Atmospheric pressure matrix‐assisted laser desorption/ionization ion trap mass spectrometry of sulfonic acid derivatized tryptic peptides

Abstract

Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) and ion trap mass spectrometry have been used to study the fragmentation behavior of native peptides and peptide derivatives prepared for de novo sequencing applications. Sulfonic acid derivatized peptides were observed to fragment more extensively and up to 28 times more efficiently than the corresponding native peptides. Tandem mass spectra of native peptides containing aspartic or glutamic acids are dominated by cleavage on the C-terminal side of the acidic residues. This significantly limits the amount of sequence information that can be derived from those compounds. The MS/MS spectra of native tryptic peptides containing oxidized Met residues show extensive loss of CH(3)SOH and little sequence-specific fragmentation. On the other hand, the tandem mass spectra of derivatized peptides containing Asp, Glu and oxidized Met show much more uniform fragmentation along the peptide backbone. The AP-MALDI tandem mass spectra of some derivatized peptides were shown to be qualitatively very similar to the corresponding vacuum MALDI postsource decay mass spectra, which were obtained on a reflector time-of-flight instrument. However, the ion trap mass spectrometer offers several advantages for peptide sequencing relative to current reflector time-of-flight instruments including improved product ion mass measurement accuracy, improved precursor ion selection and MS(n). These latter capabilities were demonstrated with solution digests of model proteins and with in-gel digests of 2D-gel separated proteins.

A case study of de novo sequence analysis of N-sulfonated peptides by MALDI TOF/TOF mass spectrometry

“…Only one peptide, HIQKEDVPSER, showed a slightly more abundant cleavage C-terminal to Asp (y 5 ) after derivatization (Figure 6b). A more uniform y-ion series in the MS/MS of sulfonic acid derivatized tryptic peptides spectra using atmospheric pressure MALDI ion trap MS was also observed by others [48].…”

Peer Reviewed: Sulfonic Acid Derivatives for Peptide Sequencing by MALDI MS.

“…Figure 5a is a MALDI PSD spectrum from a quadratic field reflector TOF instrument, Figures 5b and 5c were obtained on state-of-the-art MALDI TOF/TOF instruments, Figure 5d came from an ion trap-TOF hybrid instrument, Figure 5e was produced by atmospheric pressure MALDI on an ion trap (33), and Figure 5f shows ESI (singly charged derivative) on a Q-TOF mass spectrometer. All six spectra are dominated by a single series of y-type fragment ions.…”

Structural characterization of PEGylated rHuG-CSF and location of PEG attachment sites

“…Different chemical modification of peptides were suggested to enhance peptide signals in MS or to obtain predominantly one type of fragments in PSD or MS/MS in order to achieve higher sequence coverage or even more, to directly allow de novo sequencing [15]. Chemical derivatization of the amino group of peptides usually includes guanidination [16][17][18] and sulfonation [19][20][21][22][23]. Guanidination of -amino group of lysine residue with O-methylisourea converts Lys to more basic homoarginine residue, yielding improved signal intensities in MS spectra.…”