a.).Tandem MS of lyase resistant tetrasaccharide [1,1,2,4,1] by nanospray ionization. The insets show expansions of m/z regions showing the four deuterated forms corresponding to the product ions indicated. The Y ions in the insets are labeled with a letter that corresponds to a structure shown to the right. ; b.) distribution of isotopically labeled product ions from the lyase resistant tetrasaccharide of composition [1,1,2,4,1]4-; c.) distribution of isotopically labeled product ions from the lyase resistant tetrasaccharide of composition [1,1,2,3,1]4-; d.) representations of structures present in [1,1,2,3,1] tandem mass spectrum.