1
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Moscato D, Gabas F, Conte R, Ceotto M. Vibrational spectroscopy simulation of solvation effects on a G-quadruplex. J Biomol Struct Dyn 2023; 41:14248-14258. [PMID: 36856120 DOI: 10.1080/07391102.2023.2180435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 02/07/2023] [Indexed: 03/02/2023]
Abstract
It is commonly believed that solvation effects on the vibrational properties of a solute are easily accounted for by simple rules of thumbs, that is, solvating a polar molecule in a polar medium has the only effect of red shifting all its spectroscopical features and, similarly, solvating a polar molecule in a nonpolar medium has the opposite effect. In this work, we use theoretical vibrational spectroscopy at quasi-classical and quantum approximate semiclassical level to gain atomistic insights about solvent-solute interactions for 2'-deoxyguanosine and the G-quadruplex. We employ the quasi-classical trajectory method to include full anharmonicity into our calculated spectra, and then introduce quantum nuclear effects by means of divide-and-conquer semiclassical spectroscopy calculations. Solvation is treated explicitly leading to a good reproducibility of the available experimental data and reliable predictions when an experimental reference is missing.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Davide Moscato
- Dipartimento di Chimica, Università degli Studi di Milano, Milano, Italy
| | - Fabio Gabas
- Dipartimento di Chimica, Università degli Studi di Milano, Milano, Italy
| | - Riccardo Conte
- Dipartimento di Chimica, Università degli Studi di Milano, Milano, Italy
| | - Michele Ceotto
- Dipartimento di Chimica, Università degli Studi di Milano, Milano, Italy
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2
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Largy E, König A, Ghosh A, Ghosh D, Benabou S, Rosu F, Gabelica V. Mass Spectrometry of Nucleic Acid Noncovalent Complexes. Chem Rev 2021; 122:7720-7839. [PMID: 34587741 DOI: 10.1021/acs.chemrev.1c00386] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nucleic acids have been among the first targets for antitumor drugs and antibiotics. With the unveiling of new biological roles in regulation of gene expression, specific DNA and RNA structures have become very attractive targets, especially when the corresponding proteins are undruggable. Biophysical assays to assess target structure as well as ligand binding stoichiometry, affinity, specificity, and binding modes are part of the drug development process. Mass spectrometry offers unique advantages as a biophysical method owing to its ability to distinguish each stoichiometry present in a mixture. In addition, advanced mass spectrometry approaches (reactive probing, fragmentation techniques, ion mobility spectrometry, ion spectroscopy) provide more detailed information on the complexes. Here, we review the fundamentals of mass spectrometry and all its particularities when studying noncovalent nucleic acid structures, and then review what has been learned thanks to mass spectrometry on nucleic acid structures, self-assemblies (e.g., duplexes or G-quadruplexes), and their complexes with ligands.
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Affiliation(s)
- Eric Largy
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Alexander König
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Anirban Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Debasmita Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Sanae Benabou
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Frédéric Rosu
- Univ. Bordeaux, CNRS, INSERM, IECB, UMS 3033, F-33600 Pessac, France
| | - Valérie Gabelica
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
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3
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Martín‐Arroyo M, Prado A, Chamorro R, Bilbao N, González‐Rodríguez D. Elucidating Noncovalent Reaction Mechanisms: G‐Quartet as an Intermediate in G‐Quadruplex Assembly. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201916261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Miguel Martín‐Arroyo
- Nanostructured Molecular Systems and Materials (MSMn) Group Departamento de Química Orgánica Facultad de Ciencias Universidad Autónoma de Madrid 28049 Madrid Spain
| | - Anselmo Prado
- Nanostructured Molecular Systems and Materials (MSMn) Group Departamento de Química Orgánica Facultad de Ciencias Universidad Autónoma de Madrid 28049 Madrid Spain
| | - Raquel Chamorro
- Nanostructured Molecular Systems and Materials (MSMn) Group Departamento de Química Orgánica Facultad de Ciencias Universidad Autónoma de Madrid 28049 Madrid Spain
