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Abstract No.: TuP-199
Session: Posttranslational Modifications
Presentation date: Tue, Aug 29, 2006
Presentation time: 09:50 – 11:20

Detection of Peptides Containing Cysteine Sulfonic Acid Using Matrix-Assisted Laser Desorption/Ionization (MALDI) and Laser Desorption on Porous Silicon (DIOS) Mass Spectrometry

Tomoya Kinumi1, Ryuichi Arakawa2, Yasushi Shigeri1, Etsuo Niki1

1 Natl. Inst. of Advanced Industrial Science and Technology /NMIJ, Ikeda, Osaka, Japan
2 Kansai University, Suita, Osaka, Japan

Correspondence address: Tomoya Kinumi, Natl. Inst. of Advanced Industrial Science and Technology, 1-8-31, Ikeda, Osaka, 563-8577 Japan.

Keywords: Ionization, Desorption; Ionization, Matrix-Assisted Laser Desorption; Oxidation; Peptide, Modified.

Novel aspect: Systematic study for effective detection of cysteine sulfonic acid containing peptide by MALDI and DIOS.


Oxidative stress causes large number of diseases by impairing the function of DNA and protein. Under the oxidative stress condition, an active site cystein residue of anti-oxidative enzyme, peroxiredoxin was selectively oxidized to cysteine sulfinic acid and/or sulfonic acid by reducing peroxides. However, it is difficult to analyze oxidized peroxiredoxins and the oxidized peptide by MALDI mass spectrometry, because cysteine sulfonic acid-containing peptides exhibit low response in MALDI. In this study, matrix conditions and the effect of diammonium hydrogencitrate (DAHC) as additive were investigated for the analysis of cysteine sulfonic acid-containing peptides in MALDI and matrix-free ionization method, desorption/ionization on porous silicon (DIOS).
When equimolar three-component mixtures of peptides carrying free cysteine, cysteine sulfonic acid, and carbamidomethyl cysteine were measured by MALDI using α-cyano-4-hydroxycinnamic acid (CHCA), no signal corresponding to cysteine sulfonic acid-containing peptide could be observed due to suppression effect. However, by addition of DAHC to CHCA, the peaks of cysteine sulfonic acid-containing peptides were successfully observed. In the DIOS mass spectra of these analytes, the use of DAHC also enhanced the peak intensity of the cysteine sulfonic acid-containing peptides. Based on studies with these model peptides, tryptic digests of oxidized peroxiredoxin 6 were examined as a complex peptide mixture by MALDI and DIOS. In MALDI, the peaks of cysteine sulfonic acid-containing peptides were observed when using THAP/DAHC as the matrix, but this was not so with CHCA. In DIOS, the signal from cysteine sulfonic acid-containing peptides was suppressed, however, the use of DAHC significantly enhanced the signal intensity with an increase in the number of observed peptides. The results show that DAHC in the matrix or on the DIOS chip decreases discrimination and suppression effects in addition to suppressing alkali-adduct ions, which leads to a beneficial effect to detect peptides containing cysteine sulfonic acid.