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Bednarz A, Rosendal RT, Lund LM, Birkedal V. Probing G-quadruplex-ligand binding using DNA intrinsic fluorescence. Biochimie 2024:S0300-9084(24)00145-7. [PMID: 38936685 DOI: 10.1016/j.biochi.2024.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 06/24/2024] [Accepted: 06/24/2024] [Indexed: 06/29/2024]
Abstract
G-quadruplexes (G4s) are helical four-stranded nucleic acid structures that can form in guanine-rich sequences, which are mostly found in functional cellular regions, such as telomeres, promoters, and DNA replication origins. Great efforts are being made to target these structures towards the development of specific small molecule G4 binders for novel anti-cancer, neurological, and viral therapies. Here, we introduce an optical assay based on quenching of the intrinsic fluorescence of DNA G-quadruplexes for assessing and comparing the G4 binding affinity of various small molecule ligands in solutions. We show that the approach allows direct quantification of ligand binding to distinctive G4 topologies. We believe that this method will facilitate quick and reliable evaluation of small molecule G4 ligands and support their development.
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Affiliation(s)
- Aleksandra Bednarz
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Denmark; Department of Chemistry, Aarhus University, Denmark
| | - Rebecca Torp Rosendal
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Denmark; Department of Chemistry, Aarhus University, Denmark
| | - Line Mørkholt Lund
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Denmark; Department of Chemistry, Aarhus University, Denmark
| | - Victoria Birkedal
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Denmark; Department of Chemistry, Aarhus University, Denmark.
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Markovitsi D. On the Use of the Intrinsic DNA Fluorescence for Monitoring Its Damage: A Contribution from Fundamental Studies. ACS OMEGA 2024; 9:26826-26837. [PMID: 38947837 PMCID: PMC11209687 DOI: 10.1021/acsomega.4c02256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 05/02/2024] [Accepted: 05/08/2024] [Indexed: 07/02/2024]
Abstract
The assessment of DNA damage by means of appropriate fluorescent probes is widely spread. In the specific case of UV-induced damage, it has been suggested to use the emission of dimeric photoproducts as an internal indicator for the efficacy of spermicidal lamps. However, in the light of fundamental studies on the UV-induced processes, outlined in this review, this is not straightforward. It is by now well established that, in addition to photodimers formed via an electronic excited state, photoionization also takes place with comparable or higher quantum yields, depending on the irradiation wavelength. Among the multitude of final lesions, some have been fully characterized, but others remain unknown; some of them may emit, while others go undetected upon monitoring fluorescence, the result being strongly dependent on both the irradiation and the excitation wavelength. In contrast, the fluorescence of undamaged nucleobases associated with emission from ππ* states, localized or excitonic, appearing at wavelengths shorter than 330 nm is worthy of being explored to this end. Despite its low quantum yield, it is readily detected nowadays. Its intensity decreases due to the disappearance of the reacting nucleobases and the loss of exciton coherence provoked by the presence of lesions, independently of their type. Thus, it could potentially provide valuable information about the DNA damage induced, not only by UV radiation but also by other sanitizing or therapeutic agents.
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Affiliation(s)
- Dimitra Markovitsi
- Université Paris-Saclay, CNRS,
Institut de Chimie Physique, UMR8000, 91405 Orsay, France
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3
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Markovitsi D. Processes triggered in guanine quadruplexes by direct absorption of UV radiation: From fundamental studies toward optoelectronic biosensors. Photochem Photobiol 2024; 100:262-274. [PMID: 37365765 DOI: 10.1111/php.13826] [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] [Received: 05/03/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/28/2023]
Abstract
Guanine quadruplexes (GQs) are four-stranded DNA/RNA structures exhibiting an important polymorphism. During the past two decades, their study by time-resolved spectroscopy, from femtoseconds to milliseconds, associated to computational methods, shed light on the primary processes occurring when they absorb UV radiation. Quite recently, their utilization in label-free and dye-free biosensors was explored by a few groups. In view of such developments, this review discusses the outcomes of the fundamental studies that could contribute to the design of future optoelectronic biosensors using fluorescence or charge carriers stemming directly from GQs, without mediation of other molecules, as it is the currently the case. It explains how the excited state relaxation influences both the fluorescence intensity and the efficiency of low-energy photoionization, occurring via a complex mechanism. The corresponding quantum yields, determined with excitation at 266/267 nm, fall in the range of (3.0-9.5) × 10-4 and (3.2-9.2) × 10-3 , respectively. These values, significantly higher than the corresponding values found for duplexes, depend strongly on certain structural factors (molecularity, metal cations, peripheral bases, number of tetrads …) which intervene in the relaxation process. Accordingly, these features can be tuned to optimize the desired signal.
