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Tandem mass spectrometry sequencing in the negative ion mode to read binary information encoded in sequence‐defined poly(alkoxyamine amide)s
Author(s) -
Charles Laurence,
Laure Chloé,
Lutz JeanFrançois,
Roy Raj Kumar
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7413
Subject(s) - chemistry , moiety , deprotonation , tandem mass spectrometry , amide , dissociation (chemistry) , homolysis , mass spectrometry , nitroxide mediated radical polymerization , electrospray ionization , photochemistry , radical , ion , stereochemistry , organic chemistry , radical polymerization , monomer , polymer , chromatography
Rationale Digitally encoded oligomers composed of two distinct amide coding units spaced by a nitroxide moiety were recently decrypted using a tandem mass spectrometry (MS/MS) sequencing approach developed for protonated oligomers. Here, the MS/MS behavior of deprotonated oligomers was explored in the negative ion mode to provide both structural and mechanistic complementary information. Methods Binary‐encoded oligo(alkoxyamine)amides, containing coding 0 / 1 amide units spaced by a TEMPO nitroxide moiety, were ionized in negative ion mode electrospray thanks to their α end‐group containing a carboxylic acid function. Deprotonated molecules were subjected to collision‐induced dissociation in MS/MS and MS 3 experiments, combined with accurate mass measurements, for a thorough investigation of their dissociation behavior. Results Deprotonated oligomers readily dissociated upon collisional activation via competitive homolytic cleavages of all fragile alkoxyamine linkages between any coding 0 or 1 monomers and a nitroxide moiety. As expected, only product ions holding the deprotonated α end‐group were detected while complementary moieties containing the ω termination were released as radicals. The so‐formed distonic radical anions were observed to further depolymerize according to a radical‐induced process, as evidenced by MS 3 experiments. Conclusions Messages encoded in oligo(alkoxyamine)amides were readily decrypted by MS/MS sequencing performed in the negative ion mode. When compared with results obtained in positive ion mode ESI‐MS/MS, these data provided further evidence regarding the influence of adducted proton on the charge‐remote homolytic cleavage of alkoxyamine linkages. Copyright © 2015 John Wiley & Sons, Ltd.