PMC

CID spectra for triply deprotonated molecular ions of Arixtra®. a) CID of [M-3H]³⁻ showing that a low charge state leads to the loss of SO₃ and little useful structural information. b) Deprotonation of eight acidic groups, equal to the number of sulfo groups, through Na⁺/H⁺ exchange and charging, reduces SO₃ loss but provides few useful fragments. c) When all ten acidic groups are deprotonated, a large number of structurally informative glycosidic and cross-ring cleavages are observed.

Annotated structures showing observed cleavages for Arixtra for two different charge states and levels of sodiation. Both [M-10H+6Na]⁴⁻ and [M-10H+5Na]⁵⁻ show similar fragmentation patterns affording more comprehensive structural information. The numbers adjacent to a cleavage indicate the number of sodium ions present in the fragment ion, open circles denote SO₃ loss accompanying the indicated fragmentation, and filled circles denote loss of 2 or more SO₃ groups. Colored lines indicate isobaric cleavages, for example ^2,4X₄ and ^1,5A₄, shown in red, have the same elemental composition, and are indistinguishable by mass measurement.