1
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Kulkarni P, Datta D, Ganesh KN. Gemdimethyl Peptide Nucleic Acids (α/β/γ -gdm-PNA): E/Z-Rotamers Influence the Selectivity in the Formation of Parallel/Antiparallel gdm-PNA:DNA/RNA Duplexes. ACS OMEGA 2022; 7:40558-40568. [PMID: 36385799 PMCID: PMC9647847 DOI: 10.1021/acsomega.2c05873] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 10/17/2022] [Indexed: 05/29/2023]
Abstract
Peptide nucleic acids (PNAs) consist of an aminoethylglycine (aeg) backbone to which the nucleobases are linked through a tertiary amide group and bind to complementary DNA/RNA in a sequence-specific manner. The flexible aeg backbone has been the target for several chemical modifications of the PNA to improve its properties such as specificity, solubility, etc. PNA monomers exhibit a mixture of two rotamers (Z/E) arising from the restricted rotation around the tertiary amide N-CO bond. We have recently demonstrated that achiral gemdimethyl substitution at the α, β, and γ sites on the aeg backbone induces exclusive Z (α-gdm)- or E-rotamer (β-gdm) selectivity at the monomer level. It is now shown that γ/β-gdm-PNA:DNA parallel duplexes are more stable than the analogous antiparallel duplexes, while γ/β-gdm-PNA:RNA antiparallel duplexes are more stable than parallel duplexes. Furthermore, the γ/β-gdm-PNA:RNA duplexes are more stable than the γ/β-gdm-PNA:DNA duplexes. These results with γ/β-gdm-PNA are the reverse of those previously seen with α-gdm-PNA oligomers that stabilized antiparallel α-gdm-PNA:DNA duplexes compared to α-gdm-PNA:RNA duplexes. The stability of antiparallel/parallel PNA:DNA/RNA duplexes is correlated with the preference for Z/E-rotamer selectivity in α/β-gdm-PNA monomers, with Z-rotamers (α-gdm) leading to antiparallel duplexes and E-rotamers (β/γ-gdm) leading to parallel duplexes. The results highlight the role and importance of Z- and E-rotamers in controlling the structural preferences of PNA:DNA/RNA duplexes.
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Affiliation(s)
- Pradnya Kulkarni
- Chemistry
Department, Indian Institute of Science
Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati517507, India
| | - Dhrubajyoti Datta
- Chemistry
Department, Indian Institute of Science
Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati517507, India
| | - Krishna N. Ganesh
- Indian
Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune411008, India
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2
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Shiraj A, Ramabhadran RO, Ganesh KN. Aza-PNA: Engineering E-Rotamer Selectivity Directed by Intramolecular H-bonding. Org Lett 2022; 24:7421-7427. [PMID: 36190804 DOI: 10.1021/acs.orglett.2c02993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The replacement of α(CH2) by NH in monomers of standard aeg PNA and its homologue β-ala PNA leads to respective aza-PNA monomers (1 and 2) in which the NαH can form either an 8-membered H-bonded ring with folding of the backbone (DMSO and water) or a 5-membered NαH─αCO (water) to stabilize E-type rotamers. Such aza-PNA oligomers with exclusive E rotamers and intraresidue backbone H-bonding can modulate its DNA/RNA binding and assembling properties.
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Affiliation(s)
- Abdul Shiraj
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr Homi Bhabha Road, Pune 411008, Maharashtra, India
| | - Raghunath O Ramabhadran
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Karkambadi Road, Tirupati 517507, Andhra Pradesh, India
| | - Krishna N Ganesh
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr Homi Bhabha Road, Pune 411008, Maharashtra, India.,Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Karkambadi Road, Tirupati 517507, Andhra Pradesh, India
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3
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Suparpprom C, Vilaivan T. Perspectives on conformationally constrained peptide nucleic acid (PNA): insights into the structural design, properties and applications. RSC Chem Biol 2022; 3:648-697. [PMID: 35755191 PMCID: PMC9175113 DOI: 10.1039/d2cb00017b] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/17/2022] [Indexed: 11/21/2022] Open
Abstract
Peptide nucleic acid or PNA is a synthetic DNA mimic that contains a sequence of nucleobases attached to a peptide-like backbone derived from N-2-aminoethylglycine. The semi-rigid PNA backbone acts as a scaffold that arranges the nucleobases in a proper orientation and spacing so that they can pair with their complementary bases on another DNA, RNA, or even PNA strand perfectly well through the standard Watson-Crick base-pairing. The electrostatically neutral backbone of PNA contributes to its many unique properties that make PNA an outstanding member of the xeno-nucleic acid family. Not only PNA can recognize its complementary nucleic acid strand with high affinity, but it does so with excellent specificity that surpasses the specificity of natural nucleic acids and their analogs. Nevertheless, there is still room for further improvements of the original PNA in terms of stability and specificity of base-pairing, direction of binding, and selectivity for different types of nucleic acids, among others. This review focuses on attempts towards the rational design of new generation PNAs with superior performance by introducing conformational constraints such as a ring or a chiral substituent in the PNA backbone. A large collection of conformationally rigid PNAs developed during the past three decades are analyzed and compared in terms of molecular design and properties in relation to structural data if available. Applications of selected modified PNA in various areas such as targeting of structured nucleic acid targets, supramolecular scaffold, biosensing and bioimaging, and gene regulation will be highlighted to demonstrate how the conformation constraint can improve the performance of the PNA. Challenges and future of the research in the area of constrained PNA will also be discussed.
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Affiliation(s)
- Chaturong Suparpprom
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Tah-Poe District, Muang Phitsanulok 65000 Thailand
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University Phayathai Road Pathumwan Bangkok 10330 Thailand
| | - Tirayut Vilaivan
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Tah-Poe District, Muang Phitsanulok 65000 Thailand
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University Phayathai Road Pathumwan Bangkok 10330 Thailand
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4
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Munyaradzi O, Rundell S, Bong D. Impact of bPNA Backbone Structural Constraints and Composition on Triplex Hybridization with DNA. Chembiochem 2022; 23:e202100707. [PMID: 35167719 PMCID: PMC9136932 DOI: 10.1002/cbic.202100707] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/18/2022] [Indexed: 11/07/2022]
Abstract
We report herein a study on the impact of bifacial peptide nucleic acid (bPNA) amino acid composition and backbone modification on DNA binding. A series of bPNA backbone variants with identical net charge were synthesized to display either 4 or 6 melamine (M) bases. These bases form thymine-melamine-thymine (TMT) base-triples, resulting in triplex hybrid stem structures with T-rich DNAs. Analyses of 6 M bPNA-DNA hybrids suggested that hybrid stability was linked to amino acid secondary structure propensities, prompting a more detailed study in shorter 4 M bPNAs. We synthesized 4 M bPNAs predisposed to adopt helical secondary structure via helix-turn nucleation in 7-residue bPNAs using double-click covalent stapling. Generally, hybrid stability improved upon stapling, but amino acid composition had a more significant effect. We also pursued an alternative strategy for bPNA structural preorganization by incorporation of residues with strong backbone amide conformational preferences such as 4R- and 4S-fluoroprolines. Notably, these derivatives exhibited an additional improvement in hybrid stability beyond both unsubstituted proline bPNA analogues and the helically patterned bPNAs. Overall, these findings demonstrate the tunability of bPNA-DNA hybrid stability through bPNA backbone structural propensities and amino acid composition.