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Affiliation(s)
- Dimitra Markovitsi
- CNRS, Institut de Chimie Physique, UMR8000, Université Paris-Saclay, Orsay, France
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Tevonyan LL, Beniaminov AD, Kaluzhny DN. Quenching of G4-DNA intrinsic fluorescence by ligands. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2024; 53:47-56. [PMID: 38217705 DOI: 10.1007/s00249-023-01696-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 11/10/2023] [Accepted: 12/11/2023] [Indexed: 01/15/2024]
Abstract
G-quadruplex (G4) structures formed by the guanine-rich DNA regions exhibit several distinctive optical properties, including UV absorption and circular dichroism spectra. Some G4 DNA possess intrinsic UV fluorescence whose origin is not completely clear to date. In this work, we study the effect of TMPyP4 and Methylene Blue on the intrinsic fluorescence of the dimeric G4 DNA structure formed by two d(G3T)4 sequences. We demonstrate that binding of the ligands results in quenching of the intrinsic fluorescence, although the conformation of the G4 DNA and its dimeric structure remain preserved. The binding sites of the ligands were suggested by the photoinduced oxidation of guanines and analysis of binding isoterms. We discuss how DNA-ligand complexes can affect the intrinsic fluorescence of G4 DNA.
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Affiliation(s)
- Liana L Tevonyan
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991, Moscow, Russia
| | - Artemy D Beniaminov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991, Moscow, Russia
| | - Dmitry N Kaluzhny
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991, Moscow, Russia.
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Johnson RE, Murray MT, Roby DJ, Bycraft LJ, Churcher ZR, Yadav S, Johnson PE, Wetmore SD, Manderville RA. Unlocking Pb 2+ Sensing Potential in a DNA G-Quadruplex via Loop Modification with Fluorescent Chalcone Surrogates. ACS Sens 2023; 8:4756-4764. [PMID: 38063049 DOI: 10.1021/acssensors.3c01866] [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: 12/23/2023]
Abstract
The ability of guanine (G)-rich DNA to bind toxic lead (Pb2+) ions within a G-quadruplex (GQ) motif is a leading DNA biosensor strategy. A major analytical hurdle for GQ detection of Pb2+ is competitive GQ templating by potassium (K+) ions. We employ the on-strand DNA synthesis of internal fluorescent chalcone surrogates within the 15-mer thrombin binding aptamer (TBA15) to address this challenge. Replacement of thymidine at the 3-position (T3) within TBA15 with an indole-4-hydroxy-indanone (Ind4HI) chalcone strongly decreases K+-GQ stability while enhancing Pb2+-GQ stability to increase Pb2+ binding specificity. The new T3-Ind4HI probe exhibits a 15-fold increase in fluorescence intensity upon binding of Pb2+ by the modified TBA15 and can detect 6.4 nM Pb2+ in the presence of 10 mM K+. Thus, replacement of the T3 residue of TBA15 with the new Ind4HI probe modulates metal ion affinity by native TBA15 to solve the analytical challenge posed by K+ in real water samples for detecting Pb2+ to meet regulatory guidelines by using a GQ biosensor.
