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Dziuba D. Environmentally sensitive fluorescent nucleoside analogues as probes for nucleic acid - protein interactions: molecular design and biosensing applications. Methods Appl Fluoresc 2022; 10. [PMID: 35738250 DOI: 10.1088/2050-6120/ac7bd8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 06/23/2022] [Indexed: 11/12/2022]
Abstract
Fluorescent nucleoside analogues (FNAs) are indispensable in studying the interactions of nucleic acids with nucleic acid-binding proteins. By replacing one of the poorly emissive natural nucleosides, FNAs enable real-time optical monitoring of the binding interactions in solutions, under physiologically relevant conditions, with high sensitivity. Besides that, FNAs are widely used to probe conformational dynamics of biomolecular complexes using time-resolved fluorescence methods. Because of that, FNAs are tools of high utility for fundamental biological research, with potential applications in molecular diagnostics and drug discovery. Here I review the structural and physical factors that can be used for the conversion of the molecular binding events into a detectable fluorescence output. Typical environmentally sensitive FNAs, their properties and applications, and future challenges in the field are discussed.
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Affiliation(s)
- Dmytro Dziuba
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, 74 Route du Rhin, Illkirch-Graffenstaden, Grand Est, 67401, FRANCE
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2
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Dziuba D, Didier P, Ciaco S, Barth A, Seidel CAM, Mély Y. Fundamental photophysics of isomorphic and expanded fluorescent nucleoside analogues. Chem Soc Rev 2021; 50:7062-7107. [PMID: 33956014 DOI: 10.1039/d1cs00194a] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fluorescent nucleoside analogues (FNAs) are structurally diverse mimics of the natural essentially non-fluorescent nucleosides which have found numerous applications in probing the structure and dynamics of nucleic acids as well as their interactions with various biomolecules. In order to minimize disturbance in the labelled nucleic acid sequences, the FNA chromophoric groups should resemble the natural nucleobases in size and hydrogen-bonding patterns. Isomorphic and expanded FNAs are the two groups that best meet the criteria of non-perturbing fluorescent labels for DNA and RNA. Significant progress has been made over the past decades in understanding the fundamental photophysics that governs the spectroscopic and environmentally sensitive properties of these FNAs. Herein, we review recent advances in the spectroscopic and computational studies of selected isomorphic and expanded FNAs. We also show how this information can be used as a rational basis to design new FNAs, select appropriate sequences for optimal spectroscopic response and interpret fluorescence data in FNA applications.
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Affiliation(s)
- Dmytro Dziuba
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Pascal Didier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Stefano Ciaco
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France. and Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via Aldo Moro 2, 53100 Siena, Italy
| | - Anders Barth
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Claus A M Seidel
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Yves Mély
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
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3
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Mismatch Recognition by Saccharomyces cerevisiae Msh2-Msh6: Role of Structure and Dynamics. Int J Mol Sci 2019; 20:ijms20174271. [PMID: 31480444 PMCID: PMC6747400 DOI: 10.3390/ijms20174271] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 08/27/2019] [Accepted: 08/27/2019] [Indexed: 12/12/2022] Open
Abstract
The mismatch repair (MMR) pathway maintains genome integrity by correcting errors such as mismatched base pairs formed during DNA replication. In MMR, Msh2–Msh6, a heterodimeric protein, targets single base mismatches and small insertion/deletion loops for repair. By incorporating the fluorescent nucleoside base analog 6-methylisoxanthopterin (6-MI) at or adjacent to a mismatch site to probe the structural and dynamic elements of the mismatch, we address how Msh2–Msh6 recognizes these mismatches for repair within the context of matched DNA. Fluorescence quantum yield and rotational correlation time measurements indicate that local base dynamics linearly correlate with Saccharomyces cerevisiae Msh2–Msh6 binding affinity where the protein exhibits a higher affinity (KD ≤ 25 nM) for mismatches that have a significant amount of dynamic motion. Energy transfer measurements measuring global DNA bending find that mismatches that are both well and poorly recognized by Msh2–Msh6 experience the same amount of protein-induced bending. Finally, base-specific dynamics coupled with protein-induced blue shifts in peak emission strongly support the crystallographic model of directional binding, in which Phe 432 of Msh6 intercalates 3′ of the mismatch. These results imply an important role for local base dynamics in the initial recognition step of MMR.
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4
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Wang W, Sheng X, Zhang S, Huang F, Sun C, Liu J, Chen D. Theoretical insights into the structural and fluorescence properties of DNA containing fluorescent nucleobases. Phys Chem Chem Phys 2018; 20:16641-16649. [DOI: 10.1039/c8cp02295j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The structural and fluorescence properties of DNA containing fluorescent nucleobases are explored in detail. In particular, the effect of stacking with different neighboring bases on fluorescence properties is elucidated.
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Affiliation(s)
- Wenjuan Wang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Xiehuang Sheng
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Shaolong Zhang
- College of Physics and Electronics
- Shandong Normal University
- Jinan 250014
- P. R. China
| | - Fang Huang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Chuanzhi Sun
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Jianbiao Liu
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Dezhan Chen
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
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5
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Fluorescent nucleobases as tools for studying DNA and RNA. Nat Chem 2017; 9:1043-1055. [PMID: 29064490 DOI: 10.1038/nchem.2859] [Citation(s) in RCA: 208] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 07/11/2017] [Indexed: 02/07/2023]
Abstract
Understanding the diversity of dynamic structures and functions of DNA and RNA in biology requires tools that can selectively and intimately probe these biomolecules. Synthetic fluorescent nucleobases that can be incorporated into nucleic acids alongside their natural counterparts have emerged as a powerful class of molecular reporters of location and environment. They are enabling new basic insights into DNA and RNA, and are facilitating a broad range of new technologies with chemical, biological and biomedical applications. In this Review, we will present a brief history of the development of fluorescent nucleobases and explore their utility as tools for addressing questions in biophysics, biochemistry and biology of nucleic acids. We provide chemical insights into the two main classes of these compounds: canonical and non-canonical nucleobases. A point-by-point discussion of the advantages and disadvantages of both types of fluorescent nucleobases is made, along with a perspective into the future challenges and outlook for this burgeoning field.
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Kilin V, Gavvala K, Barthes NPF, Michel BY, Shin D, Boudier C, Mauffret O, Yashchuk V, Mousli M, Ruff M, Granger F, Eiler S, Bronner C, Tor Y, Burger A, Mély Y. Dynamics of Methylated Cytosine Flipping by UHRF1. J Am Chem Soc 2017; 139:2520-2528. [PMID: 28112929 PMCID: PMC5335914 DOI: 10.1021/jacs.7b00154] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
DNA methylation patterns, which are critical for gene expression, are replicated by DNA methyltransferase 1 (DNMT1) and ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) proteins. This replication is initiated by the recognition of hemimethylated CpG sites and further flipping of methylated cytosines (mC) by the Set and Ring Associated (SRA) domain of UHRF1. Although crystallography has shed light on the mechanism of mC flipping by SRA, tools are required to monitor in real time how SRA reads DNA and flips the modified nucleobase. To accomplish this aim, we have utilized two distinct fluorescent nucleobase surrogates, 2-thienyl-3-hydroxychromone nucleoside (3HCnt) and thienoguanosine (thG), incorporated at different positions into hemimethylated (HM) and nonmethylated (NM) DNA duplexes. Large fluorescence changes were associated with mC flipping in HM duplexes, showing the outstanding sensitivity of both nucleobase surrogates to the small structural changes accompanying base flipping. Importantly, the nucleobase surrogates marginally affected the structure of the duplex and its affinity for SRA at positions where they were responsive to base flipping, illustrating their promise as nonperturbing probes for monitoring such events. Stopped-flow studies using these two distinct tools revealed the fast kinetics of SRA binding and sliding to NM duplexes, consistent with its reader role. In contrast, the kinetics of mC flipping was found to be much slower in HM duplexes, substantially increasing the lifetime of CpG-bound UHRF1, and thus the probability of recruiting DNMT1 to faithfully duplicate the DNA methylation profile. The fluorescence-based approach using these two different fluorescent nucleoside surrogates advances the mechanistic understanding of the UHRF1/DNMT1 tandem and the development of assays for the identification of base flipping inhibitors.