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Affiliation(s)
- Oliver Munyaradzi
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
| | - Sarah Rundell
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
| | - Dennis Bong
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
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5
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Todkari I, Gupta MK, Ganesh KN. Silver soldering of PNA:DNA duplexes: assembly of a triple duplex from bimodal PNAs with all-C on one face. Chem Commun (Camb) 2022; 58:4083-4086. [PMID: 35266467 DOI: 10.1039/d1cc07297h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DNA:bm-PNA duplexes endowed with all-C on either the t-amide or triazole face and mixed base sequence on the other face can be welded with silver ions through C:Ag+:C connects to give triple duplexes in one complex. The interplay of WC and Ag+-mediated duplexes leads to synergistic stability effects on both duplexes and the complex.
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Affiliation(s)
- Iranna Todkari
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, Maharashtra, India.
| | - Manoj Kumar Gupta
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, Maharashtra, India. .,Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road Road, Tirupati, 517507, Andhra Pradesh, India
| | - Krishna N Ganesh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, Maharashtra, India. .,Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road Road, Tirupati, 517507, Andhra Pradesh, India
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6
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Rundell S, Munyaradzi O, Bong D. Enhanced Triplex Hybridization of DNA and RNA via Syndiotactic Side Chain Presentation in Minimal bPNAs. Biochemistry 2022; 61:85-91. [PMID: 34955016 PMCID: PMC9361178 DOI: 10.1021/acs.biochem.1c00693] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
General design principles for recognition at noncanonical interfaces of DNA and RNA remain elusive. Triplex hybridization of bifacial peptide nucleic acids (bPNAs) with oligo-T/U DNAs and RNAs is a robust recognition platform that can be used to define structure-function relationships in synthetic triplex formation. To this end, a set of minimal (mw < 1 kD) bPNA variants was synthesized to probe the impact of amino acid secondary structural propensity, stereochemistry, and backbone cyclization on hybridization with short, unstructured T-rich DNA and U-rich RNAs. Thermodynamic parameters extracted from optical melting analyses of bPNA variant hybrids indicated that there are two bPNA backbone modifications that significantly improve hybridization: alternating (d, l) configuration in open-chain dipeptides and homochiral dipeptide cyclization to diketopiperazine. Further, binding to DNA is preferred over RNA for all bPNA variants. Thymine-uracil substitutions in DNA substrates revealed that the methyl group of thymine accounts for 71% of ΔΔGDNA-RNA for open-chain bPNAs but only 40% of ΔΔGDNA-RNA for diketopiperazine bPNA, suggesting a greater sensitivity to RNA conformation and more optimized stacking in the cyclic bPNA. Together, these data reveal pressure points for tuning triplex hybridization at the chiral centers of bPNA, backbone conformation, stacking effects at the base triple, and the nucleic acid substrate itself. A structural blueprint for enhancing bPNA targeting of both DNA and RNA substrates includes syndiotactic base presentation (as found in homochiral diketopiperazines and d, l peptides), expansion of base stacking, and further investigation of bPNA backbone preorganization.
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Affiliation(s)
- Sarah Rundell
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, United States
| | - Oliver Munyaradzi
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, United States
| | - Dennis Bong
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, United States
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7
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Bhingardeve P, Jain P, Ganesh KN. Molecular Assembly of Triplex of Duplexes from Homothyminyl-Homocytosinyl Cγ( S/ R)-Bimodal Peptide Nucleic Acids with dA 8/dG 6 and the Cell Permeability of Bimodal Peptide Nucleic Acids. ACS OMEGA 2021; 6:19757-19770. [PMID: 34368563 PMCID: PMC8340421 DOI: 10.1021/acsomega.1c02451] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 07/05/2021] [Indexed: 05/08/2023]
Abstract
Peptide nucleic acids (PNAs) are analogues of DNA with a neutral acyclic polyamide backbone containing nucleobases attached through a t-amide link on repeating units of aminoethylglycine (aeg). They bind to complementary DNA or RNA in a sequence-specific manner to form duplexes with higher stablity than DNA:DNA and DNA:RNA hybrids. We have recently explored a new type of PNA termed bimodal PNA (bm-PNA) designed with two nucleobases per aeg repeating unit of PNA oligomer and attached at Cα or Cγ of each aeg unit through a spacer sidechain. We demonstrated that Cγ-bimodal PNA oligomers with mixed nucleobase sequences bind concurrently two different complementary DNAs, forming double duplexes, one from each t-amide and Cγ face, sharing a common PNA backbone. In such bm-PNA:DNA ternary complexes, the two duplexes show higher thermal stability than individual duplexes. Herein, we show that Cγ(S/R)-bimodal PNAs with homothymines (T8) on a t-amide face and homocytosine (C6) on a Cγ-face form a conjoined pentameric complex consisting of a triplex (bm-PNA-T8)2:dA8 and two duplexes of bm-PNA-C6:dG6. The pentameric complex [dG6:Cγ(S/R)-bm-PNA:dA8:Cγ(S/R)-bm-PNA:dG6] exhibits higher thermal stability than the individual triplex and duplex, with Cγ(S)-bm-PNA complexes being more stable than Cγ(R)-bm-PNA complexes. The conjoined duplexes of Cγ-bimodal PNAs can be used to generate novel higher-order assemblies with DNA and RNA. The Cγ(S/R)-bimodal PNAs are shown to enter MCF7 and NIH 3T3 cells and exhibit low toxicity to cells.
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Affiliation(s)
- Pramod Bhingardeve
- Indian
Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Prashant Jain
- Indian
Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Krishna N. Ganesh
- Indian
Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
- Indian
Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati 517507, India
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8
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Brodyagin N, Katkevics M, Kotikam V, Ryan CA, Rozners E. Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications. Beilstein J Org Chem 2021; 17:1641-1688. [PMID: 34367346 PMCID: PMC8313981 DOI: 10.3762/bjoc.17.116] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 06/28/2021] [Indexed: 12/23/2022] Open
Abstract
Peptide nucleic acid (PNA) is arguably one of the most successful DNA mimics, despite a most dramatic departure from the native structure of DNA. The present review summarizes 30 years of research on PNA's chemistry, optimization of structure and function, applications as probes and diagnostics, and attempts to develop new PNA therapeutics. The discussion starts with a brief review of PNA's binding modes and structural features, followed by the most impactful chemical modifications, PNA enabled assays and diagnostics, and discussion of the current state of development of PNA therapeutics. While many modifications have improved on PNA's binding affinity and specificity, solubility and other biophysical properties, the original PNA is still most frequently used in diagnostic and other in vitro applications. Development of therapeutics and other in vivo applications of PNA has notably lagged behind and is still limited by insufficient bioavailability and difficulties with tissue specific delivery. Relatively high doses are required to overcome poor cellular uptake and endosomal entrapment, which increases the risk of toxicity. These limitations remain unsolved problems waiting for innovative chemistry and biology to unlock the full potential of PNA in biomedical applications.
