Fig. 3. Purified trypomastigote GPIs are free of lipopeptides. A sample of 10 pmol of synthetic Mycoplasma lipopeptide (A) and 10 pmol of purified T.cruzi trypomastigote mucin GPI fraction (B) were analysed by positive-ion MALDI-TOF under identical conditions. The absence of ions in (B) reflects the absence of any lipopeptides or peptides in the preparation and the inability of GPIs to produce positive ions under the conditions used. In (A), the ions at m/z 2136, 2158 and 2180 are the [M+H]⁺, [M+Na]⁺ and [M–H+2Na]⁺ ions of S–(2,3–bishexa- decanoyloxypropyl)cysteine-GNNDESNISFKEK, respectively and the minor ion at m/z 2152* is most probably the [M+H]⁺ ion of the corresponding sulfoxide. The ions at lower m/z values may be due to degradation products.