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Affiliation(s)
- Vasyl Kilin
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Universitéde Strasbourg, Facultéde pharmacie, 74 Route du Rhin, 67401 Illkirch, France
| | - Krishna Gavvala
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Universitéde Strasbourg, Facultéde pharmacie, 74 Route du Rhin, 67401 Illkirch, France
| | - Nicolas P. F. Barthes
- Institut de Chimie de Nice, UMR 7272 CNRS, UniversitéCôte d’Azur, Parc Valrose, 06108 Nice Cedex 2, France
| | - Benoît Y. Michel
- Institut de Chimie de Nice, UMR 7272 CNRS, UniversitéCôte d’Azur, Parc Valrose, 06108 Nice Cedex 2, France
| | - Dongwon Shin
- TriLink BioTechnologies, LLC., San Diego, California 92121, United States
| | - Christian Boudier
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Universitéde Strasbourg, Facultéde pharmacie, 74 Route du Rhin, 67401 Illkirch, France
| | - Olivier Mauffret
- LBPA, UMR 8113 CNRS, ENS Paris-Saclay, Université Paris Saclay, 94235 Cachan Cedex, France
| | - Valeriy Yashchuk
- Department of Physics, Kiev National Taras Shevchenko University, Kiev 01601, Ukraine
| | - Marc Mousli
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Universitéde Strasbourg, Facultéde pharmacie, 74 Route du Rhin, 67401 Illkirch, France
| | - Marc Ruff
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964 CNRS UMR 7104, Université de Strasbourg, Illkirch 67000, France
| | - Florence Granger
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964 CNRS UMR 7104, Université de Strasbourg, Illkirch 67000, France
| | - Sylvia Eiler
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964 CNRS UMR 7104, Université de Strasbourg, Illkirch 67000, France
| | - Christian Bronner
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964 CNRS UMR 7104, Université de Strasbourg, Illkirch 67000, France
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358, United States
| | - Alain Burger
- Institut de Chimie de Nice, UMR 7272 CNRS, UniversitéCôte d’Azur, Parc Valrose, 06108 Nice Cedex 2, France
| | - Yves Mély
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Universitéde Strasbourg, Facultéde pharmacie, 74 Route du Rhin, 67401 Illkirch, France
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7
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Moreno A, Knee JL, Mukerji I. Photophysical Characterization of Enhanced 6-Methylisoxanthopterin Fluorescence in Duplex DNA. J Phys Chem B 2016; 120:12232-12248. [PMID: 27934220 DOI: 10.1021/acs.jpcb.6b07369] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The structure and dynamic motions of bases in DNA duplexes and other constructs are important for understanding mechanisms of selectivity and recognition of DNA-binding proteins. The fluorescent guanine analogue, 6-methylisoxanthopterin 6-MI, is well suited to this purpose as it exhibits an unexpected 3- to 4-fold increase in relative quantum yield upon duplex formation when incorporated into the following sequences: ATFAA, AAFTA, or ATFTA (where F represents 6-MI). To better understand some of the factors leading to the 6-MI fluorescence increase upon duplex formation, we characterized the effect of local sequence and structural perturbations on 6-MI photophysics through temperature melts, quantum yield measurements, fluorescence quenching assays, and fluorescence lifetime measurements. By examining 21 sequences we have determined that the duplex-enhanced fluorescence (DEF) depends on the composition of bases adjacent to 6-MI and the presence of adenines at locations n ± 2 from the probe. Investigation of duplex stability and local solvent accessibility measurements support a model in which the DEF arises from a constrained geometry of 6-MI in the duplex, which remains H-bonded to cytosine, stacked with adjacent bases and inaccessible to quenchers. Perturbation of DNA structure through the introduction of an unpaired base 3' to 6-MI or a mismatched basepair increases 6-MI dynamic motion leading to fluorescence quenching and a reduction in quantum yield. Molecular dynamics simulations suggest the enhanced fluorescence results from a greater degree of twist at the X-F step relative to the quenched duplexes examined. These results point to a model where adenine residues located at n ± 2 from 6-MI induce a structural geometry with greater twist in the duplex that hinders local motion reducing dynamic quenching and producing an increase in 6-MI fluorescence.
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Affiliation(s)
- Andrew Moreno
- Departments of Chemistry and ‡Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University , 52 Lawn Ave, Middletown, Connecticut 06459, United States
| | - J L Knee
- Departments of Chemistry and ‡Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University , 52 Lawn Ave, Middletown, Connecticut 06459, United States
| | - Ishita Mukerji
- Departments of Chemistry and ‡Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University , 52 Lawn Ave, Middletown, Connecticut 06459, United States
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8
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Gogichaishvili S, Johnson J, Gvarjaladze D, Lomidze L, Kankia B. Isothermal amplification of DNA using quadruplex primers with fluorescent pteridine base analogue 3-methyl isoxanthopterin. Biopolymers 2016; 101:583-90. [PMID: 24122726 DOI: 10.1002/bip.22421] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 09/24/2013] [Indexed: 11/08/2022]
Abstract
We previously developed a method, known as quadruplex priming amplification (QPA), which greatly simplifies DNA amplification and quantification assays. QPA employs specific primers based on GGGTGGGTGGGTGGG (G3T) sequence, which upon polymerase elongation spontaneously dissociates from the target and folds into a stable quadruplex. Fluorescent nucleotide analogs, when incorporated into these primers, emit light upon quadruplex formation and permit simple, specific, and sensitive quantification without the attachment of probe molecules. Here, we studied optical [fluorescence and circular dichroism (CD)] and thermodynamic properties of the G3T sequence and variants incorporating 3-methylisoxanthopterin (3MI), a highly fluorescent nucleotide analog suitable for QPA. CD studies demonstrate that the incorporation of 3MI does not change the overall tertiary structure of G3T; however, thermal unfolding experiments revealed that it significantly destabilizes the quadruplex. Enzymatic studies revealed that Taq and Bst are practically unable to incorporate any nucleotides opposite to template 3MI. Based on this knowledge, we designed QPA assays with truncated targets that demonstrate efficient amplification around 55°C. Overall, these studies suggest that 3MI-based QPA is a useful assay for DNA amplification and detection.
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Affiliation(s)
- Shota Gogichaishvili
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210; Andronikashvili Institute of Physics, Tbilisi, 0177, Republic of Georgia
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9
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Partskhaladze T, Taylor A, Lomidze L, Gvarjaladze D, Kankia B. Exponential quadruplex priming amplification for DNA-based isothermal diagnostics. Biopolymers 2016; 103:88-95. [PMID: 25269836 DOI: 10.1002/bip.22557] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Revised: 07/27/2014] [Accepted: 08/14/2014] [Indexed: 01/14/2023]
Abstract
Polymerase chain reaction (PCR) is a method of choice for molecular diagnostics. However, PCR relies on thermal cycling, which is not compatible with the goals of point-of-care diagnostics. A simple strategy to turn PCR into an isothermal method would be to use specific primers, which upon polymerase elongation can self-dissociate from the primer-binding sites. We recently demonstrated that a monomolecular DNA quadruplex, GGGTGGGTGGGTGGG, meets these requirements, which led to the development of the linear versions of quadruplex priming amplification (QPA). Here we demonstrate exponential version of isothermal QPA, which allows an unprecedented 10(10)-fold amplification of DNA signal in less than 40 min.
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Affiliation(s)
- Tamar Partskhaladze
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210
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10
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Preclinical profile of BI 224436, a novel HIV-1 non-catalytic-site integrase inhibitor. Antimicrob Agents Chemother 2014; 58:3233-44. [PMID: 24663024 DOI: 10.1128/aac.02719-13] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3'-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC50s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 μM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC95 values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.