| | - Nerea Bilbao
- Nanostructured Molecular Systems and Materials (MSMn) Group Departamento de Química Orgánica Facultad de Ciencias Universidad Autónoma de Madrid 28049 Madrid Spain
| | - David González‐Rodríguez
- Nanostructured Molecular Systems and Materials (MSMn) Group Departamento de Química Orgánica Facultad de Ciencias Universidad Autónoma de Madrid 28049 Madrid Spain
- Institute for Advanced Research in Chemical Sciences (IAdChem) Universidad Autónoma de Madrid 28049 Madrid Spain
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4
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Martín-Arroyo M, Del Prado A, Chamorro R, Bilbao N, González-Rodríguez D. Elucidating Noncovalent Reaction Mechanisms: G-Quartet as an Intermediate in G-Quadruplex Assembly. Angew Chem Int Ed Engl 2020; 59:9041-9046. [PMID: 32125063 DOI: 10.1002/anie.201916261] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/17/2020] [Indexed: 12/20/2022]
Abstract
In analogy to covalent reactions, the understanding of noncovalent association pathways is fundamental to influence and control any supramolecular process. Following an approach that is reminiscent of covalent methodologies, we study here, for the first time, the mechanism of G-quadruplex formation in organic solvents. Our results support a reaction pathway in which the cation shifts the equilibrium towards a G-quartet transient intermediate, which then acts as a template in the formation of the G-quadruplex product.
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Affiliation(s)
- Miguel Martín-Arroyo
- Nanostructured Molecular Systems and Materials (MSMn) Group, Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Anselmo Del Prado
- Nanostructured Molecular Systems and Materials (MSMn) Group, Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Raquel Chamorro
- Nanostructured Molecular Systems and Materials (MSMn) Group, Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Nerea Bilbao
- Nanostructured Molecular Systems and Materials (MSMn) Group, Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - David González-Rodríguez
- Nanostructured Molecular Systems and Materials (MSMn) Group, Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049, Madrid, Spain.,Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049, Madrid, Spain
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5
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Lee C, Choi YK, Lee S, Han SY. Hydrogen bonding influences collision-induced dissociation of Na + -bound guanine tetrads. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 56:e4582. [PMID: 33085179 DOI: 10.1002/jms.4582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/25/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
Na+ -bound guanine (G)-tetrads possess square planar structures formed solely by noncovalent interactions including multiple hydrogen bonds. Unlike G-tetrads facilitated by other alkali metal ions, an intriguing behavior in collision-induced dissociation (CID) has been observed in Na+ -bound G-tetrads, which features a preferential, simultaneous loss of two G ligands in the low energy regime. To understand this unique behavior, we investigated the CID of Na+ -bound G-tetrads with mixed ligands of G and 9-methylguanine (9mG), [Na·Gm ·9mGn ]+ (m + n = 4), and [Li·9mG4 ]+ for comparison. In the CID experiments, the simultaneous losses of two ligands were by far more pronounced than the loss of a single ligand for all five Na+ -bound G-tetrads. However, it appeared that the CID of [Li·9mG4 ]+ prefers to lose single ligands sequentially. An analysis of the fragment abundances suggested that the generation of Na+ -bound dimeric fragments might have occurred with two adjacent ligands. This theoretical study predicted for [Li·9mG4 ]+ that the loss of a single ligand is more energetically favorable than the production of neutral hydrogen-bonded fragments by 35.5 kJ/mol (ΔG). This contradicts our previous calculations for [Na·9mG4 ]+ that a neutral loss of hydrogen-bonded dimers provides the lowest energy product state of Na+ -bound dimeric fragments, which is lower than that of Na+ -bound trimeric fragments by 15.6 kJ/mol. From the results, this comparative study suggests that the pronounced generation of Na+ -bound dimeric fragments in CID of the G-tetrads is likely promoted by the dissociation pathway associated with neutral loss of hydrogen-bonded dimers. It thus demonstrates that multiple hydrogen bonding participating in formation of Na+ -bound G-tetrads may also strongly influence the fate of dissociating complexes of G-tetrads.