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Affiliation(s)
- Nikita Brodyagin
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, New York 13902, United States
| | - Martins Katkevics
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV-1006, Latvia
| | - Venubabu Kotikam
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, New York 13902, United States
| | - Christopher A Ryan
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, New York 13902, United States
| | - Eriks Rozners
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, New York 13902, United States
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9
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Liang X, Liu M, Komiyama M. Recognition of Target Site in Various Forms of DNA and RNA by Peptide Nucleic Acid (PNA): From Fundamentals to Practical Applications. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210086] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, P. R. China
| | - Mengqin Liu
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Makoto Komiyama
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
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10
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Sharma A, More SH, Ganesh KN. Electrostatics Favor PNA : DNA Stability over Stereochemistry in Pyrrolidine‐Based Cationic Dual‐Backbone PNA Analogues. European J Org Chem 2021. [DOI: 10.1002/ejoc.202001581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Ashwani Sharma
- Department of Chemistry Indian Institute of Science Education and Research (IISER) Tirupati 517507 India
- Department of Biology Indian Institute of Science Education and Research (IISER) Tirupati 517507 India
| | - Shahaji H. More
- Department of Chemistry Indian Institute of Science Education and Research (IISER) Tirupati 517507 India
| | - Krishna N. Ganesh
- Department of Chemistry Indian Institute of Science Education and Research (IISER) Tirupati 517507 India
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11
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Ditmangklo B, Muangkaew P, Supabowornsathit K, Vilaivan T. Synthesis of Pyrrolidinyl PNA and Its Site-Specific Labeling at Internal Positions by Click Chemistry. Methods Mol Biol 2021; 2105:35-60. [PMID: 32088863 DOI: 10.1007/978-1-0716-0243-0_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pyrrolidinyl PNA with an α-/β-dipeptide backbone consisting of alternating nucleobase-modified D-proline and (1S,2S)-2-aminocyclopentanecarboxylic acid (also known as acpcPNA) is a class of conformationally constrained PNA that shows exceptional DNA hybridization properties including very high specificity and the inability to form self-pairing hybrids. In this chapter, details of the syntheses of acpcPNA as well as its monomers and a protocol for site-specific labeling with a fluorescent dye via click chemistry are reported.
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Affiliation(s)
- Boonsong Ditmangklo
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Penthip Muangkaew
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Kotchakorn Supabowornsathit
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Tirayut Vilaivan
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
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12
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Kulkarni P, Datta D, Ramabhadran RO, Ganesh K. Gem-dimethyl peptide nucleic acid (α/β/γ- gdm-PNA) monomers: synthesis and the role of gdm-substituents in preferential stabilisation of Z/ E-rotamers. Org Biomol Chem 2021; 19:6534-6545. [PMID: 34259296 DOI: 10.1039/d1ob01097b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The flexible backbone of aminoethylglycine (aeg) PNA upon substitution becomes sterically constrained to enable conformational pre-organization for preferential binding to DNA or RNA. The bulky gem-dimethyl (gdm) substituent on carbons adjacent to the t-amide sidechain either at Cα (glycyl) or Cβ/Cγ (aminoethylene) sides may influence the Z/E rotamer ratio arising from a restricted rotation around the t-amide bond. Employing 2D NMR (NOESY), it is shown here that the Cα-gdm-PNA-T monomer exhibits exclusively the Z-rotamer, while the Cβ-gdm-PNA-T monomer shows only the E-rotamer. The unsubstituted aeg-PNA-T and Cγ-gdm-PNA-T monomers display a mixture of Z/E rotamers. The rotamers with t-amide carbonyl pointing towards the gem-dimethyl group always prevailed. The results are supported by computational studies that suggested that the preferred rotamers are the outcome of a net energetic benefit from the stabilising n-π* interactions of carbonyls (amide backbone and t-amide sidechain), and C-HO interactions and the destabilising steric clash of gem-dimethyl groups with the t-amido methylene group. The E-rotamer structure in Cγ-gdm is also characterised by X-ray crystallography. The exclusive E-rotamer for the Cβ-gdm monomer seen in solution here is the first such example among several modified PNA monomers. Since the conformation of the sidechain is important for inducing base stacking and effective base pairing, the exclusive E-rotamer in the Cβ-gdm monomer may have significance in the properties of the derived PNA : DNA/RNA duplexes with all E-rotamers.
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Affiliation(s)
- Pradnya Kulkarni
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Dhrubajyoti Datta
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Raghunath O Ramabhadran
- Chemistry Department and CAMOST, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati 517507, India.
| | - Krishna Ganesh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India and Chemistry Department and CAMOST, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati 517507, India.
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13
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Das A, Pradhan B. Evolution of peptide nucleic acid with modifications of its backbone and application in biotechnology. Chem Biol Drug Des 2020; 97:865-892. [PMID: 33314595 DOI: 10.1111/cbdd.13815] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/17/2020] [Accepted: 12/05/2020] [Indexed: 01/23/2023]
Abstract
Peptide nucleic acids (PNAs) are getting prodigious interest currently in the biomedical and diagnostic field as an extremely powerful tool because of their potentiality to hybridize with natural nucleic acids. Although PNA has strong affinity and sequence specificity to DNA/RNA, there is a considerable ongoing effort to further enhance their special chemical and biological properties for potential application in numerous fields, notably in the field of therapeutics. The toolbox for backbone modified PNAs synthesis has been extended substantially in recent decades, providing a more efficient synthesis of peptides with numerous scaffolds and modifications. This paper reviews the various strategies that have been developed so far for the modification of the PNA backbone, challenging the search for new PNA systems with improved chemical and physical properties lacking in the original aegPNA backbone. The various practical issues and limitations of different PNA systems are also summarized. The focus of this review is on the evolution of PNA by its backbone modification to improve the cellular uptake, sequence specificity, and compatibility of PNA to bind to DNA/RNA. Finally, an insight was also gained into major applications of backbone modified PNAs for the development of biosensors.
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Affiliation(s)
- Anuradha Das
- National Institute of Science Education and Research Bhubaneswar (HBNI), Bhubaneswar, India
| | - Biswaranjan Pradhan
- S. K. Dash Center of Excellence of Biosciences and Engineering & Technology, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
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14
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Gupta MK, Madhanagopal BR, Ganesh KN. Peptide Nucleic Acid with Double Face: Homothymine–Homocytosine Bimodal Cα-PNA (bm-Cα-PNA) Forms a Double Duplex of the bm-PNA2:DNA Triplex. J Org Chem 2020; 86:414-428. [DOI: 10.1021/acs.joc.0c02158] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Manoj Kumar Gupta
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Tirupati 517507, India
| | - Bharath Raj Madhanagopal
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Tirupati 517507, India
| | - Krishna N. Ganesh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Tirupati 517507, India
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15
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Bhingardeve P, Madhanagopal BR, Ganesh KN. Cγ( S/ R)-Bimodal Peptide Nucleic Acids (Cγ- bm-PNA) Form Coupled Double Duplexes by Synchronous Binding to Two Complementary DNA Strands. J Org Chem 2020; 85:13680-13693. [PMID: 32985197 DOI: 10.1021/acs.joc.0c01853] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Peptide nucleic acids (PNAs) are linear equivalents of DNA with a neutral acyclic polyamide backbone that has nucleobases attached via tert-amide link on repeating units of aminoethylglycine. They bind complementary DNA or RNA with sequence specificity to form hybrids that are more stable than the corresponding DNA/RNA self-duplexes. A new type of PNA termed bimodal PNA [Cγ(S/R)-bm-PNA] is designed to have a second nucleobase attached via amide spacer to a side chain at Cγ on the repeating aeg units of PNA oligomer. Cγ-bimodal PNA oligomers that have two nucleobases per aeg unit are demonstrated to concurrently bind two different complementary DNAs, to form duplexes from both tert-amide side and Cγ side. In such PNA:DNA ternary complexes, the two duplexes share a common PNA backbone. The ternary DNA 1:Cγ(S/R)-bm-PNA:DNA 2 complexes exhibit better thermal stability than the isolated duplexes, and the Cγ(S)-bm-PNA duplexes are more stable than Cγ(R)-bm-PNA duplexes. Bimodal PNAs are first examples of PNA analogues that can form DNA2:PNA:DNA1 double duplexes via recognition through natural bases. The conjoined duplexes of Cγ-bimodal PNAs can be used to generate novel higher-level assemblies.