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11
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Costa JA, Leal-Pinto E, Henderson SC, Zabel T, Hawkins ME, Hanss B. Use of a Pteridine Moiety to Track DNA Uptake in Cells. Pteridines 2014; 23:81-89. [PMID: 24465092 DOI: 10.1515/pteridines.2012.23.1.81] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Fluorescence labeled oligonucleotides have a long history of being used to monitor nucleic acid transport and uptake. However, it is not known if the fluorescent moiety itself physically limits the number of pathways that can be used by the cell due to steric, hydrophobic, or other chemical characteristics. Here, we report a method for comparing the uptake kinetics of oligonucleotides labeled either with the fluorescent pteridine, 3-methyl-8-(2-deoxy-β-D-ribofuranosyl) isoxanthopterin (3MI), or the common fluorophore 5-carboxyfluorescein (5-FAM). We use a multiphoton microscopic technique to monitor nucleic acid uptake LLC-PK1, a pig renal tubular cell line that is known to have multiple uptake pathways. We find that the two fluorophores enter the cells at different rates, suggesting that choice of fluorescent moiety influences the uptake pathway used by a cell. Finally, we reconstituted an LLC-PK1 membrane channel that is selective for nucleic acids in planar lipid bilayers, and tested the ability of the labeled nucleic acids to permeate the channel. We find that 3MI, and not 5-FAM labeled oligonucleotides can traverse the plasma membrane through the channel. These results have implications for future studies aimed at delivering pteridine moieties to cells and for tracking nucleic acid transport into tissues.
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Affiliation(s)
- Justin A Costa
- Division of Nephrology, Department of Medicine, Mt. Sinai School of Medicine, New York, NY
| | - Edgar Leal-Pinto
- Department of Physiology and Biophysics, Virginia Commonwealth University Medical Center, Richmond, VA
| | - Scott C Henderson
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, Richmond, VA
| | | | - Mary E Hawkins
- Laboratory of Receptor Biology and Gene Expression, NCI/NIH, Bethesda, MD
| | - Basil Hanss
- Division of Nephrology, Department of Medicine, Mt. Sinai School of Medicine, New York, NY
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12
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Tanpure AA, Pawar MG, Srivatsan SG. Fluorescent Nucleoside Analogs: Probes for Investigating Nucleic Acid Structure and Function. Isr J Chem 2013. [DOI: 10.1002/ijch.201300010] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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13
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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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14
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Moreno A, Knee J, Mukerji I. Applying 6-methylisoxanthopterin-enhanced fluorescence to examine protein-DNA interactions in the picomolar range. Biochemistry 2012; 51:6847-59. [PMID: 22849374 DOI: 10.1021/bi300466d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Incorporation of fluorescent nucleoside analogues into duplex DNA usually leads to a reduction in quantum yield, which significantly limits their potential use and application. We have identified two pentamer DNA sequences containing 6-methylisoxanthopterin (6-MI) (ATFAA and AAFTA, where F is 6-MI) that exhibit significant enhancement of fluorescence upon formation of duplex DNA with quantum yields close to that of monomeric 6-MI. The enhanced fluorescence dramatically increases the utility and sensitivity of the probe and is used to study protein-DNA interactions of nanomolar specificity in this work. The increased sensitivity of 6-MI allows anisotropy binding measurements to be performed at DNA concentrations of 1 nM and fluorescence intensity measurements at 50 pM DNA. The ATFAA sequence was incorporated into DNA constructs to measure the binding affinity of four different protein-DNA interactions that exhibit sequence-specific and non-sequence-specific recognition. In all cases, the K(d) values obtained were consistent with previously reported values measured by other methods. Time-resolved and steady-state fluorescence measurements demonstrate that 6-MI fluorescence is very sensitive to local distortion and reports on different degrees of protein-induced perturbations with single-base resolution, where the largest changes occur at the site of protein binding.
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Affiliation(s)
- Andrew Moreno
- Departments of Chemistry and Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA
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15
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Anisenko A, Agapkina J, Zatsepin T, Yanvarev D, Gottikh M. A new fluorometric assay for the study of DNA-binding and 3'-processing activities of retroviral integrases and its use for screening of HIV-1 integrase inhibitors. Biochimie 2012; 94:2382-90. [PMID: 22728110 DOI: 10.1016/j.biochi.2012.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 06/07/2012] [Indexed: 11/24/2022]
Abstract
Fluorometry using a substrate DNA labeled with a single fluorophore (6-carboxyfluorescein) at the 3'-end of the processed strand was shown to be a useful tool for monitoring DNA-binding and 3'-processing activities of HIV-1 and PFV integrases (INs). The DNA binding to either of the INs resulted in a fluorescence signal decrease, which is likely due to the fluorescence quenching by aromatic amino acids located near the 3'-end of the processed strand. The fluorescence deviations upon the 3'-processing strongly depended on the sequence of the fluorescein-labeled terminus of the substrate DNA. In the case of HIV-1 IN, a time-dependent fluorescence decrease was detected. Since it correlated with the rate of 3'-processing resulted in the labeled GT dinucleotide accumulation, it might be explained by the fluorescein quenching by a guanosine residue in the single-stranded dinucleotide. The 3'-processing catalyzed by PFV IN led to the fluorescence enhancement. We ascribed it to the migration of the cleaved AT dinucleotide conjugated with fluorescein away from the amino acids that could quench its fluorescence. The fluorescence-based assay was used for the search of new HIV-1 IN inhibitors. Some bisphosphonate derivatives, which are known to block the phosphorolytic activity of HIV-1 reverse transcriptase, were shown to inhibit HIV-1 IN at micromolar concentrations. This property makes bisphosphonates promising agents for the development of HIV-1 inhibitors affecting two viral enzymes.
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Affiliation(s)
- Andrey Anisenko
- Lomonosov Moscow State University, Chemistry Department and Belozersky Institute of Physical and Chemical Biology, Leninskie gory 1/40, Moscow 119991, Russia
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16
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Han YS, Quashie P, Mesplede T, Xu H, Mekhssian K, Fenwick C, Wainberg MA. A high-throughput assay for HIV-1 integrase 3'-processing activity using time-resolved fluorescence. J Virol Methods 2012; 184:34-40. [PMID: 22584270 DOI: 10.1016/j.jviromet.2012.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 04/26/2012] [Accepted: 05/03/2012] [Indexed: 01/08/2023]
Abstract
HIV-1 integrase (HIV-1 IN), a well-validated antiviral drug target, catalyzes multistep reactions to incorporate viral DNA into the genome of the host cell; these include both a 3'-processing (3'P) reaction and a strand transfer reaction. These enzymatic activities can be measured in vitro with short DNA oligonucleotides that mimic a single viral LTR DNA end and purified IN. A highly sensitive and reproducible time-resolved fluorescence (TRF)-based assay for HIV-1 IN 3'P activity is now reported. This assay was optimized with respect to time and concentrations of metal ions, substrate and enzyme. The assay has now been used successfully to measure HIV-1 IN 3'P activity and has been shown to detect the anti-IN activity of several known 3'P inhibition compounds accurately. This assay, which is amenable to high-throughput screening, will be useful for identification of additional HIV-1 IN 3'P inhibitors.
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Affiliation(s)
- Ying-Shan Han
- McGill University AIDS Centre, Lady Davis for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
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17
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Abstract
Fluorescent sensors that make use of DNA structures have become widely useful in monitoring enzymatic activities. Early studies focused primarily on enzymes that naturally use DNA or RNA as the substrate. However, recent advances in molecular design have enabled the development of nucleic acid sensors for a wider range of functions, including enzymes that do not normally bind DNA or RNA. Nucleic acid sensors present some potential advantages over classical small-molecule sensors, including water solubility and ease of synthesis. An overview of the multiple strategies under recent development is presented in this critical review, and expected future developments in microarrays, single molecule analysis, and in vivo sensing are discussed (160 references).