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Affiliation(s)
- Chaewon Lee
- Department of Chemistry, Gachon University, Seongnam-si, Republic of Korea
| | - Yoon Kyung Choi
- Department of Chemistry, Gachon University, Seongnam-si, Republic of Korea
| | - Sanghun Lee
- Department of Chemistry, Gachon University, Seongnam-si, Republic of Korea
| | - Sang Yun Han
- Department of Chemistry, Gachon University, Seongnam-si, Republic of Korea
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Cheng R, Martens J, Fridgen TD. A vibrational spectroscopic and computational study of gaseous protonated and alkali metal cationized G-C base pairs. Phys Chem Chem Phys 2020; 22:11546-11557. [PMID: 32395733 DOI: 10.1039/d0cp00069h] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures and properties of metal cationized complexes of 9-ethylguanine (9eG) and 1-methylcytosine (1mC), (9eG:1mC)M+, where M+ = Li+, Na+, K+, Rb+, Cs+ as well as the protonated complex, (9eG:1mC)H+, have been studied using a combination of IRMPD spectroscopy and computational methods. For (9eG:1mC)H+, the dominant structure is a Hoogsteen type complex with the proton covalently bound to N3 of 1mC despite this being the third best protonation site of the two bases; based on proton affinities N7 of 9eG should be protonated. However, this structural oddity can be explained considering both the number of hydrogen bonds that can be formed when N3 of 1mC is protonated as well as the strong ion-induced dipole interaction that exists between an N3 protonated 1mC and 9eG due to the higher polarizability of 9eG. The anomalous dissociation of (9eG:1mC)H+, forming much more (1mC)H+ than would be predicted based on the computed thermochemistry, can be explained as being due to the structural oddity of the protonation site and that the barrier to proton transfer from N3 of 1mC to N7 of 9eG grows dramatically as the base pair begins to dissociate. For the (9eG:1mC)M+; M = Li+, Na+, K+, Rb+, Cs+ complexes, single unique structures could not be assigned. However, the experimental spectra were consistent with the computed spectra. For (9eG:1mC)Li+, the lowest energy structure is one in which Li+ is bound to O6 of 9eG and both O2 and N3 of 1mC; there is also an interbase hydrogen bond from the amine of 1mC to N7 of 9eG. For Na+, K+, and Rb+, similar binding of the metal cation to 1mC is calculated but, unlike Li+, the lowest energy structure is one in which the metal cation is bound to N7 of 9eG; there is also an interbase hydrogen bond between the amine of 1mC and the carbonyl of 9eG. The lowest energy structure for the Cs complex is the Watson-Crick type base pairing with Cs+ binding only to 9eG through O6 and N7 and with three hydrogen bonds between 9eG and 1mC. It also interesting to note that the Watson-Crick base pairing structure gets lower in Gibbs energy relative to the lowest energy complexes as the metal gets larger. This indicates that the smaller, more densely charged cations have a greater propensity to interfere with Watson-Crick base pairing than do the larger, less densely charged metal cations.
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Affiliation(s)
- Ruodi Cheng
- Department of Chemistry, Memorial University, St. John's, NL A1B 3X7, Canada.
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7
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Cheng R, Loire E, Martens J, Fridgen TD. An IRMPD spectroscopic and computational study of protonated guanine-containing mismatched base pairs in the gas phase. Phys Chem Chem Phys 2020; 22:2999-3007. [DOI: 10.1039/c9cp06393e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Infrared multiple photon dissociation spectroscopy has been used to probe the structures of the three protonated base-pair mismatches containing 9-ethylguanine (9eG) in the gas phase. Some of these protonated base-pairs have been identified in RNA.