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Affiliation(s)
- Pramod Bhingardeve
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Bharath Raj Madhanagopal
- Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati 517507, India
| | - Krishna N Ganesh
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pune 411008, India.,Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Mangalam, Tirupati 517507, India
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16
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Patel R, Sarma S, Shukla A, Parmar P, Goswami D, Saraf M. Walking through the wonder years of artificial DNA: peptide nucleic acid. Mol Biol Rep 2020; 47:8113-8131. [PMID: 32990905 DOI: 10.1007/s11033-020-05819-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 09/04/2020] [Indexed: 11/26/2022]
Abstract
Peptide Nucleic Acid (PNA) serves as an artificial functional analog of DNA. Being immune to enzymatic degradation and possessing strong affinity towards DNA and RNA, it is an ideal candidate for many medical and biotechnological applications that are of antisense and antigene in nature. PNAs are anticipated to have its application in DNA and RNA detection as well as quantification, to serve as antibacterial and antiviral agents, and silencing gene for developing anticancer strategies. Although, their restricted entry in both eukaryotic and prokaryotic cells limit their applications. In addition, aggregation of PNA in storage containers reduces the quality and quantity of functional PNA that makes it inadequate for their mass production and storage. To overcome these limitations, researchers have modified PNA either by the addition of diverse functional groups at various loci on its backbone, or by synthesizing chimeras with other moieties associated with various delivery agents that aids their entry into the cell. Here, this review article summarizes few of the structural modifications that are performed with PNA, methods used to improve their cellular uptake and shedding light on the applications of PNA in various prospects in biological sciences.
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Affiliation(s)
- Rohit Patel
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Sameera Sarma
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Arpit Shukla
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Paritosh Parmar
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Dweipayan Goswami
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Meenu Saraf
- Department of Microbiology and Biotechnology, Gujarat University, Ahmedabad, Gujarat, 380009, India.
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Gupta MK, Madhanagopal BR, Datta D, Ganesh KN. Structural Design and Synthesis of Bimodal PNA That Simultaneously Binds Two Complementary DNAs To Form Fused Double Duplexes. Org Lett 2020; 22:5255-5260. [PMID: 32551691 DOI: 10.1021/acs.orglett.0c01950] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Bimodal PNAs are new PNA constructs designed to bind two different cDNA sequences synchronously to form double duplexes. They are synthesized on solid phase using sequential coupling and click reaction to introduce a second base in each monomer at Cα via alkyltriazole linker. The ternary bimodal PNA:DNA complexes show stability higher than that of individual duplexes. Bimodal PNAs are appropriate to create higher-order fused nucleic acid assemblies.
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Affiliation(s)
- Manoj Kumar Gupta
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Bharath Raj Madhanagopal
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Tirupati 517507, India
| | - Dhrubajyoti Datta
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India
| | - Krishna N Ganesh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhabha Road, Pune 411008, India.,Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karkambadi Road, Tirupati 517507, India
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18
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Antibacterial Peptide Nucleic Acids-Facts and Perspectives. Molecules 2020; 25:molecules25030559. [PMID: 32012929 PMCID: PMC7038079 DOI: 10.3390/molecules25030559] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 01/20/2020] [Accepted: 01/22/2020] [Indexed: 12/13/2022] Open
Abstract
Antibiotic resistance is an escalating, worldwide problem. Due to excessive use of antibiotics, multidrug-resistant bacteria have become a serious threat and a major global healthcare problem of the 21st century. This fact creates an urgent need for new and effective antimicrobials. The common strategies for antibiotic discovery are based on either modifying existing antibiotics or screening compound libraries, but these strategies have not been successful in recent decades. An alternative approach could be to use gene-specific oligonucleotides, such as peptide nucleic acid (PNA) oligomers, that can specifically target any single pathogen. This approach broadens the range of potential targets to any gene with a known sequence in any bacterium, and could significantly reduce the time required to discover new antimicrobials or their redesign, if resistance arises. We review the potential of PNA as an antibacterial molecule. First, we describe the physicochemical properties of PNA and modifications of the PNA backbone and nucleobases. Second, we review the carriers used to transport PNA to bacterial cells. Furthermore, we discuss the PNA targets in antibacterial studies focusing on antisense PNA targeting bacterial mRNA and rRNA.
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Bartold K, Pietrzyk-Le A, Golebiewska K, Lisowski W, Cauteruccio S, Licandro E, D'Souza F, Kutner W. Oligonucleotide Determination via Peptide Nucleic Acid Macromolecular Imprinting in an Electropolymerized CG-Rich Artificial Oligomer Analogue. ACS APPLIED MATERIALS & INTERFACES 2018; 10:27562-27569. [PMID: 30071156 DOI: 10.1021/acsami.8b09296] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We devised and fabricated a chemosensor for determination of the genetically relevant 5'-GCGGCGGC-3' (G = guanine; C = cytosine) oligonucleotide. For that, we simultaneously electrosynthesized and electrode-immobilized a sequence-defined octakis(2,2'-bithien-5-yl) DNA hybridizing probe using both a "macromolecular imprinting in polymer strategy" and a sequence-programmable peptide nucleic acid (PNA) template. With electrochemical impedance spectroscopy (EIS) and surface plasmon resonance (SPR) transductions under stagnant-solution and flow injection analysis (FIA) conditions, respectively, we determined the above oligonucleotide with 200-pM EIS limit of detection. With its EIS-determined apparent imprinting factor of ∼4.0, the chemosensor was discriminative to both mismatched oligonucleotides and Dulbecco's modified Eagle's medium sample interferences.
