Duplex formation and secondary structure of γ-PNA observed by NMR and CD.
Peptide nucleic acids (PNAs) are non-natural oligonucleotides mimics, wherein the phosphoribose backbone has been replaced by a peptidic moiety (N-(2-aminoethyl)glycine). This peptidic backbone lends itself to substitution and the γ-position has proven to yield oligomers with enhanced hybridization properties. In this study, we use Nuclear Magnetic Resonance (NMR) and Circular Dichroism (CD) to explore the properties of the supramolecular duplexes formed by these species. We show that standard Watson-Crick base pair as well as non-standard ones are formed in solution. The duplexes thus formed present marked melting transition temperatures substantially higher than their nucleic acid homologs. Moreover, the presence of a chiral group on the γ-peptidic backbone increases further this transition temperature, leading to very stable duplexes. PNA duplexes with a chiral backbone present a marked chiral secondary structure, observed by CD, and showing a common folding pattern for all studied structures. Nevertheless small differences are observed depending on the details of the nucleobase sequence.
Strasbourg University, Plateforme d'Analyse Chimique de Strasbourg Illkirch, 74 route du Rhin 67401 Illkirch, France.
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JM
Viéville
Department of Organic Chemistry, University of Geneva, Geneva CH1211, Switzerland.
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S
Barluenga
Department of Organic Chemistry, University of Geneva, Geneva CH1211, Switzerland.
N
N
Winssinger
IGBMC, CNRS UMR 7104, 1 rue Laurent Fries BP10142, 67404 Illkirch France. Electronic address: delsuc@igbmc.fr.
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MA
Delsuc
D002942:Circular Dichroism / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D020135:Peptide Nucleic Acids / Q000737:chemistry*; D017433:Protein Structure, Secondary
D020135:Peptide Nucleic Acids
Circular dichroism; Imino proton; NMR spectroscopy; Secondary structure; γ-PNA