Typing of Leishmania lipophosphoglycans by electrospray mass spectrometry

A method has been developed to identify the repeating phosphosaccharide uni ts of Leishmania lipophosphoglycans using electrospray mass-spectrometry (E S-MS). Cone voltage-induced fragmentation of intact lipophosphoglycan was f ound to be as effective as analysis of mild acid hydrolysates in identifyin g the degree of modification of the repeating units of lipophosphoglycans d erived from Leishmnnia mexicana and Leishmania,major. This finding was expl oited in a 'rapid-analysis' method in which a crude organic extract of simi lar to 2 x 10(9) L. major promastigote cells was loaded onto a reverse-phas e cartridge for immediate elution into the mass-spectrometer. Using this ap proach, it was possible to identify the repeating units by total ion scanni ng and scanning for parents of the m/z 79 (PO3-) fragment ion. This approac h is suitable for quick-typing of lipophosphoglycan repeats and was shown t o detect alterations in repeat side chains caused by: (1) culturing L. majo r promastigotes in the presence of L-fucose; and (2) in vitro metacyclogene sis of L. major promastigotes. It is anticipated that the method will be ap plicable to small samples of cultured field isolates or genetically-manipul ated strains. (C) 1999 Elsevier Science B.V. All rights reserved.