscopy. The replacement of selected positions of the C-core with C-modified residues induced the formation of stable intercalated tetraplexes at near-neutral pH. This study demonstrates the possibility of enhancing the stability of the i-motif by chemical modification.
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Affiliation(s)
- Anna Aviñó
- Institute for Advanced Chemistry of Catalonia (IQAC), Spanish Council for Scientific Research (CSIC), Jordi Girona 18-26, 08034, Barcelona, Spain.,Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)
| | - María Dellafiore
- INGEBI (CONICET), Vuelta de Obligado 2490-(1428), Buenos Aires, Argentina
| | - Raimundo Gargallo
- Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Martí i Franquès, 1-11, 08028, Barcelona, Spain.,BIOESTRAN, Associated Unit UB-CSIC
| | - Carlos González
- BIOESTRAN, Associated Unit UB-CSIC.,Institute of Physical Chemistry Rocasolano (IQFR), Spanish Council for Scientific Research (CSIC), Serrano 119, 28006, Madrid, Spain
| | - Adolfo M Iribarren
- CONICET. Laboratorio de Biotransformaciones, Universidad Nacional de Quilmes, Roque Saenz Peña 352 (1876) Bernal, Prov. de Buenos Aires, Argentina
| | - Javier Montserrat
- CONICET. Universidad Nacional de General Sarmiento, J. M. Gutiérrez 1150, 1613, Los Polvorines, Buenos Aires, Argentina
| | - Ramon Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC), Spanish Council for Scientific Research (CSIC), Jordi Girona 18-26, 08034, Barcelona, Spain.,Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)
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Alba JJ, Sadurní A, Gargallo R. Nucleic Acid i-Motif Structures in Analytical Chemistry. Crit Rev Anal Chem 2016; 46:443-54. [DOI: 10.1080/10408347.2016.1143347] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Joan Josep Alba
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
| | - Anna Sadurní
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
| | - Raimundo Gargallo
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
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12
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Dembska A. The analytical and biomedical potential of cytosine-rich oligonucleotides: A review. Anal Chim Acta 2016; 930:1-12. [PMID: 27265899 DOI: 10.1016/j.aca.2016.05.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 04/30/2016] [Accepted: 05/04/2016] [Indexed: 02/04/2023]
Abstract
Polycytosine DNA strands are often found among natural sequences, including the ends of telomeres, centromeres, and introns or in the regulatory regions of genes. A characteristic feature of oligonucleotides that are rich in cytosine (C-rich) is their ability to associate under acidic conditions to form a tetraplex i-motif consisting of two parallel stranded cytosine-hemiprotonated cytosine (C·C+) base-paired duplexes that are mutually intercalated in an antiparallel orientation. Nanotechnology has been exploiting the advantages of i-motif pH-dependent formation to fabricate nanomachines, nanoswitches, electrodes and intelligent nanosurfaces or nanomaterials. Although a few reviews regarding the structure, properties and applications of i-motifs have been published, this review focuses on recently developed biosensors (e.g., to detect pH, glucose or silver ions) and drug-delivery biomaterials. Furthermore, we have included examples of sensors based on parallel C-rich triplexes and silver nanoclusters (AgNCs) fabricated on cytosine-rich DNA strands. The potential diagnostic and therapeutic applications of this type of material are discussed.
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Affiliation(s)
- Anna Dembska
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznan, Poland.
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Assi HA, Harkness RW, Martin-Pintado N, Wilds CJ, Campos-Olivas R, Mittermaier AK, González C, Damha MJ. Stabilization of i-motif structures by 2'-β-fluorination of DNA. Nucleic Acids Res 2016; 44:4998-5009. [PMID: 27166371 PMCID: PMC4914123 DOI: 10.1093/nar/gkw402] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 05/02/2016] [Indexed: 01/12/2023] Open
Abstract
i-Motifs are four-stranded DNA structures consisting of two parallel DNA duplexes held together by hemi-protonated and intercalated cytosine base pairs (C:CH+). They have attracted considerable research interest for their potential role in gene regulation and their use as pH responsive switches and building blocks in macromolecular assemblies. At neutral and basic pH values, the cytosine bases deprotonate and the structure unfolds into single strands. To avoid this limitation and expand the range of environmental conditions supporting i-motif folding, we replaced the sugar in DNA by 2-deoxy-2-fluoroarabinose. We demonstrate that such a modification significantly stabilizes i-motif formation over a wide pH range, including pH 7. Nuclear magnetic resonance experiments reveal that 2-deoxy-2-fluoroarabinose adopts a C2′-endo conformation, instead of the C3′-endo conformation usually found in unmodified i-motifs. Nevertheless, this substitution does not alter the overall i-motif structure. This conformational change, together with the changes in charge distribution in the sugar caused by the electronegative fluorine atoms, leads to a number of favorable sequential and inter-strand electrostatic interactions. The availability of folded i-motifs at neutral pH will aid investigations into the biological function of i-motifs in vitro, and will expand i-motif applications in nanotechnology.
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Affiliation(s)
- Hala Abou Assi
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | - Robert W Harkness
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | | | - Christopher J Wilds
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada Department of Chemistry and Biochemistry, Concordia University, Montreal, QC H4B 1R6, Canada
| | | | | | - Carlos González
- Instituto de Química Física 'Rocasolano', CSIC, 28006 Madrid, Spain
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
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