High-resolution electrospray mass spectra of hexaethylene glycol connected biotinylated HNK-1 antigenic trisaccharide molecular probe and its non-sulfated analogue.

High-resolution electrospray mass spectra in positive and negative ion modes (MS and MS/MS) were measured and described for biotinylated hexaethylene glycol (HEG) connected molecular probes bearing HNK-1 (abbreviation of human natural killer cell-1 epitope) antigenic trisaccharide (1) and its non-sulfated analogue (2). For molecular probe 2, in its CID MS/MS of [M+2Na](2+), unexpected peak at m/z 530.2475 [C22H41N3O8SNa](+) was observed and attributed to the fragmentation of the aglycone at the end of the HEG chain distant from the biotin fragment. No homologous ions having the difference C2H4O smaller than that one were observed. The same cleavage was revealed in negative ion spectra. A similar fragmentation was found for other non-sulfated, biotinylated HEG-spacered molecular probes thus demonstrates this type of fragmentation characteristic for such glycosides.