FIGURE 4.
Negative ion ES-MS and ES-MS/MS spectra of the native and reduced glycans released by aq. HF. The glycans recovered from NMR analysis were subjected to negative ion ES-MS analysis (A). The major species are annotated according to their deduced compositions by accurate mass and their MS/MS spectra. The doubly charged ions (z = 2) appear shifted by 1.5 mass units (3 Da) after reduction with NaBD4 (B), whereas the singly charged (z = 1) ions (boxed) do not appear after reduction of the sample. The MS/MS spectra and their annotations (insets) of the doubly charged (z = 2) precursor ions in A at m/z 1044.34, 1035.76, and 808.64 are shown in C, D, and E, respectively. The MS/MS spectrum of precursor ion in B at m/z 1037.29 is shown in F. Black square, d-GlcNAc; black bisected square, 2,3-anhydro-d-GlcNAc; open circle, d-Galp; open circle with f subscript, d-Galf; star, d-Xylp; dark gray triangle, l-Fucp; light gray triangle, d-Rhap. P in a circle indicates phosphate. –OH indicates a reducing terminal sugar, and –OL indicates a deuteride-reduced terminal sugar.