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Affiliation(s)
- Nan Dai
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Eric T. Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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18
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Dumas A, Luedtke NW. Fluorescence properties of 8-(2-pyridyl)guanine "2PyG" as compared to 2-aminopurine in DNA. Chembiochem 2011; 12:2044-51. [PMID: 21786378 DOI: 10.1002/cbic.201100214] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Indexed: 12/24/2022]
Abstract
Because of their environment-sensitive fluorescence quantum yields, base analogues such as 2-aminopurine (2AP), 6-methylisoxanthopterin (6-MI), and 3-methylisoxanthopterin (3-MI) are widely used in nucleic-acid folding and catalysis assays. Emissions from these guanine mimics are quenched by base-stacking interactions and collisions with purine residues. Fluorescent base analogues that remain highly emissive in folded nucleic acids can provide sensitive means to differentiate DNA/RNA structures by participating in energy transfer from proximal ensembles of unmodified nucleobases. The development of new, highly emissive guanine mimics capable of proper base stacking and base-pairing interactions is an important prerequisite to this approach. Here we report a comparison of the most commonly used probe, 2-aminopurine (2AP), to 8-(2-pyridyl)-2'-deoxyguanosine (2PyG). The photophysical properties of these purine derivatives are very different. 2PyG exhibits enhanced fluorescence quantum yields upon its incorporation into folded nucleic acids--approximately 50-fold brighter fluorescence intensity than 2AP in the context of duplex DNA. Due to its bright fluorescence and compatibility with proper DNA folding, 2PyG can be used to accurately quantify energy-transfer efficiencies, whereas 2AP is much less sensitive to structure-specific trends in energy transfer. When using nucleoside monomers, Stern-Volmer plots of 2AP fluorescence revealed upward curvature of F(0) /F upon titration of guanosine monophoshate (GMP), whereas 2PyG exhibited unusual downward curvature of F(0) /F that resulted in a recovery of fluorescence at high GMP concentrations. These results are consistent with the trends observed for 2PyG- and 2AP-containing oligonucleotides, and furthermore suggest that solutions containing high concentrations of GMP can, in some ways, mimic the high local nucleobase densities of folded nucleic acids.
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Affiliation(s)
- Anaëlle Dumas
- Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, Zürich 8057, Switzerland
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19
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Dumas A, Luedtke NW. Highly fluorescent guanosine mimics for folding and energy transfer studies. Nucleic Acids Res 2011; 39:6825-34. [PMID: 21551219 PMCID: PMC3159459 DOI: 10.1093/nar/gkr281] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Guanosines with substituents at the 8-position can provide useful fluorescent probes that effectively mimic guanine residues even in highly demanding model systems such as polymorphic G-quadruplexes and duplex DNA. Here, we report the synthesis and photophysical properties of a small family of 8-substituted-2′-deoxyguanosines that have been incorporated into the human telomeric repeat sequence using phosphoramidite chemistry. These include 8-(2-pyridyl)-2′-deoxyguanosine (2PyG), 8-(2-phenylethenyl)-2′-deoxyguanosine (StG) and 8-[2-(pyrid-4-yl)-ethenyl]-2′-deoxyguanosine (4PVG). On DNA folding and stability, 8-substituted guanosines can exhibit context-dependent effects but were better tolerated by G-quadruplex and duplex structures than pyrimidine mismatches. In contrast to previously reported fluorescent guanine analogs, 8-substituted guanosines exhibit similar or even higher quantum yields upon their incorporation into nucleic acids (Φ = 0.02–0.45). We have used these highly emissive probes to quantify energy transfer efficiencies from unmodified DNA nucleobases to 8-substituted guanosines. The resulting DNA-to-probe energy transfer efficiencies (ηt) are highly structure selective, with ηt(duplex) < ηt(single-strand) < ηt(G-quadruplex). These trends were independent of the exact structural features and thermal stabilities of the G-quadruplexes or duplexes containing them. The combination of efficient energy transfer, high probe quantum yield, and high molar extinction coefficient of the DNA provides a highly sensitive and reliable readout of G-quadruplex formation even in highly diluted sample solutions of 0.25 nM.
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Affiliation(s)
- Anaëlle Dumas
- Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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20
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Schlitt KM, Millen AL, Wetmore SD, Manderville RA. An indole-linked C8-deoxyguanosine nucleoside acts as a fluorescent reporter of Watson-Crick versus Hoogsteen base pairing. Org Biomol Chem 2011; 9:1565-71. [PMID: 21240404 DOI: 10.1039/c0ob00883d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pyrrole- and indole-linked C(8)-deoxyguanosine nucleosides act as fluorescent reporters of H-bonding specificity. Their fluorescence is quenched upon Watson-Crick H-bonding to dC, while Hoogsteen H-bonding to G enhances emission intensity. The indole-linked probe is ∼ 10-fold brighter and shows promise as a fluorescent reporter of Hoogsteen base pairing.
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Affiliation(s)
- Katherine M Schlitt
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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21
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Petroselli G, Dántola ML, Cabrerizo FM, Lorente C, Braun AM, Oliveros E, Thomas AH. Quenching of the fluorescence of aromatic pterins by deoxynucleotides. J Phys Chem A 2010; 113:1794-9. [PMID: 19199487 DOI: 10.1021/jp8101496] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Steady-state and time-resolved studies of the fluorescence of four aromatic unconjugated pterins (pterin (Ptr), 6-(hydroxymethyl)pterin (Hmp), 6-methylpterin (Mep), and 6,7-dimethylpterin (Dmp)) in aqueous solutions in the presence of different nucleotides (2'-deoxyguanosine 5'-monophosphate (dGMP), 2'-deoxyadenosine 5'-monophosphate (dAMP), and 2'-deoxycytosine 5'-monophosphate (dCMP)) have been performed using the single-photon counting technique. The singlet excited states of acid forms of pterins are deactivated by purine nucleotides (dGMP and dAMP) via a combination of dynamic and static processes. The efficiency of the dynamic quenching is high, independently of the nature of the purine base of the nucleotide and of the chemical structure of the substituents linked to the pterin moiety. Analysis of the static quenching indicates that ground-state association between pterins and purine nucleotides takes place, but the formation of the corresponding complexes is significant only at relatively high reactant concentrations. The quenching of the fluorescence of acid forms of pterin derivatives by dCMP, a pyrimidine nucleotide, is slightly less efficient than the quenching by purine nucleotides and is purely dynamic. In alkaline media, the fluorescence quenching is much less efficient than in acidic media, the deactivation by purine nucleotides being purely dynamic, whereas quenching by dCMP is negligible. Possible mechanisms for the quenching of fluorescence of pterin derivatives by the different nucleotides are discussed.
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Affiliation(s)
- Gabriela Petroselli
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Boulevard 113 y 64, 1900 La Plata, Argentina
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22
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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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Jungmann O, Pfleiderer W. Nucleosides part LXVI I: synthesis of 4-amino-7(8H)pteridinone-N8-nucleosides-structural analogs of adenosine. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2010; 28:550-85. [PMID: 20183602 DOI: 10.1080/15257770903054241] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Various 4-amino-7(8H)pteridones (6, 12, 14, 15, 20, 22) have been glycosylated with 1-chloro-2'-deoxy-D-ribofuranose derivatives (25, 26) applying the new DBU-salt method to form the N(8)-2'-deoxy-D-ribofuranosides (27-36) which can be regarded as 2'-deoxyadenosine analogs. Analogously reacted the 2-N,N-dimethyl-amino-methyleneimino-7(8H)pteridones (43-48) to give preferentially the corresponding N(8)-beta-D-anomers (49-55). Ribosylation with 1-bromo-2,3,5-tri-O-benzoyl-a-D-ribofuranose (56) proceeded as well with 6, 12, 15, 45, and 46 to yield to N(8)-beta-D-ribofuranosides 57-61. Sugar deprotection led to the free N(8)-2'-deoxy-beta-D-ribofuranosides 37-42 and N(8)-beta-D-ribofurano-sides 62-65, respectively. Glycosylations via the silyl-method under Vorbruggen conditions led with 6, 12 and 15 to the same results, however, 4-amino-6-phenyl-7(8H)pteridone (14) reacted differently forming the N(1)-beta-D-ribofuranosides (71, 79) and the N(1)-2'-deoxy-alpha-and ss-D-ribofuranosides 73, 74, 77, 78. The assignments of the structures have been achieved by (1)H-NMR- and UV-spectra. C,H,N-elemental analyses account for the composition.