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Affiliation(s)
- Katarzyna Bartold
- Institute of Physical Chemistry , Polish Academy of Sciences , Kasprzaka 44/52 , 01-224 Warsaw , Poland
| | - Agnieszka Pietrzyk-Le
- Institute of Physical Chemistry , Polish Academy of Sciences , Kasprzaka 44/52 , 01-224 Warsaw , Poland
| | - Karolina Golebiewska
- Institute of Physical Chemistry , Polish Academy of Sciences , Kasprzaka 44/52 , 01-224 Warsaw , Poland
| | - Wojciech Lisowski
- Institute of Physical Chemistry , Polish Academy of Sciences , Kasprzaka 44/52 , 01-224 Warsaw , Poland
| | - Silvia Cauteruccio
- Department of Chemistry , University of Milan , Via Golgi 19 , I-20133 Milan , Italy
| | - Emanuela Licandro
- Department of Chemistry , University of Milan , Via Golgi 19 , I-20133 Milan , Italy
| | - Francis D'Souza
- Department of Chemistry , University of North Texas , 1155 Union Circle , No. 305070, Denton , Texas 76203-5017 , United States
| | - Wlodzimierz Kutner
- Institute of Physical Chemistry , Polish Academy of Sciences , Kasprzaka 44/52 , 01-224 Warsaw , Poland
- Faculty of Mathematics and Natural Sciences, School of Sciences , Cardinal Stefan Wyszynski University in Warsaw , Wóycickiego 1/3 , 01-938 Warsaw , Poland
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20
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Pansuwan H, Ditmangklo B, Vilaivan C, Jiangchareon B, Pan-In P, Wanichwecharungruang S, Palaga T, Nuanyai T, Suparpprom C, Vilaivan T. Hydrophilic and Cell-Penetrable Pyrrolidinyl Peptide Nucleic Acid via Post-synthetic Modification with Hydrophilic Side Chains. Bioconjug Chem 2017; 28:2284-2292. [PMID: 28704609 DOI: 10.1021/acs.bioconjchem.7b00308] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Peptide nucleic acid (PNA) is a nucleic acid mimic in which the deoxyribose-phosphate was replaced by a peptide-like backbone. The absence of negative charge in the PNA backbone leads to several unique behaviors including a stronger binding and salt independency of the PNA-DNA duplex stability. However, PNA possesses poor aqueous solubility and cannot directly penetrate cell membranes. These are major obstacles that limit in vivo applications of PNA. In previous strategies, the PNA can be conjugated to macromolecular carriers or modified with positively charged side chains such as guanidinium groups to improve the aqueous solubility and cell permeability. In general, a preformed modified PNA monomer was required. In this study, a new approach for post-synthetic modification of PNA backbone with one or more hydrophilic groups was proposed. The PNA used in this study was the conformationally constrained pyrrolidinyl PNA with prolyl-2-aminocyclopentanecarboxylic acid dipeptide backbone (acpcPNA) that shows several advantages over the conventional PNA. The aldehyde modifiers carrying different linkers (alkylene and oligo(ethylene glycol)) and end groups (-OH, -NH2, and guanidinium) were synthesized and attached to the backbone of modified acpcPNA by reductive alkylation. The hybrids between the modified acpcPNAs and DNA exhibited comparable or superior thermal stability with base-pairing specificity similar to those of unmodified acpcPNA. Moreover, the modified apcPNAs also showed the improvement of aqueous solubility (10-20 folds compared to unmodified PNA) and readily penetrate cell membranes without requiring any special delivery agents. This study not only demonstrates the practicality of the proposed post-synthetic modification approach for PNA modification, which could be readily applied to other systems, but also opens up opportunities for using pyrrolidinyl PNA in various applications such as intracellular RNA sensing, specific gene detection, and antisense and antigene therapy.
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Affiliation(s)
- Haruthai Pansuwan
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University , Ta-Po District, Muang, Phitsanulok 65000, Thailand
| | | | | | | | | | | | | | - Thanesuan Nuanyai
- Rajamankala University of Technology Rattanakosin , Wang Klai Kangwon Campus, Huahin, Prachuap Khiri Khan 77110, Thailand
| | - Chaturong Suparpprom
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University , Ta-Po District, Muang, Phitsanulok 65000, Thailand
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21
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Bose T, Banerjee A, Nahar S, Maiti S, Kumar VA. β,γ-Bis-substituted PNA with configurational and conformational switch: preferred binding to cDNA/RNA and cell-uptake studies. Chem Commun (Camb) 2016; 51:7693-6. [PMID: 25848728 DOI: 10.1039/c5cc00891c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
(S,S)- and (R,R)-β,γ-Bis-substituted PNAs were synthesized from the C-2 symmetric vicinal diamine system embedded in 1,4 dihydroxybutane and 1,4-dimethoxybutane scaffolds. (R,R)-β,γ-Bis-methoxymethyl-PNA derived from d-tartaric acid was found to be in the right configuration and conformation to be an excellent mimic of PNA, endowed with superior ability to enter into cells.
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Affiliation(s)
- Tanaya Bose
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Pashan Road, Pune, 411008, India.
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22
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Vilaivan T. Pyrrolidinyl PNA with α/β-Dipeptide Backbone: From Development to Applications. Acc Chem Res 2015; 48:1645-56. [PMID: 26022340 DOI: 10.1021/acs.accounts.5b00080] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The specific pairing between two complementary nucleobases (A·T, C·G) according to the Watson-Crick rules is by no means unique to natural nucleic acids. During the past few decades a number of nucleic acid analogues or mimics have been developed, and peptide nucleic acid (PNA) is one of the most intriguing examples. In addition to forming hybrids with natural DNA/RNA as well as itself with high affinity and specificity, the uncharged peptide-like backbone of PNA confers several unique properties not observed in other classes of nucleic acid analogues. PNA is therefore suited to applications currently performed by conventional oligonucleotides/analogues and others potentially beyond this. In addition, PNA is also interesting in its own right as a new class of oligonucleotide mimics. Unlimited opportunities exist to modify the PNA structure, stimulating the search for new systems with improved properties or additional functionality not present in the original PNA, driving future research and applications of these in nanotechnology and beyond. Although many structural variations of PNA exist, significant improvements to date have been limited to a few constrained derivatives of the privileged N-2-aminoethylglycine PNA scaffold. In this Account, we summarize our contributions in this field: the development of a new family of conformationally constrained pyrrolidinyl PNA having a nonchimeric α/β-dipeptide backbone derived from nucleobase-modified proline and cyclic β-amino acids. The conformational constraints dictated by the pyrrolidine ring and the β-amino acid are essential requirements determining the binding efficiency, as the structure and stereochemistry of the PNA backbone significantly affect its ability to interact with DNA, RNA, and in self-pairing. The modular nature of the dipeptide backbone simplifies the synthesis and allows for rapid structural optimization. Pyrrolidinyl PNA having a (2'R,4'R)-proline/(1S,2S)-2-aminocyclopentanecarboxylic backbone (acpcPNA) binds to DNA with outstanding affinity and sequence specificity. It also binds to RNA in a highly sequence-specific fashion, albeit with lower affinity than to DNA. Additional characteristics include exclusive antiparallel/parallel selectivity and a low tendency for self-hybridization. Modification of the nucleobase or backbone allowing site-specific incorporation of labels and other functions to acpcPNA via click and other conjugation chemistries is possible, generating functional PNAs that are suitable for various applications. DNA sensing and biological applications of acpcPNA have been demonstrated, but these are still in their infancy and the full potential of pyrrolidinyl PNA is yet to be realized. With properties competitive with, and in some aspects superior to, the best PNA technology available to date, pyrrolidinyl PNA offers great promise as a platform system for future elaboration for the fabrication of new functional materials, nanodevices, and next-generation analytical tools.
