Comparison of the SMALP lipid profiles of the three purified E. coli membrane proteins: ZipA, FtsA, and PgpB. The phospholipid compositions are either shown as sum for each of the three classes (a), or as individual molecular species under PE (b), PG (c) or CL (d). All phospholipid species were confirmed and assigned by tandem MS in negative ion mode. Data points for ZipA and FtsA correspond to three biological replicates, while PgpB corresponds to three technical replicates. Error bars represent ± S.D. Significant differences (upon one-way ANOVA) are denoted as *(p < 0.05), **(p < 0.01), or ***(p < 0.001).