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Affiliation(s)
- Oliver Jungmann
- Fachbereich Chemie, Universitat Konstanz, Postfach, Konstanz, Germany
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24
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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: 658] [Impact Index Per Article: 47.0] [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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25
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Poulin KW, Smirnov AV, Hawkins ME, Balis FM, Knutson JR. Conformational heterogeneity and quasi-static self-quenching in DNA containing a fluorescent guanine analogue, 3MI or 6MI. Biochemistry 2009; 48:8861-8. [PMID: 19610668 PMCID: PMC3412956 DOI: 10.1021/bi9003414] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two different microenvironments in the DNA sequence 5'-act aGa gat ccc tca gac cct ttt agt cag tGt gga-3' (in both single- and double-stranded forms) are explored using two similar fluorescent nucleoside analogues, 3MI and 6MI. Each probe was evaluated in two environments, one strand with the probe flanked by thymines (PTRT) and the other by adenines (PTRA) with positions indicated by G's in the sequence. Both time-resolved anisotropies and lifetimes of the probes depend upon local interactions, and these are altered by duplex formation. Integrals of lifetime curves compared with quantum yields reveal that each probe displays a "dark" component (below detection limits, with a lifetime of <70 ps). For 6MI in PTRA, this QSSQ "quasi-static self-quenching" or "dark" component represents approximately half the molecules, whether in single- or double-stranded form. In PTRT, 6MI displays an unusual increase in the quantum yield upon formation of the double strand (from 0.107 to 0.189) apparently the result of escape from QSSQ which simultaneously declines from 66 to 33%. This is also accompanied by doubling of steady-state anisotropy. Only 6MI in the PTRT duplex displays a rotational correlation time of >7 ns. In other words, the DS 6MI PTRA environment fails to constrain local motion and QSSQ remains the same as in the single strand; in contrast, the flanking T duplex environment restricts local motion and halves QSSQ. We collected both steady-state and time-resolved fluorescence quenching titrations of 3MI and 6MI in solution with the mononucleotides AMP, CMP, GMP, and TMP. The dynamic quenching rank of the free probes (quenching constant, kq: T > A > G > C) is totally different from that of incorporated probes. We hypothesize the production of weak 3MI.C or 6MI.C complexes that are somehow rendered less subject to dynamic quenching by collision with subsequent C molecules.
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Affiliation(s)
- Kristi Wojtuszewski Poulin
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Aleksandr V. Smirnov
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Mary E. Hawkins
- Pharmacology and Experimental Therapeutics Section, Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Frank M. Balis
- Pharmacology and Experimental Therapeutics Section, Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Jay R. Knutson
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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26
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Sandin P, Stengel G, Ljungdahl T, Börjesson K, Macao B, Wilhelmsson LM. Highly efficient incorporation of the fluorescent nucleotide analogs tC and tCO by Klenow fragment. Nucleic Acids Res 2009; 37:3924-33. [PMID: 19401439 PMCID: PMC2709563 DOI: 10.1093/nar/gkp266] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Studies of the mechanisms by which DNA polymerases select the correct nucleotide frequently employ fluorescently labeled DNA to monitor conformational rearrangements of the polymerase-DNA complex in response to incoming nucleotides. For this purpose, fluorescent base analogs play an increasingly important role because they interfere less with the DNA-protein interaction than do tethered fluorophores. Here we report the incorporation of the 5'-triphosphates of two exceptionally bright cytosine analogs, 1,3-diaza-2-oxo-phenothiazine (tC) and its oxo-homolog, 1,3-diaza-2-oxo-phenoxazine (tC(O)), into DNA by the Klenow fragment. Both nucleotide analogs are polymerized with slightly higher efficiency opposite guanine than cytosine triphosphate and are shown to bind with nanomolar affinity to the DNA polymerase active site, according to fluorescence anisotropy measurements. Using this method, we perform competitive binding experiments and show that they can be used to determine the dissociation constant of any given natural or unnatural nucleotide. The results demonstrate that the active site of the Klenow fragment is flexible enough to tolerate base pairs that are size-expanded in the major groove. In addition, the possibility to enzymatically polymerize a fluorescent nucleotide with high efficiency complements the tool box of biophysical probes available to study DNA replication.
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Affiliation(s)
- Peter Sandin
- Department of Chemical and Biological Engineering/Physical Chemistry, Chalmers University of Technology, S-41296 Gothenburg, Sweden
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27
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Engelman A. Mechanistic and pharmacological analyses of HIV-1 integration. Methods 2009; 47:225-8. [PMID: 19389610 PMCID: PMC2709961 DOI: 10.1016/j.ymeth.2009.03.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 03/16/2009] [Indexed: 11/30/2022] Open
Abstract
Significant advances have transpired in the human immunodeficiency virus type 1 (HIV-1) integration field in recent years. Considering its essential nature, integrase has long been a target of interest for antiviral drug development. The most significant advance was the approval of the Merck compound raltegravir, the first licensed integrase inhibitor, in October 2007. Another milestone was the identification and characterization of specific nucleoprotein complexes that mediate integrase 3' processing and DNA strand transfer activities in vitro. Genome-wide distribution analyses have furthermore revealed that different retroviruses differentially target distinctive regions of chromatin during integration. For examples, lentiviruses favor actively transcribed genes whereas gammaretroviruses such as Moloney murine leukemia virus prefer transcriptional start sites. Though the underlying mechanisms are unknown for most retroviruses, the lentiviral preference is in large part guided through the interaction with the integrase binding protein lens epithelium-derived growth factor (LEDGF)/p75. Experimental methods that formed the foundations for each of these advances, as well as other techniques topical to the study of HIV-1 integration, are described in this issue of Methods.
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Affiliation(s)
- Alan Engelman
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, 44 Binney Street, CLSB-1010, Boston, MA 02115, USA, Email address: , Tel: +1 617 632 4361, Fax: +1 617 632 4338
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28
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Merkel G, Andrake MD, Ramcharan J, Skalka AM. Oligonucleotide-based assays for integrase activity. Methods 2008; 47:243-8. [PMID: 19010419 DOI: 10.1016/j.ymeth.2008.10.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/20/2008] [Accepted: 10/22/2008] [Indexed: 12/01/2022] Open
Abstract
Oligonucleotide assays have been invaluable for elucidation of the molecular mechanisms of retroviral integrases. A suite of rapid and sensitive fluorescence assays to measure the DNA binding, processing, and joining activities of integrase (IN) is described here. The assays are especially useful for characterizing the major activities of the enzyme, and for handling large numbers of samples efficiently. They can greatly facilitate further biochemical and structural analyses for HIV-1 and other IN proteins. The assays can also be adapted for moderate-high throughput testing of various inhibitory compounds.
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Affiliation(s)
- George Merkel
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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29
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Wilson JN, Cho Y, Tan S, Cuppoletti A, Kool ET. Quenching of Fluorescent Nucleobases by Neighboring DNA: The “Insulator” Concept. Chembiochem 2008; 9:279-85. [DOI: 10.1002/cbic.200700381] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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30
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Abstract
This chapter is focused on the fluorescent pteridine guanine analogs, 3MI and 6MI and on the pteridine adenine analog, 6MAP. A brief overview of commonly used methods to fluorescently label oligonucleotides reveals the role the pteridines play in the extensive variety of available probes. We describe the fluorescence characteristics of the pteridine probes as monomers and incorporated into DNA and review a variety of applications including changes in fluorescence intensity, anisotropies, time resolved studies, two photon excitation and single molecule detection.
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31
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Sandin P, Börjesson K, Li H, Mårtensson J, Brown T, Wilhelmsson LM, Albinsson B. Characterization and use of an unprecedentedly bright and structurally non-perturbing fluorescent DNA base analogue. Nucleic Acids Res 2007; 36:157-67. [PMID: 18003656 PMCID: PMC2248743 DOI: 10.1093/nar/gkm1006] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
This article presents the first evidence that the DNA base analogue 1,3-diaza-2-oxophenoxazine, tC(O), is highly fluorescent, both as free nucleoside and incorporated in an arbitrary DNA structure. tC(O) is thoroughly characterized with respect to its photophysical properties and structural performance in single- and double-stranded oligonucleotides. The lowest energy absorption band at 360 nm (epsilon = 9000 M(-1) cm(-1)) is dominated by a single in-plane polarized electronic transition and the fluorescence, centred at 465 nm, has a quantum yield of 0.3. When incorporated into double-stranded DNA, tC(O) shows only minor variations in fluorescence intensity and lifetime with neighbouring bases, and the average quantum yield is 0.22. These features make tC(O), on average, the brightest DNA-incorporated base analogue so far reported. Furthermore, it base pairs exclusively with guanine and causes minimal perturbations to the native structure of DNA. These properties make tC(O) a promising base analogue that is perfectly suited for e.g. photophysical studies of DNA interacting with macromolecules (proteins) or for determining size and shape of DNA tertiary structures using techniques such as fluorescence anisotropy and fluorescence resonance energy transfer (FRET).
