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Charge dependent behavior of PNA/DNA/PNA triplexes in the gas phase
Author(s) -
Delvolvé Alice,
Tabet JeanClaude,
Bregant Sarah,
Afonso Carlos,
Burlina Fabienne,
Fournier Françoise
Publication year - 2006
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1124
Subject(s) - chemistry , dna , non covalent interactions , covalent bond , nucleobase , base pair , electrospray ionization , crystallography , stereochemistry , molecule , ion , hydrogen bond , organic chemistry , biochemistry
Intact noncovalent complexes were studied in the gas phase using negative ion nano‐ESI mass spectrometry. Among various noncovalent systems studied in the gas phase, the interaction of DNA strands with peptide nucleic acids (PNAs) presents a strong interest as biologically relevant systems. PNAs originally described by Nielsen are used as DNA mimics as possible medical agents by imprisoning DNA single strands into stable noncovalent complexes. Two types of PNAs were investigated in the PNA/DNA multiplex: the original Nielsen's PNA and a modified backbone PNA by the introduction of syn ‐ and anti ‐(aminoehtyl)thiazolidine rings. We first investigated the stoichiometry of PNA/DNA multiplexes formed in solution and observed them in the gas phase via qualitative kinetics of complementary strand associations. It resulted in observing PNA 2 /DNA triplexes (ts) as the multiply deprotonated species, most stable in both the solution and gas phase. Second, charge‐dependant decompositions of these species were undertaken under low‐energy collision conditions. It appears that covalent bond cleavages (base releasing or skeleton cleavage) occur from lower ts charge states rather than ts unzipping, which takes place from higher charge states. This behavior can be explained by considering the presence of zwitterions depending on the charge state. They result in strong salt‐bridge interactions between the positively charged PNA side chain and the negatively charged DNA backbone. We propose a general model to clearly display the involved patterns in the noncovalent triplex decompositions. Third, the relative stability of three PNA 2 /DNA complexes was scrutinized in the gas phase by acquiring the breakdown curves of their ts 6− form, corresponding to the ts unzipping. The chemical structures of the studied PNAs were chosen in order to evidence the possible influence of backbone stereochemistry on the rigidity of PNA 2 /DNA complexes. It provided significantly different stabilities via V m measurements. The relative gas‐phase stability order obtained was compared to that found in solution by Chassaing et al. , and shows qualitative agreement. Copyright © 2006 John Wiley & Sons, Ltd.

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