a, c, Mass spectra of MurJ and FtsW proteins (5 μM) in 0.05% (w/v) LDAO reveal a charge state series consistent with a single monomeric protein MurJ (green) and with some phospholipid binding (orange) to FtsW (red). Theoretical and observed masses for MurJ and FtsW are 56090 Da and 56089 Da, and 47172 Da and 47039 Da respectively. b,d Addition of lipid II (blue) at a final concentration of 5 μM to MurJ and 10 μM to FtsW, respectively, leads to formation of a complex with both proteins. A much greater degree of complex formation is observed for MurJ than FtsW at lower lipid II concentration. We find that lipid II binding does not vary significantly in LDAO concentrations ranging from 0.05 (2×CMC)–0.1% (4×CMC).