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Affiliation(s)
- Peter Sandin
- Department of Chemical and Biological Engineering/Physical Chemistry, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
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32
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Nonogawa M, Pack SP, Arai T, Endo N, Sommani P, Kodaki T, Kotake Y, Makino K. Synthesis of 6-formylpterin nucleoside analogs and their ROS generation activities in the presence of NADH in the dark. Org Biomol Chem 2007; 5:3314-9. [PMID: 17912384 DOI: 10.1039/b710466a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We demonstrated previously that 3-position-modified 6-formylpterin (6FP) derivatives produce reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) from oxygen in the presence of NADH in the dark. It has been shown that 6FP derivatives markedly generate ROS, which gives rise to their particular physiological activities, such as induction of apoptosis in cellular and living systems, suggesting that such compounds provide a hint for the design of a ROS controlling agent in vivo. However, it is not well understood why such unique activities appear on chemical modification. In the present study, in order to see the effect on ROS generation activity in the dark by the modification of the 1-position in 6FP, we have developed a new synthetic procedure for nucleoside analogs of 6FP and prepared 1-(beta-d-ribofuranosyl)-2-(N,N-diethylaminomethyleneamino)-6-formylpteridin-4-one (RDEF) and 1-(beta-d-ribofuranosyl)-2-(piperidine-1-ylmethyleneamino)-6-formylpteridin-4-one (RPIF) in which the 1-position of 6FP is glycosylated. At pH 7.4, NADH was spontaneously oxidized to NAD(+) in the presence of RDEF in the dark. Using electron paramagnetic resonance analysis coupled with the spin trapping technique, we show that O(2) was converted to H(2)O(2)via superoxide anion radical ( O(2)(-)) during this reaction. The modification of the 1-position of 6FP did not cancel ROS generation activities, which were demonstrated in 3-position-modified 6FPs. Since the 6FP derivatives developed in the present study have a ribose moiety, these compounds can be subjected to further derivatization, such as incorporation into oligonucleotides, oligosaccharides, proteins, or any other compounds that recognize and interact with specific biomolecules, and therefore would be useful in pharmaceutical investigations that need generation of appropriate and controllable amounts of ROS in vivo.
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Affiliation(s)
- Mitsuru Nonogawa
- Institute of Advanced Energy, Kyoto University, Gokasho, Uji 611-0011, Japan
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Shi ZD, Wu H, Ruddy B, Griffiths GL. Imaging Probe Development Center: a National Institutes of Health core synthesis resource for imaging probes. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:051502. [PMID: 17994866 DOI: 10.1117/1.2778702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The Imaging Probe Development Center (IPDC) has been set up under the auspices of the National Institutes of Health (NIH) Roadmap as part of the molecular libraries and imaging initiatives. It comprises a core synthesis facility dedicated to the preparation of imaging probes, initially for intramural NIH scientists, and later, for the extramural scientific community. The facility opened fully in late 2006, in refurbished laboratories in Rockville, Maryland, and a staff of around a dozen was recruited into place by early 2007; the director was hired in late 2005. The IPDC provides a mechanism for the production of sensitive probes for use by imaging scientists who cannot obtain such probes commercially. The probes to be made will encompass all major imaging modalities including radionuclide, magnetic resonance, and optical. The operation of the IPDC is outlined, together with the results of interim achievements while the IPDC maintained a small temporary laboratory in Bethesda. As of December 2006, a total of eleven probe compositions had been made, and several of these are described with particular mention of those probes intended for use in optical applications.
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Affiliation(s)
- Zhen-Dan Shi
- National Institutes of Health, Imaging Probe Development Center, National Heart, Lung, and Blood Institute, 9800 Medical Center Drive, Building 2B, Suite 3042, Bethesda, Maryland 20892, USA
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Chen X, Xu X, Cao Z. Theoretical Study on the Singlet Excited State of Pterin and Its Deactivation Pathway. J Phys Chem A 2007; 111:9255-62. [PMID: 17629256 DOI: 10.1021/jp0727502] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The excited-state properties and related photophysical processes of the acidic and basic forms of pterin have been investigated by the density functional theory and ab initio methodologies. The solvent effects on the low-lying states have been estimated by the polarized continuum model and combined QM/MM calculations. Calculations reveal that the observed two strong absorptions arise from the strong pi --> pi* transitions to 1(pipi*L(a)) and 1(pipi*L(b)) in the acidic and basic forms of pterin. The first 1(pipi*L(a)) excited state is exclusively responsible for the experimental emission band. The vertical 1(n(N)pi*) state with a small oscillator strength, slightly higher in energy than the 1(pipi*L(a)) state, is less accessible by the direct electronic transition. The 1(n(N)pi*) state may be involved in the photophysical process of the excited pterin via the 1(pipi*L(a)/n(N)pi*) conical intersection. The radiationless decay of the excited PT to the ground state experiences a barrier of 13.8 kcal/mol for the acidic form to reach the (S(1)/S(0)) conical intersection. Such internal conversion can be enhanced with the increase in excitation energy, which will reduce the fluorescence intensity as observed experimentally.
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Affiliation(s)
- Xing Chen
- Department of Chemistry and State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen 361005, China
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35
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Sandin P, Lincoln P, Brown T, Wilhelmsson LM. Synthesis and oligonucleotide incorporation of fluorescent cytosine analogue tC: a promising nucleic acid probe. Nat Protoc 2007; 2:615-23. [PMID: 17406622 DOI: 10.1038/nprot.2007.80] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The tricyclic cytosine, tC, is a fluorescent base analogue with excellent properties for investigating intrinsic characteristics of nucleic acid as well as interactions between nucleic acids and other molecules. Its unique fluorescence properties and insignificant influence on overall structure and dynamics of nucleic acid after incorporation makes tC particularly interesting in fluorescence resonance energy transfer and anisotropy measurements. We here describe a straightforward synthesis of the standard monomer form of tC for DNA solid-phase synthesis, the tC phosphoramidite, and its subsequent incorporation into oligonucleotides. The total synthesis of the tC phosphoramidite takes approximately 8 days and its incorporation and the subsequent oligonucleotide purification an additional day.
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Affiliation(s)
- Peter Sandin
- Department of Chemical and Biological Engineering/Physical Chemistry, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
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36
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He HQ, Ma XH, Liu B, Zhang XY, Chen WZ, Wang CX, Cheng SH. High-throughput real-time assay based on molecular beacons for HIV-1 integrase 3'-processing reaction. Acta Pharmacol Sin 2007; 28:811-7. [PMID: 17506940 DOI: 10.1111/j.1745-7254.2007.00561.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
AIM To develop a high-throughput real-time assay based on molecular beacons to monitor the integrase 3'-processing reaction in vitro and apply it to inhibitor screening. METHODS The recombinant human immunodeficiency virus (HIV)-1 integrase (IN) is incubated with a 38 mer oligonucleotide substrate, a sequence identical to the U5 end of HIV-1 long terminal repeats (LTR). Based on the fluorescence properties of molecular beacons, the substrate is designed to form a stem-loop structure labeled with a fluorophore at the 5' end and a quencher at the 3' end. IN cleaves the terminal 3'-dinucleotide containing the quencher, resulting in an increase in fluorescence which can be monitored on a spectrofluorometer. To optimize this assay, tests were performed to investigate the effects of substrates, enzyme and the metal ion concentrations on the IN activity and optimal parameters were obtained. Moreover, 2 IN inhibitors were employed to test the performance of this assay in antiviral compound screening. RESULTS The fluorescent intensity of the reaction mixture varies linearly with time and is proportional to the velocity of the 3'-processing reaction. Tests were performed and the results showed that the optimal rate was obtained for a reaction mixture containing 50 mg/L recombinant HIV-1 IN, 400 nmol/L substrate, and 10 mmol/L Mn(2+). The IN 3'-processing reaction under the optimal conditions showed a more than 18-fold increase in the fluorescence intensity compared to the enzyme-free control. The IC50 values of the IN inhibitors obtained in our assay were similar to the values obtained from a radiolabeled substrate assay. CONCLUSION Our results demonstrated that this is a fast, reliable, and sensitive method to monitor HIV IN 3'-processing reaction and that it can be used for inhibitor screening.