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Affiliation(s)
- Ruodi Cheng
- Department of Chemistry
- Memorial University
- St. John's
- Canada
| | - Estelle Loire
- Laboratoire Chimie Physique – CLIO
- Campus Universite d’Orsay
- France
| | - Jonathan Martens
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- Nijmegen
- The Netherlands
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8
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Stefan L, Monchaud D. Applications of guanine quartets in nanotechnology and chemical biology. Nat Rev Chem 2019. [DOI: 10.1038/s41570-019-0132-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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9
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Choi YK, Han SY. Facile Production of Hydrogen‐bonded Dimeric Fragments from Collision‐induced Dissociation of Na
+
‐bound G‐Tetrads Predicted by Thermochemistry. B KOREAN CHEM SOC 2019. [DOI: 10.1002/bkcs.11722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Yoon Kyung Choi
- Department of NanochemistryGachon University Seongnam‐si 13120 Republic of Korea
| | - Sang Yun Han
- Department of NanochemistryGachon University Seongnam‐si 13120 Republic of Korea
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10
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Aparicio F, Mayoral MJ, Montoro-García C, González-Rodríguez D. Guidelines for the assembly of hydrogen-bonded macrocycles. Chem Commun (Camb) 2019; 55:7277-7299. [DOI: 10.1039/c9cc03166a] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article highlights selected examples on the synthesis of hydrogen-bonded macrocycles from ditopic molecules and analyze the main factors, often interrelated, that influence the equilibrium between ring and chain species.
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Affiliation(s)
- F. Aparicio
- Nanostructured Molecular Systems and Materials (MSMn) group
- Departamento de Química Orgánica
- Facultad de Ciencias
- Universidad Autónoma de Madrid
- 28049 Madrid
| | - M. J. Mayoral
- Nanostructured Molecular Systems and Materials (MSMn) group
- Departamento de Química Orgánica
- Facultad de Ciencias
- Universidad Autónoma de Madrid
- 28049 Madrid
| | - C. Montoro-García
- Nanostructured Molecular Systems and Materials (MSMn) group
- Departamento de Química Orgánica
- Facultad de Ciencias
- Universidad Autónoma de Madrid
- 28049 Madrid
| | - D. González-Rodríguez
- Nanostructured Molecular Systems and Materials (MSMn) group
- Departamento de Química Orgánica
- Facultad de Ciencias
- Universidad Autónoma de Madrid
- 28049 Madrid
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11
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Azargun M, Meister PJ, Gauld JW, Fridgen TD. The K2(9-ethylguanine)122+ quadruplex is more stable to unimolecular dissociation than the K(9-ethylguanine)8+ quadruplex in the gas phase: a BIRD, energy resolved SORI-CID, IRMPD spectroscopic, and computational study. Phys Chem Chem Phys 2019; 21:15319-15326. [DOI: 10.1039/c9cp01651a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combination of experimental trapped-ion mass spectrometric studies and computational chemistry has been used to assess the intrinsic properties of the potassiated 9-ethylguanine (9eG) self-assembled quadruplex, K2(9eG)122+, in the gas phase.
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Affiliation(s)
- Mohammad Azargun
- Department of Chemistry
- Memorial University of Newfoundland
- St. John's
- Canada
| | - Paul J. Meister
- Department of Chemistry and Biochemistry
- University of Windsor
- Windsor
- Canada
| | - James W. Gauld
- Department of Chemistry and Biochemistry
- University of Windsor
- Windsor
- Canada
| | - Travis D. Fridgen
- Department of Chemistry
- Memorial University of Newfoundland
- St. John's
- Canada
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12
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Villani G. Quantum Mechanical Investigation of the G-Quadruplex Systems of Human Telomere. ACS OMEGA 2018; 3:9934-9944. [PMID: 31459122 PMCID: PMC6644616 DOI: 10.1021/acsomega.8b01678] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/09/2018] [Indexed: 05/17/2023]
Abstract
The three G-quadruplexes involved in the human telomere have been studied with an accurate quantum mechanical approach, and the possibility of reducing them to a simpler model has been tested. The similarities and the differences of these three systems are shown and discussed. Each system has been analyzed through different properties and compared to the others. In particular, we have considered: (1) the shape of the cavity and the atomic charges around it; (2) the electric field in and out of the cavity; (3) the stabilization energy due to the stacking of G-tetrads, to the H-bonds and to the ion interactions; and, finally, (4) to study the mechanism of the process of the ion inclusion in the cavity, the curves of potential energy due to the movement of the Na+ and K+ ions toward the cavity. The results suggest that a detailed study is essential in order to obtain the quantitative properties of these complex systems, but also that some qualitative behaviors can be schematized. Our study makes it clear that the entry of an ion in the cavity of these systems is a complex process, where it is possible to find stable structures with the ion out and in the cavity. Moreover, it is possible that more than one diabatic state is involved in this process.