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Affiliation(s)
- Tirayut Vilaivan
- Organic Synthesis Research
Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330, Thailand
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23
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Moccia M, Adamo MFA, Saviano M. Insights on chiral, backbone modified peptide nucleic acids: Properties and biological activity. ARTIFICIAL DNA, PNA & XNA 2014; 5:e1107176. [PMID: 26752710 PMCID: PMC5329900 DOI: 10.1080/1949095x.2015.1107176] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 10/02/2015] [Accepted: 10/07/2015] [Indexed: 12/14/2022]
Abstract
PNAs are emerging as useful synthetic devices targeting natural miRNAs. In particular 3 classes of structurally modified PNAs analogs are herein described, namely α, β and γ, which differ by their backbone modification. Their mode and binding affinity for natural nucleic acids and their use in medicinal chemistry as potential miRNA binders is discussed.
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Affiliation(s)
- Maria Moccia
- Consiglio Nazionale delle Ricerche-Institute of Cristallography; Bari, Italy
| | - Mauro F A Adamo
- Centre for Synthesis and Chemical Biology (CSCB); Department of Pharmaceutical & Medicinal Chemistry; Royal College of Surgeons in Ireland; Dublin, Ireland
| | - Michele Saviano
- Consiglio Nazionale delle Ricerche-Institute of Cristallography; Bari, Italy
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24
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Vilaivan C, Srisuwannaket C, Ananthanawat C, Suparpprom C, Kawakami J, Yamaguchi Y, Tanaka Y, Vilaivan T. Pyrrolidinyl peptide nucleic acid with α/β-peptide backbone: A conformationally constrained PNA with unusual hybridization properties. ARTIFICIAL DNA, PNA & XNA 2014; 2:50-59. [PMID: 21912727 DOI: 10.4161/adna.2.2.16340] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 06/09/2011] [Accepted: 06/10/2011] [Indexed: 01/17/2023]
Abstract
We describe herein a new conformationally constrained analog of PNA carrying an alternating α/β amino acid backbone consisting of (2'R,4'R)-nucleobase-subtituted proline and (1S,2S)-2-aminocyclopentanecarboxylic acid (acpcPNA). The acpcPNA has been synthesized and evaluated for DNA, RNA and self-pairing properties by thermal denaturation experiments. It can form antiparallel hybrids with complementary DNA with high affinity and sequence specificity. Unlike other PNA systems, the thermal stability of acpcPNA·DNA hybrid is largely independent of G+C contents, and is generally higher than that of acpcPNA·RNA hybrid with the same sequence. Thermodynamic parameters analysis suggest that the A·T base pairs in the acpcPNA·DNA hybrids are enthalpically stabilized over G·C pairs. The acpcPNA also shows a hitherto unreported behavior, namely the inability to form self-pairing hybrids. These unusual properties should make the new acpcPNA a potentially useful candidate for various applications including microarray probes and antigene agents.
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Affiliation(s)
- Chotima Vilaivan
- Organic Synthesis Research Unit; Department of Chemistry; Faculty of Science; Chulalongkorn University; Patumwan, Bangkok, Thailand
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25
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C3'-endo-puckered pyrrolidine containing PNA has favorable geometry for RNA binding: novel ethano locked PNA (ethano-PNA). Bioorg Med Chem 2013; 21:4092-101. [PMID: 23743441 DOI: 10.1016/j.bmc.2013.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/08/2013] [Accepted: 05/09/2013] [Indexed: 11/22/2022]
Abstract
A novel peptide nucleic acid (PNA) analogue is designed with a constraint in the aminoethyl segment of the aegPNA backbone so that the dihedral angle β is restricted within 60-80°, compatible to form PNA:RNA duplexes. The designed monomer is further functionalized with positively charged amino-/guanidino-groups. The appropriately protected monomers were synthesized and incorporated into aegPNA oligomers at predetermined positions and their binding abilities with cDNA and RNA were investigated. A single incorporation of the modified PNA monomer into a 12-mer PNA sequence resulted in stronger binding with complementary RNA over cDNA. No significant changes in the CD signatures of the derived duplexes of modified PNA with complementary RNA were observed.
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26
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Narayanaswamy N, Avinash MB, Govindaraju T. Exploring hydrogen bonding and weak aromatic interactions induced assembly of adenine and thymine functionalised naphthalenediimides. NEW J CHEM 2013. [DOI: 10.1039/c3nj00060e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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27
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Sugiyama T, Kittaka A. Chiral peptide nucleic acids with a substituent in the N-(2-aminoethy)glycine backbone. Molecules 2012; 18:287-310. [PMID: 23271467 PMCID: PMC6269907 DOI: 10.3390/molecules18010287] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 12/19/2012] [Accepted: 12/19/2012] [Indexed: 11/16/2022] Open
Abstract
A peptide nucleic acid (PNA) is a synthetic nucleic acid mimic in which the sugar-phosphate backbone is replaced by a peptide backbone. PNAs hybridize to complementary DNA and RNA with higher affinity and superior sequence selectivity compared to DNA. PNAs are resistant to nucleases and proteases and have a low affinity for proteins. These properties make PNAs an attractive agent for biological and medical applications. To improve the antisense and antigene properties of PNAs, many backbone modifications of PNAs have been explored under the concept of preorganization. This review focuses on chiral PNAs bearing a substituent in the N-(2-aminoethyl)glycine backbone. Syntheses, properties, and applications of chiral PNAs are described.
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Affiliation(s)
- Toru Sugiyama
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
- Author to whom correspondence should be addressed; E-Mail: ; Tel./Fax: +81-3-5465-8743
| | - Atsushi Kittaka
- Faculty of Pharmaceutical Sciences, Teikyo University, Kaga, Itabashi-ku, Tokyo 173-8605, Japan; E-Mail:
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28
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Gourishankar A, Ganesh KN. (α,α-dimethyl)glycyl (dmg) PNAs: achiral PNA analogs that form stronger hybrids with cDNA relative to isosequential RNA. ARTIFICIAL DNA, PNA & XNA 2012; 3:5-13. [PMID: 22679528 PMCID: PMC3368815 DOI: 10.4161/adna.19185] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The design and facile synthesis of sterically constrained new analogs of PNA having gem-dimethyl substitutions on glycine (dmg-PNA-T) is presented. The PNA oligomers [aminoethyl dimethylglycyl (aedmg) and aminopropyl dimethylglycyl (apdmg)] synthesized from the monomers 6 and 12) effected remarkable stabilization of homothyminePNA2:homoadenine DNA/RNA triplexes and mixed base sequence duplexes with target cDNA or RNA. They show a higher binding to DNA relative to that with isosequential RNA. This may be a structural consequence of the sterically rigid gem-dimethyl group, imposing a pre-organized conformation favorable for complex formation with cDNA. The results complement our previous work that had demonstrated that cyclohexanyl-PNAs favor binding with cRNA compared with cDNA and imply that the biophysical and structural properties of PNAs can be directed by introduction of the right rigidity in PNA backbone devoid of chirality. This approach of tweaking selectivity in binding of PNA constructs by installing gem-dimethyl substitution in PNA backbone can be extended to further fine-tuning by similar substitution in the aminoethyl segment as well either individually or in conjunction with present substitution.