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Affiliation(s)
- Hong-Qiu He
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100022, China
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37
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Singleton SF, Roca AI, Lee AM, Xiao J. Probing the structure of RecA-DNA filaments. Advantages of a fluorescent guanine analog. Tetrahedron 2007; 63:3553-3566. [PMID: 17955055 PMCID: PMC2031864 DOI: 10.1016/j.tet.2006.10.092] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The RecA protein of Escherichia coli plays a crucial roles in DNA recombination and repair, as well as various aspects of bacterial pathogenicity. The formation of a RecA-ATP-ssDNA complex initiates all RecA activities and yet a complete structural and mechanistic description of this filament has remained elusive. An analysis of RecA-DNA interactions was performed using fluorescently labeled oligonucleotides. A direct comparison was made between fluorescein and several fluorescent nucleosides. The fluorescent guanine analog 6-methylisoxanthopterin (6MI) demonstrated significant advantages over the other fluorophores and represents an important new tool for characterizing RecA-DNA interactions.
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Affiliation(s)
- Scott F. Singleton
- Division of Medicinal Chemistry & Natural Products, School of Pharmacy, The University of North Carolina at Chapel Hill, CB 7360, Chapel Hill, NC 27599-7360, USA
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38
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Hawkins ME. Synthesis, purification and sample experiment for fluorescent pteridine-containing DNA: tools for studying DNA interactive systems. Nat Protoc 2007; 2:1013-21. [PMID: 17446875 DOI: 10.1038/nprot.2007.150] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fluorescent nucleoside analogs provide a means to study DNA interactive systems through direct measurement of fluorescence properties. As integrated parts of DNA, these probes provide opportunities for monitoring subtle changes in DNA structure as it meets and reacts with other molecules. This protocol describes modifications to standard DNA synthesis to efficiently use smaller volumes of the probe phosphoramidite, purification of pteridine-containing sequences and a deprotection procedure specific for 6MI-containing sequences. Yields for probe incorporation in DNA synthesis are comparable to those for standard phosphoramidites. Examples of the fluorescence signals one can expect are described. Automated synthesis, which is dependent on the length of the sequence, takes about 4-5 h for a 20-mer. The deprotection of 6MI-containing sequences takes approximately 6-7 h before the standard ammonium hydroxide overnight incubation. Purification through polyacrylamide gels, electroelution and ethanol precipitation can be accomplished in 6-8 h.
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Affiliation(s)
- Mary E Hawkins
- National Cancer Institute, NIH, Pediatric Oncology Branch, 10 Center Drive, CRC 1-3872, Bethesda, Maryland 20854, USA.
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39
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40
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Wilson JN, Kool ET. Fluorescent DNA base replacements: Reporters and sensors for biological systems. Org Biomol Chem 2006; 4:4265-74. [PMID: 17102869 DOI: 10.1039/b612284c] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We describe the design, synthesis, and properties of nucleoside monomers in which the DNA base is replaced by fluorescent hydrocarbons and heterocycles, and the assembly of these monomers into DNA-like molecules in which the all bases are fluorescent. As monomers, such molecules have useful applications as reporters in the DNA context. The use of fluorescent DNA bases, rather than more traditional fluorophores tethered to the DNA strand, gives a more predictable location and orientation, and yields a more direct response to changes that occur within the helix. In addition to uses as monomers, such compounds can be assembled into polychromophoric oligomers ("oligodeoxyfluorosides" or ODFs). ODFs are water soluble, discrete molecules and are easily arranged into specific sequences by use of a DNA synthesizer. They have displayed a number of properties not readily available in commercial fluorophores, including large Stokes shifts, tunable excitation and emission wavelengths, and sensing responses to physical changes or molecular species in solution. We describe an approach to assembling and screening large sets of oligofluorosides for rapid identification of molecules with desirable properties. Such compounds show promise for applications in biochemistry, biology, environmental and materials applications.
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Affiliation(s)
- James N Wilson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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41
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Jungmann O, Pfleiderer W. Pteridine Nucleosides Analogs of 2′-Deoxyadenosine as Building Blocks for Oligonucleotide Synthesis. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/07328319708002964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Oliver Jungmann
- a Fakultät für Chemie Universität Konstanz , Postfach 5560, D-78434, Konstanz , Germany
| | - Wolfgang Pfleiderer
- a Fakultät für Chemie Universität Konstanz , Postfach 5560, D-78434, Konstanz , Germany
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42
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Lehbauer J, Pfleidere W. Synthesis of 8-(2-Deoxy-β-D-Ribofuranosyl)-Isoxanthopterins New Fluorescent Analogs of 2′-Deoxyguanosine. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/07328319708002965] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Jörg Lehbauer
- a Fakultät für Chemie, Universität Konstanz , Postfach 5560, D-78434, Konstanz , Germany
| | - Wolfgang Pfleidere
- a Fakultät für Chemie, Universität Konstanz , Postfach 5560, D-78434, Konstanz , Germany
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43
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Guiot E, Carayon K, Delelis O, Simon F, Tauc P, Zubin E, Gottikh M, Mouscadet JF, Brochon JC, Deprez E. Relationship between the oligomeric status of HIV-1 integrase on DNA and enzymatic activity. J Biol Chem 2006; 281:22707-19. [PMID: 16774912 DOI: 10.1074/jbc.m602198200] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The 3'-processing of the extremities of viral DNA is the first of two reactions catalyzed by HIV-1 integrase (IN). High order IN multimers (tetramers) are required for complete integration, but it remains unclear which oligomer is responsible for the 3'-processing reaction. Moreover, IN tends to aggregate, and it is unknown whether the polymerization or aggregation of this enzyme on DNA is detrimental or beneficial for activity. We have developed a fluorescence assay based on anisotropy for monitoring release of the terminal dinucleotide product in real-time. Because the initial anisotropy value obtained after DNA binding and before catalysis depends on the fractional saturation of DNA sites and the size of IN.DNA complexes, this approach can be used to study the relationship between activity and binding/multimerization parameters in the same assay. By increasing the IN:DNA ratio, we found that the anisotropy increased but the 3'-processing activity displayed a characteristic bell-shaped behavior. The anisotropy values obtained in the first phase were predictive of subsequent activity and accounted for the number of complexes. Interestingly, activity peaked and then decreased in the second phase, whereas anisotropy continued to increase. Time-resolved fluorescence anisotropy studies showed that the most competent form for catalysis corresponds to a dimer bound to one viral DNA end, whereas higher order complexes such as aggregates predominate during the second phase when activity drops off. We conclude that a single IN dimer at each extremity of viral DNA molecules is required for 3'-processing, with a dimer of dimers responsible for the subsequent full integration.
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Affiliation(s)
- Elvire Guiot
- Laboratoire de Biotechnologie et Pharmacologie Genetique Appliquee, CNRS, UMR8113, Ecole Normale Supérieure de Cachan, 61 av du Président Wilson, 94235 Cachan, France
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Smolov M, Gottikh M, Tashlitskii V, Korolev S, Demidyuk I, Brochon JC, Mouscadet JF, Deprez E. Kinetic study of the HIV-1 DNA 3'-end processing. FEBS J 2006; 273:1137-51. [PMID: 16519680 DOI: 10.1111/j.1742-4658.2006.05139.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The 3'-processing of viral DNA extremities is the first step in the integration process catalysed by human immunodeficiency virus (HIV)-1 integrase (IN). This reaction is relatively inefficient and processed DNAs are usually detected in vitro under conditions of excess enzyme. Despite such experimental conditions, steady-state Michaelis-Menten formalism is often applied to calculate characteristic equilibrium/kinetic constants of IN. We found that the amount of processed product was not significantly affected under conditions of excess DNA substrate, indicating that IN has a limited turnover for DNA cleavage. Therefore, IN works principally in a single-turnover mode and is intrinsically very slow (single-turnover rate constant = 0.004 min(-1)), suggesting that IN activity is mainly limited at the chemistry step or at a stage that precedes chemistry. Moreover, fluorescence experiments showed that IN-DNA product complexes were very stable over the time-course of the reaction. Binding isotherms of IN to DNA substrate and product also indicate tight binding of IN to the reaction product. Therefore, the slow cleavage rate and limited product release prevent or greatly reduce subsequent turnover. Nevertheless, the time-course of product formation approximates to a straight line for 90 min (apparent initial velocity), but we show that this linear phase is due to the slow single-turnover rate constant and does not indicate steady-state multiple turnover. Finally, our data ruled out the possibility that there were large amounts of inactive proteins or dead-end complexes in the assay. Most of complexes initially formed were active although dramatically slow.
