Post-Translational Modification Analysis | Sugar Chain Structural Analysis by MSn

Analysis of Glycopeptides Using Data to MS6

The MSn structural analysis of Asn-linked sugar chains is introduced below.
In the MS/MS spectrum obtained using the [M+Na]+(m/z 1999.8) molecular ion peak in the MS spectrum as the precursor ion, the O,2A6 ion(m/z 1562.6) from cross-ring cleavage exhibits the strongest signal. However, at this stage, few product ions can be detected by MS/MS and adequate sugar chain sequence information cannot be obtained.

Fig. 1 MS and MS/MS Spectra of 10 BP

If an MSn spectrum is obtained using the O,2An ion as the precursor ion, strong signals are expected to be observed for [M-60]+(2,4An ion) and [M-120]+(Bn-1 ion). (See AXIMA QIT Application No. 4.)
Subsequently, sugar chain sequence analysis by MSn was conducted using m/z 1562.6 as the precursor ion.

Fig 2. MSn(MS3 to MS6)spectra of 10 BP

In the MS3 spectrum obtained with the O,2A6 ion (m/z 1562.6) as the precursor ion, the 2,4A6 ion (m/z 1502.6) and B5 ion (m/z 1442.6) can be observed, as expected. Similarly, in the MS4 spectrum obtained with the B5 ion (m/z 1442.6) as the precursor ion, product ions comprising disaccharides to heptasaccharides were detected.
MS5 with m/z 1077.5 and MS6 with m/z 712.3 were further performed to observe monosaccharide ([Hex or GlcNAc + Na]+) signals. Such a procedure can obtain a large amount of sugar chain structural information from MSn spectra.

Samples supplied by Dr. Yasuhiro Kajihara, International Graduate School of Arts and Sciences, Yokohama City University

MALDI-TOF Mass Spectrometry

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