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Affiliation(s)
- Aland Gourishankar
- Indian Institute of Science Education and Research, Division of Organic Chemistry, National Chemical Laboratory, Pune, India
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29
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Li P, Zhan C, Zhang S, Ding X, Guo F, He S, Yao J. Alkali metal cations control over nucleophilic substitutions on aromatic fused pyrimidine-2,4-[1H,3H]-diones: towards new PNA monomers. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.08.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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30
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Mansawat W, Vilaivan C, Balázs Á, Aitken DJ, Vilaivan T. Pyrrolidinyl peptide nucleic acid homologues: effect of ring size on hybridization properties. Org Lett 2012; 14:1440-3. [PMID: 22375845 DOI: 10.1021/ol300190u] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effect of ring size of four- to six-membered cyclic β-amino acid on the hybridization properties of pyrrolidinyl peptide nucleic acid with an alternating α/β peptide backbone is reported. The cyclobutane derivatives (acbcPNA) show the highest T(m) and excellent specificity with cDNA and RNA.
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Affiliation(s)
- Woraluk Mansawat
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330, Thailand
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31
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β-PNA: peptide nucleic acid (PNA) with a chiral center at the β-position of the PNA backbone. Bioorg Med Chem Lett 2011; 21:7317-20. [PMID: 22050888 DOI: 10.1016/j.bmcl.2011.10.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 10/04/2011] [Accepted: 10/07/2011] [Indexed: 11/22/2022]
Abstract
Peptide nucleic acid (PNA) monomers with a methyl group at the β-position have been synthesized. The modified monomers were incorporated into PNA oligomers using Fmoc chemistry for solid-phase synthesis. Thermal denaturation and circular dichroism (CD) studies have shown that PNA containing the S-form monomers was well suited to form a hybrid duplex with DNA, whose stability was comparable to that of unmodified PNA-DNA duplex, whereas PNA containing the R-form monomers was not.
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32
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Ngamwiriyawong P, Vilaivan T. Synthesis and nucleic acids binding properties of diastereomeric aminoethylprolyl peptide nucleic acids (aepPNA). NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2011; 30:97-112. [PMID: 21360408 DOI: 10.1080/15257770.2010.547839] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A general synthetic method for Fmoc-protected monomers of all four diastereomeric aminoethyl peptide nucleic acid (aepPNA) has been developed. The key reaction is the coupling of nucleobase-modified proline derivatives and Fmoc-protected aminoacetaldehyde by reductive alkylation. Oligomerization of the aepPNAs up to 10mer was achieved by Fmoc-solid phase peptide synthesis methodology. Preliminary binding studies of these aepPNA oligomers with nucleic acids suggested that the "cis-" homothymine aepPNA decamers with (2'R,4'R) and (2'S,4'S) configurations can bind, albeit with slow kinetics, to their complementary RNA [poly(adenylic acid)] but not to the complementary DNA [poly(deoxyadenylic acid)]. On the other hand, the trans homothymine aepPNA decamers with (2'R,4'S) and (2'S,4'R) configurations failed to form stable hybrid with poly(adenylic acid) and poly(deoxyadenylic acid). No hybrid formation could be observed between a mixed-base (2'R,4'R)-aepPNA decamer with DNA and RNA in both antiparallel and parallel orientations.
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Affiliation(s)
- Patcharee Ngamwiriyawong
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
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De CK, Seidel D. Catalytic enantioselective desymmetrization of meso-diamines: a dual small-molecule catalysis approach. J Am Chem Soc 2011; 133:14538-41. [PMID: 21863902 DOI: 10.1021/ja2060462] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The desymmetrization of meso-diamines was accomplished via enantioselective monobenzoylation facilitated by the cooperative action of two small-molecule catalysts. A chiral acyl-transfer reagent is formed in situ through the interplay of benzoic anhydride, 4-(dimethylamino)pyridine as a nucleophilic catalyst, and a chiral amide-thiourea cocatalyst.
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Affiliation(s)
- Chandra Kanta De
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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Ok T, Lee J, Jung C, Lim J, Park CM, Lee JH, Park HG, Lee HS. GNA/aegPNA chimera loaded with RNA binding preference. Chem Asian J 2011; 6:1996-9. [PMID: 21472996 DOI: 10.1002/asia.201100003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Indexed: 11/12/2022]
Affiliation(s)
- Taedong Ok
- Molecular-Level Interface Research Center, Department of Chemistry, KAIST, Daejeon 305-701, Korea
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DNA-, RNA- and self-pairing properties of a pyrrolidinyl peptide nucleic acid with a (2′R,4′S)-prolyl-(1S,2S)-2-aminocyclopentanecarboxylic acid backbone. Tetrahedron Lett 2010. [DOI: 10.1016/j.tetlet.2010.08.102] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Sharma S, Sonavane UB, Joshi RR. Molecular dynamics simulations of cyclohexyl modified peptide nucleic acids (PNA). J Biomol Struct Dyn 2010; 27:663-76. [PMID: 20085383 DOI: 10.1080/07391102.2010.10508580] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Peptide Nucleic Acids (PNA) that bind sequence specifically to DNA/RNA are of major interest in the field of molecular biology and could form the basis for gene-targeted drugs. Molecular dynamics simulations are aimed to characterize the structural and dynamical features to understand the effect of backbone modification on the structure and dynamics along with the stability of the resulting 10mer complexes of PNA with DNA/RNA. Twelve Molecular Dynamics (MD) simulations of duplexes and triplexes with and without cyclohexyl modification were carried out for 10ns each. The simulations indicate that the cyclohexyl modification with different stereoisomers has influenced all the PNA-DNA/RNA complexes. Modification has added rigidity to backbone by restricting beta to +60 in case of (1R,2S) cyclohexyl PNA and to -60 in case of (1S,2R) cyclohexyl PNA. The results of MD simulations were able to show the backbone rigidification and preference for RNA complexes over DNA due to presence of cyclohexyl ring in the PNA backbone.
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Affiliation(s)
- Smriti Sharma
- Bioinformatics Team, Centre for Development of Advanced Computing, Ganesh Khind, Pune University Campus, Pune - 411007
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Lu XW, Zeng Y, Liu CF. Modulating the hybridization property of PNA with a peptoid-like side chain. Org Lett 2009; 11:2329-32. [PMID: 19438197 DOI: 10.1021/ol900587b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modification on the gamma-N of the PNA backbone yielded a PNA analogue with a peptoid-like side chain. We found that the length of the side chain was important in influencing the hybridization affinity of the modified PNA.
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Affiliation(s)
- Xiao-Wei Lu
- Division of Chemical Biology and Biotechnology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
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Dragulescu-Andrasi A, Rapireddy S, Frezza BM, Gayathri C, Gil RR, Ly DH. A simple gamma-backbone modification preorganizes peptide nucleic acid into a helical structure. J Am Chem Soc 2007; 128:10258-67. [PMID: 16881656 DOI: 10.1021/ja0625576] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Peptide nucleic acid (PNA) is a synthetic analogue of DNA and RNA, developed more than a decade ago in which the naturally occurring sugar phosphate backbone has been replaced by the N-(2-aminoethyl) glycine units. Unlike DNA or RNA in the unhybridized state (single strand) which can adopt a helical structure through base-stacking, although highly flexible, PNA does not have a well-defined conformational folding in solution. Herein, we show that a simple backbone modification at the gamma-position of the N-(2-aminoethyl) glycine unit can transform a randomly folded PNA into a helical structure. Spectroscopic studies showed that helical induction occurs in the C- to N-terminal direction and is sterically driven. This finding has important implication not only on the future design of nucleic acid mimics but also on the design of novel materials, where molecular organization and efficient electronic coupling are desired.