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Affiliation(s)
- Maksim Smolov
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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45
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Xiao J, Lee AM, Singleton SF. Construction and evaluation of a kinetic scheme for RecA-mediated DNA strand exchange. Biopolymers 2006; 81:473-96. [PMID: 16421856 DOI: 10.1002/bip.20446] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The Escherichia coli RecA protein is the prototype of a class of proteins playing a central role in genomic repair and recombination in all organisms. The unresolved mechanistic strategy by which RecA aligns a single strand of DNA with a duplex DNA and mediates a DNA strand switch is central to understanding its recombinational activities. Toward a molecular-level understanding of RecA-mediated DNA strand exchange, we explored its mechanism using oligonucleotide substrates and the intrinsic fluorescence of 6-methylisoxanthopterin (6MI). Steady- and presteady-state spectrofluorometric data demonstrate that the reaction proceeds via a sequential four-step mechanism comprising a rapid, bimolecular association step followed by three slower unimolecular steps. Previous authors have proposed multistep mechanisms involving two or three steps. Careful analysis of the differences among the experimental systems revealed a previously undiscovered intermediate (N1) whose formation may be crucial in the kinetic discrimination of homologous and heterologous sequences. This observation has important implications for probing the fastest events in DNA strand exchange using 6MI to further elucidate the molecular mechanisms of recombination and recombinational repair.
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Affiliation(s)
- Jie Xiao
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA
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46
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Sandin P, Wilhelmsson LM, Lincoln P, Powers VEC, Brown T, Albinsson B. Fluorescent properties of DNA base analogue tC upon incorporation into DNA--negligible influence of neighbouring bases on fluorescence quantum yield. Nucleic Acids Res 2005; 33:5019-25. [PMID: 16147985 PMCID: PMC1201328 DOI: 10.1093/nar/gki790] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The quantum yield of the fluorescent tricyclic cytosine analogue, 1,3-diaza-2-oxophenothiazine, tC, is high and virtually unaffected by incorporation into both single- and double-stranded DNA irrespective of neighbouring bases (0.17-0.24 and 0.16-0.21, respectively) and the corresponding fluorescence decay curves are all mono-exponential, properties that are unmatched by any base analogue so far. The fluorescence lifetimes increase when going from tC free in solution (3.2 ns) to single- and double-stranded DNA (on average 5.7 and 6.3 ns, respectively). The mono-exponential decays further support previous NMR results where it was found that tC has a well-defined position and geometry within the DNA helix. Furthermore, we find that the oxidation potential of tC is 0.4 V lower than for deoxyguanosine, the natural base with the lowest oxidation potential. This suggests that tC may be of interest in charge transfer studies in DNA as an electron hole acceptor. We also present a novel synthetic route to the phosphoramidite form of tC. The results presented here together with previous work show that tC is a very good C-analogue that induces minimal perturbation to the native structure of DNA. This makes tC unique as a fluorescent base analogue and is thus highly interesting in a range of applications for studying e.g. structure, dynamics and kinetics in nucleic acid systems.
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Affiliation(s)
| | - L. Marcus Wilhelmsson
- To whom the correspondence should be addressed. Tel: +46 31 7723051; Fax: +46 31 7723858;
| | | | - Vicki E. C. Powers
- School of Chemistry, University of SouthamptonHighfield, Southampton SO17 1BJ, UK
| | - Tom Brown
- School of Chemistry, University of SouthamptonHighfield, Southampton SO17 1BJ, UK
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47
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Cabrerizo FM, Petroselli G, Lorente C, Capparelli AL, Thomas AH, Braun AM, Oliveros E. Substituent Effects on the Photophysical Properties of Pterin Derivatives in Acidic and Alkaline Aqueous Solutions. Photochem Photobiol 2005; 81:1234-40. [PMID: 16225380 DOI: 10.1562/2005-05-10-ra-522] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pterins are heterocyclic compounds with important biological functions, and most of them may exist in two acid-base forms in the pH range between 3 and 13 in aqueous solution. In this work, the photophysical properties of acid and basic forms of six compounds of the pterin family (6-hydroxymethylpterin [HPT], 6-methylpterin [MPT], 6,7-dimethylpterin [DPT], rhamnopterin [RPT], N-methylfolic acid [MFA], and pteroic acid [PA]) have been studied. The effects of the chemical nature of the substituents at position 6 of the pterin moiety and the effects of the pH on the absorption and emission properties are analyzed. The fluorescence characteristics (spectra, quantum yields, lifetimes) of these compounds have been investigated using the single-photon-counting technique. Results obtained for pterin derivatives containing small substituents with 1 carbon atom (HPT, MPT, DPT) and short hydrocarbon chain (4 carbon atoms) (RPT) are different from those found for pterin derivatives containing a p-aminobenzoic acid (PABA) moiety in the substituent (MFA and PA). Fluorescence quantum yields (Phi(F)) of the first group of compounds are relatively high (>/=0.4), whereas MFA and PA exhibit very small Phi(F) values (</=0.01).
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Affiliation(s)
- Franco M Cabrerizo
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4 (1900) La Plata, Argentina
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48
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Affiliation(s)
- Kazuhiko Nakatani
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8150, Japan.
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49
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Matysiak S, Waldscheck B, Pfleiderer W. Nucleosides. LXV. Synthesis of new pteridine-N8-nucleosides. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2004; 23:51-66. [PMID: 15043136 DOI: 10.1081/ncn-120027817] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A general synthetic approach to various isoxanthopterin-nucleosides starting from 6-methyl-2-methylthio-4(3H),7(8H)-pterdinedione (1) has been developed. Ribosylation with 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose via the silyl-method led to 2 and reaction with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-ribofuranose using the DBU-method afforded 28. Protection of the amide function at O4 by benzylation to 5 and by a Mitsunobu reaction with 2-(4-nitrophenyl)ethanol to 29 gave soluble intermediates which can be oxidized to the corresponding 2-methylsulfonyl derivatives 8 and 30, respectively. Nucleophilic displacement reactions of the highly reactive 2-methylsulfonyl functions by various amines proceeded under mild conditions to isoxanthopterin-N8-ribo- (11-17) and 2'-deoxyribomucleosides (31-33). Debenzylation can be achieve by Pd-catalyzed hydrogenation (9 to 19) and cleavage of the npe-protecting group (31, 32 to 34, 35) works well with DBU by beta-elimination.
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Engman KC, Sandin P, Osborne S, Brown T, Billeter M, Lincoln P, Nordén B, Albinsson B, Wilhelmsson LM. DNA adopts normal B-form upon incorporation of highly fluorescent DNA base analogue tC: NMR structure and UV-Vis spectroscopy characterization. Nucleic Acids Res 2004; 32:5087-95. [PMID: 15452275 PMCID: PMC521657 DOI: 10.1093/nar/gkh844] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The influence of the highly fluorescent tricyclic cytosine base analogue (tC) on duplex DNA conformation is investigated. The duplex properties are characterized by absorbance and circular dichroism (CD) for all combinations of neighbouring bases to tC, and an NMR structure is determined for one tC-containing sequence. For the oligonucleotides with one tC incorporated instead of cytosine, the melting temperature is increased on average by 2.7 degrees C above that for the unmodified ones. CD spectra are practically identical for modified and unmodified sequences, indicating an unperturbed B-DNA conformation. The NMR structure determination of the self-complementary sequence 5'-CTC(tC)ACGTGGAG shows a DNA conformation consistent with B-form for the whole duplex. The root-mean-square distance for the nucleotides of the eight central base pairs between the 10 structures with lowest CYANA target functions and a mean structure is 0.45 +/- 0.17 A. The NMR data confirm correct base pairing for tC by the observation of both intrastrand and interstrand imino proton NOEs. Altogether, this suggests that tC works well as a cytosine analogue, i.e. it is situated in the base stack, forming hydrogen bonds with G in the complementary strand, without distorting the DNA backbone conformation. This first example of an artificial, highly fluorescent DNA base that does not perturb the DNA conformation could have valuable applications for the study of the structure and dynamics of nucleic acid systems.
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Affiliation(s)
- K Cecilia Engman
- Department of Chemistry, Göteborg University, PO Box 462, SE-40530 Gothenburg, Sweden
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