FIGURE 2.
TAG profiles of purified cottonseed lipid droplets analyzed by DOMS. a, representative positive ion, high resolution TAG profile of purified LDs from mature cotton embryos (cv. Coker 312). Dominant TAG species are identified as ammonium adducts [M + NH4]+ with peaks labeled according to the three fatty acids present in each TAG molecular species as identified through subsequent tandem MS analysis by collision induced dissociation (CID). b, schematic of tandem MS of a TAG with acyl chains R1, R2, R3. Fragmentation of the R1 ester bond (blue line) produces a corresponding DAG plus hydrogen adduct (blue, R2 and R3) and free fatty acid (FFA) plus ammonia (blue, R1). c, confirmation of acyl chain composition by tandem MS detects the diagnostic DAG product ions minus a free fatty acid compared with known masses (34). DAGs represented in multiple TAGs shown are only labeled once for clarity. sn-positioning of each acyl chain was not determined. P, 16:0-palmitic acid; O, 18:1-oleic acid; L, 18:2-linoleic acid.