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Affiliation(s)
- Anca Dragulescu-Andrasi
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA
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Englund EA, Appella DH. Gamma-substituted peptide nucleic acids constructed from L-lysine are a versatile scaffold for multifunctional display. Angew Chem Int Ed Engl 2007; 46:1414-8. [PMID: 17133633 DOI: 10.1002/anie.200603483] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Englund E, Appella D. γ-Substituted Peptide Nucleic Acids Constructed fromL-Lysine are a Versatile Scaffold for Multifunctional Display. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200603483] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Vilaivan T, Srisuwannaket C. Hybridization of pyrrolidinyl peptide nucleic acids and DNA: selectivity, base-pairing specificity, and direction of binding. Org Lett 2007; 8:1897-900. [PMID: 16623579 DOI: 10.1021/ol060448q] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[structure: see text] A mixed-base, beta-amino acid containing, pyrrolidinyl peptide nucleic acid (PNA) binds strongly and selectively to complementary DNA in an exclusively antiparallel fashion. The PNA-DNA binding specificity strictly follows the Watson-Crick base-pairing rules.
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Affiliation(s)
- Tirayut Vilaivan
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330, Thailand.
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Govindaraju T, Madhuri V, Kumar VA, Ganesh KN. Cyclohexanyl peptide nucleic acids (chPNAs) for preferential RNA binding: effective tuning of dihedral angle beta in PNAs for DNA/RNA discrimination. J Org Chem 2006; 71:14-21. [PMID: 16388612 DOI: 10.1021/jo051227l] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[structures: see text] A serious drawback of peptide nucleic acids (PNAs) from an application perspective that has not been adequately dealt with is nondiscrimination of identical DNA and RNA sequences. An analysis of the available X-ray and NMR solution structures of PNA complexes with DNA and RNA suggested that it might be possible to rationally impart DNA/RNA duplex binding selectivity by tuning the dihedral angle beta of the flexible ethylenediamine part of the PNA backbone (II) via suitable chemical modifications. Cyclohexanyl PNAs (chPNAs) with beta approximately = 65 degrees were designed on the basis of this rationale. The chPNAs introduced remarkable differences in duplex stabilities among their DNA and RNA complexes, with melting temperatures (deltaTm(RNA-DNA) = +16-50 degrees C) depending on the number of modifications and the stereochemistry. This is a highly significant, exceptional binding selectivity of a mix sequence of PNA to RNA over the same DNA sequence as that seen to date. In contrast, cyclopentanyl PNAs (cpPNAs) with beta approximately = 25 degrees hybridize to DNA/RNA strongly without discrimination because of the ring puckering of the cyclopentane ring. The high affinity of chPNAs to bind to RNA without losing base specificity will have immediate implications in designing improved PNAs for therapeutic and diagnostic applications.
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Affiliation(s)
- T Govindaraju
- Division of Organic Chemistry (Synthesis), National Chemical Laboratory, Pune 411008, India
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Kitagawa O, Matsuo S, Yotsumoto K, Taguchi T. Catalytic Asymmetric Desymmetrization of meso-Diamide Derivatives through Enantioselective N-Allylation with a Chiral π-Allyl Pd Catalyst: Improvement and Reversal of the Enantioselectivity. J Org Chem 2006; 71:2524-7. [PMID: 16526810 DOI: 10.1021/jo052488y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the presence of the Trost ligands-Pd catalysts, N-monoallylation of bis(2,4,6-triisopropylbenzne)sulfonylamides derived from meso-1,2-diamines proceeds with good to excellent enantioselectivity (85-96% ee) to give asymmetric desymmetrization products. Under the same conditions, in the reaction with meso-bistolunesulfonylamide derivatives, reversal of the enantioselectivity is observed.
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Affiliation(s)
- Osamu Kitagawa
- Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
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Lundin KE, Good L, Strömberg R, Gräslund A, Smith CIE. Biological activity and biotechnological aspects of peptide nucleic acid. ADVANCES IN GENETICS 2006; 56:1-51. [PMID: 16735154 DOI: 10.1016/s0065-2660(06)56001-8] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
During the latest decades a number of different nucleic acid analogs containing natural nucleobases on a modified backbone have been synthesized. An example of this is peptide nucleic acid (PNA), a DNA mimic with a noncyclic peptide-like backbone, which was first synthesized in 1991. Owing to its flexible and neutral backbone PNA displays very good hybridization properties also at low-ion concentrations and has subsequently attracted large interest both in biotechnology and biomedicine. Numerous modifications have been made, which could be of value for particular settings. However, the original PNA does so far perform well in many diverse applications. The high biostability makes it interesting for in vivo use, although the very limited diffusion over lipid membranes requires further modifications in order to make it suitable for treatment in eukaryotic cells. The possibility to use this nucleic acid analog for gene regulation and gene editing is discussed. Peptide nucleic acid is now also used for specific genetic detection in a number of diagnostic techniques, as well as for site-specific labeling and hybridization of functional molecules to both DNA and RNA, areas that are also discussed in this chapter.
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Affiliation(s)
- Karin E Lundin
- Department of Laboratory Medicine, Clinical Research Center Karolinska Institutet, Karolinska University Hospital, Huddinge 141 86 Stockholm, Sweden
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Rathinavelan T, Yathindra N. Molecular dynamics structures of peptide nucleic acid x DNA hybrid in the wild-type and mutated alleles of Ki-ras proto-oncogene--stereochemical rationale for the low affinity of PNA in the presence of an AC mismatch. FEBS J 2005; 272:4055-70. [PMID: 16098189 DOI: 10.1111/j.1742-4658.2005.04817.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The low affinity of peptide nucleic acid (PNA) to hybridize with DNA in the presence of a mismatch endows PNA with a high degree of discriminatory capacity that has been exploited in therapeutics for the selective inhibition of the expression of point-mutated genes. To obtain a structural basis for this intriguing property, molecular dynamics simulations are carried out on PNA x DNA duplexes formed at the Ki-ras proto-oncogene, comprising the point-mutated (GAT), and the corresponding wild-type (GGT) codon 12. The designed PNA forms an A...C mismatch with the wild-type sequence and a perfect A...T pair with the point mutated sequence. Results show that large movements in the pyrimidine base of the A...C mismatch cause loss of stacking, especially with its penultimate base, concomitant with a variable mismatch hydrogen bond, including its occasional absence. These, in turn, bring about dynamic water interactions in the vicinity of the mismatch. Enthalpy loss and the disproportionate entropy gain associated with these are implicated as the factors contributing to the increase in free energy and diminished stability of PNA x DNA duplex with the A...C mismatch. Absence of these in the isosequential DNA duplex, notwithstanding the A...C mismatch, is attributed to the differences in topology of PNA x DNA vis-à-vis DNA duplexes. It is speculated that similar effects might be responsible for the reduced stability observed in PNA x DNA duplexes containing other base pair mismatches, and also in mismatch containing PNA x DNA duplexes.
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Affiliation(s)
- Thenmalarchelvi Rathinavelan
- Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai, India Institute of Bioinformatics and Applied Biotechnology, ITPB, Bangalore, India
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