18 research outputs found
Collision-Induced Dissociation of Branched Oligosaccharide Ions with Analysis and Calculation of Relative Dissociation Thresholds
Combined Partial Acid Hydrolysis and Electrospray Ionization-Mass Spectrometry for the Structural Determination of Oligosaccharides
Cruciform porphyrin pentamers
Cruciform porphyrin pentamers 15 and 16 are obtained in good yield by acid-catalyzed tetramerization of ZnII-pyrroloporphyrin 14, followed by oxidation with DDQ; pyrroloporphyrins are in turn obtained from the corresponding pyrrolochlorins by Diels-Alder type reactions of porphyrins involving thermal extrusion of sulfur dioxide from a pyrrole-fused 3-sulfolene
Anion Dopant for Oligosaccharides in Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
Top-Down Interrogation of Chemically Modified Oligonucleotides by Negative Electron Transfer and Collision Induced Dissociation
Two
sets of synthetic 21–23mer oligonucleotides with various
types of 2′-position modifications have been studied with tandem
mass spectrometry using ion trap collision-induced dissociation (IT-CID)
and negative electron transfer (NET)-CID. A systematic study has been
conducted to define the limitations of IT-CID in sequencing such 2′-chemically
modified oligonucleotides. We found that IT-CID is sufficient in characterizing
oligonucleotide sequences that do not contain DNA residues, where
high sequence coverage can be achieved by performing IT-CID on multiple
charge states. However, oligonucleotides containing DNA residues gave
limited backbone fragmentation with IT-CID, largely due to dominant
fragmentation at the DNA residue sites. To overcome this limitation,
we employed the negative electron transfer to strip an electron from
the multiply charged oligonucleotide anion. Then, the radical anion
species formed in this reaction can fragment via an alternative radical-directed
dissociation mechanism. Unlike IT-CID, NET-CID mainly generates a
noncomplementary d/w ion series. Furthermore, we found that NET-CID
did not show preferential dissociations at the DNA residue sites and
thus generated higher sequence coverage for the studied oligonucleotide.
Information from NET-CID of different charge states is not fully redundant
such that the examination of multiple charge states can lead to more
extensive sequence confirmation. This work demonstrates that the NET-CID
is a valuable tool to provide high sequence coverage for chemically
modified oligonucleotides, and such detailed characterization can
serve as an important assay to control the quality of therapeutic
oligonucleotides that are produced under the good manufacture practice
(GMP) regulations