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Affiliation(s)
- Giovanni Villani
- Istituto di Chimica dei Composti OrganoMetallici, ICCOM—CNR
(UOS Pisa), Area della Ricerca di Pisa, Via G. Moruzzi, 1, I-56124 Pisa, Italy
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13
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Abstract
Minima of the electric field and positions of K+ and Na+ (zero of the x-coordinate is the center of the cavity).
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Affiliation(s)
- Giovanni Villani
- Istituto di Chimica dei Composti OrganoMetallici
- ICCOM – UOS Pisa
- Area della Ricerca del CNR
- I-56124 Pisa
- Italy
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14
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Azargun M, Jami-Alahmadi Y, Fridgen TD. The intrinsic stabilities and structures of alkali metal cationized guanine quadruplexes. Phys Chem Chem Phys 2017; 19:1281-1287. [DOI: 10.1039/c6cp07301h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures and stabilities of self-assembled guanine quadruplexes, M(9eG)8+ (M = Na, K, Rb, Cs; 9eG = 9-ethylguanine), have been studied in the gas phase by blackbody infrared radiative dissociation kinetics to determine the effect the metal cations have on the decomposition energies and reactions of the quadruplex.
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Affiliation(s)
- M. Azargun
- Department of Chemistry
- Memorial University
- St John's
- Canada
| | | | - T. D. Fridgen
- Department of Chemistry
- Memorial University
- St John's
- Canada
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15
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Mayoral MJ, Bilbao N, González‐Rodríguez D. Hydrogen-Bonded Macrocyclic Supramolecular Systems in Solution and on Surfaces. ChemistryOpen 2016; 5:10-32. [PMID: 27308207 PMCID: PMC4906493 DOI: 10.1002/open.201500171] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Indexed: 11/23/2022] Open
Abstract
Cyclization into closed assemblies is the most recurrent approach to realize the noncovalent synthesis of discrete, well-defined nanostructures. This review article particularly focuses on the noncovalent synthesis of monocyclic hydrogen-bonded systems that are self-assembled from a single molecule with two binding-sites. Taking advantage of intramolecular binding events, which are favored with respect to intermolecular binding in solution, can afford quantitative amounts of a given supramolecular species under thermodynamic control. The size of the assembly depends on geometric issues such as the monomer structure and the directionality of the binding interaction, whereas the fidelity achieved relies largely on structural preorganization, low degrees of conformational flexibility, and templating effects. Here, we discuss several examples described in the literature in which cycles of different sizes, from dimers to hexamers, are studied by diverse solution or surface characterization techniques.
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Affiliation(s)
- María J. Mayoral
- Nanostructured Molecular Systems and Materials GroupDepartamento de Química OrgánicaFacultad de CienciasUniversidad Autónoma de Madrid28049MadridSpain
| | - Nerea Bilbao
- Nanostructured Molecular Systems and Materials GroupDepartamento de Química OrgánicaFacultad de CienciasUniversidad Autónoma de Madrid28049MadridSpain
| | - David González‐Rodríguez
- Nanostructured Molecular Systems and Materials GroupDepartamento de Química OrgánicaFacultad de CienciasUniversidad Autónoma de Madrid28049MadridSpain
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16
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Azargun M, Fridgen TD. Guanine tetrads: an IRMPD spectroscopy, energy resolved SORI-CID, and computational study of M(9-ethylguanine)4+ (M = Li, Na, K, Rb, Cs) in the gas phase. Phys Chem Chem Phys 2015; 17:25778-85. [DOI: 10.1039/c5cp00580a] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electrostatic potential map of the neutral guanine tetrad showing the negative hole in the centre.
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