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Affiliation(s)
- Ryan E Johnson
- Departments of Chemistry and Toxicology, University of Guelph, Guelph N1G 2W1, Ontario, Canada
| | - Makay T Murray
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge T1K 3M4, Alberta, Canada
| | - Dylan J Roby
- Departments of Chemistry and Toxicology, University of Guelph, Guelph N1G 2W1, Ontario, Canada
| | - Lucas J Bycraft
- Departments of Chemistry and Toxicology, University of Guelph, Guelph N1G 2W1, Ontario, Canada
| | - Zachary R Churcher
- Department of Chemistry, York University, Toronto M3J 1P3, Ontario, Canada
| | - Saanya Yadav
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge T1K 3M4, Alberta, Canada
| | - Philip E Johnson
- Department of Chemistry, York University, Toronto M3J 1P3, Ontario, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge T1K 3M4, Alberta, Canada
| | - Richard A Manderville
- Departments of Chemistry and Toxicology, University of Guelph, Guelph N1G 2W1, Ontario, Canada
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Balanikas E, Gustavsson T, Markovitsi D. Fluorescence of Bimolecular Guanine Quadruplexes: From Femtoseconds to Nanoseconds. J Phys Chem B 2023; 127:172-179. [PMID: 36577031 DOI: 10.1021/acs.jpcb.2c07647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The paper deals with the fluorescence of guanine quadruplexes (G4) formed by association of two DNA strands d(GGGGTTTTGGGG) in the presence of K+ cations, noted as OXY/K+ in reference to the protozoon Oxytricha nova, whose telomere contains TTTTGGGG repeats. They were studied by steady-state and time-resolved techniques, time-correlated single photon counting, and fluorescence upconversion. The maximum of the OXY/K+ fluorescence spectrum is located at 334 nm, and the quantum yield is 5.8 × 10-4. About 75% of the photons are emitted before 100 ps and stem from ππ* states, possibly with a small contribution of charge transfer. Time-resolved fluorescence anisotropy measurements indicate that ultrafast (<330 fs) excitation transfer, due to internal conversion among exciton states, is more efficient in OXY/K+ compared to previously studied G4 structures. This is attributed to the arrangement of the peripheral thymines in two diagonal loops with restricted mobility, facilitating the interaction among them and with guanines. Thymines should also be responsible for a weak intensity excimer/exciplex emission band, peaking at 445 nm. Finally, the longest living fluorescence component (∼2.1 ns) is observed at the blue side of the spectrum. So far, high-energy long-lived emitting states had been reported only for double-stranded structures but not for G4.
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Affiliation(s)
| | - Thomas Gustavsson
- CEA, CNRS, LIDYL, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
| | - Dimitra Markovitsi
- CEA, CNRS, LIDYL, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.,CNRS, Institut de Chimie Physique, UMR8000, Université Paris-Saclay, 91405 Orsay, France
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Lu C, Lopez A, Zheng J, Liu J. Using the Intrinsic Fluorescence of DNA to Characterize Aptamer Binding. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27227809. [PMID: 36431910 PMCID: PMC9692703 DOI: 10.3390/molecules27227809] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/08/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022]
Abstract
The reliable, readily accessible and label-free measurement of aptamer binding remains a challenge in the field. Recent reports have shown large changes in the intrinsic fluorescence of DNA upon the formation of G-quadruplex and i-motif structures. In this work, we examined whether DNA intrinsic fluorescence can be used for studying aptamer binding. First, DNA hybridization resulted in a drop in the fluorescence, which was observed for A30/T30 and a 24-mer random DNA sequence. Next, a series of DNA aptamers were studied. Cortisol and Hg2+ induced fluorescence increases for their respective aptamers. For the cortisol aptamer, the length of the terminal stem needs to be short to produce a fluorescence change. However, caffeine and adenosine failed to produce a fluorescence change, regardless of the stem length. Overall, using the intrinsic fluorescence of DNA may be a reliable and accessible method to study a limited number of aptamers that can produce fluorescence changes.
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Affiliation(s)
- Chang Lu
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Anand Lopez
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Jinkai Zheng
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
- Correspondence:
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