FIGURE 3.

LC-MS/MS analysis of C, velia MGDG and DGDG molecular species. A, total lipid extracts of C. velia were analyzed by positive ion LC-MS/MS in neutral loss scanning mode. Neutral loss scanning for m/z 179 (loss of hexose) identified parent ions at m/z 840.3 and 794.3 corresponding to MGDG [M + NH₄]⁺ molecular species with 36:5 and 40:10 (total carbon length/degree of unsaturation) fatty acyl chains, respectively (arrows). B, MS/MS of these parent ions gave fragment ions containing the diacylglycerol ([DAG (40:10) + H]⁺ at m/z 661.3 or [DAG(36:5) + H]⁺ at m/z 615.4) and the monoacylglycerol ([MAG (20:5) + H − H₂O]⁺ at m/z 359 and/or 16:0 MAG [MAG (16:0) + H − H₂O]⁺ at m/z 313) moieties. C, DGDG species were detected by neutral loss scanning for m/z 341 in positive ion mode. Parent ions at m/z 956.1 and 1002.2 corresponded to [M + NH4]⁺ ion of DGDG molecular species with 36:5 and 40:10 acyl chains, respectively (arrow). D, MS/MS of the DGDG parent ions gave fragment ions containing the same diacylglycerol and monoacyl species as in MGDG.