Collision-induced Dissociation of Polyprotonated Oligonucleotides Produced by Electrospray Ionization

✍ Scribed by Jinsong Ni; Michael A. A. Mathews; James A. McCloskey

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 177 KB
• Volume: 11
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(199704)11:6<535::aid-rcm898>3.0.co;2-p

✦ Synopsis

The efficient production of polyprotonated oligonucleotides, studied at n ≤ 19, occurs from water/propan-2-ol solutions over an ammonium acetate concentration range between 2.5 and 40 mM and a pH range from 5 to 11. Average charge-state levels observed were approximately half of those found in mass spectra of polyanionic oligonucleotides, reflecting differences in sites of ionization: heterocyclic bases for protonation and phosphodiester backbone for deprotonation. Collision-induced dissociation mass spectra show three principal reaction paths: (1) release of protonated bases, with abundances dictated largely by base proton affinity; (2) phosphodiester chain cleavage at C3' -O3' indicative of sequence in the 3' → 5' direction; and (3) chain cleavage concomitant with base loss giving furan-type ions indicative of sequence in the 5' → 3' direction, analogous to reactions of polyanionic oligonucleotides. Thymine residues undergo very little protonation, resulting in characteristic absence of phosphodiester cleavage on the 3' side of T sites, producing mass-ladder gaps representing dinucleotides.