Fig. 1: Negative stain EM visualizes one or two LCAT molecules preferentially bound to HDL.

a The LCAT–HDL complex is separated from excess free LCAT and HDL via SEC. The peak of the complex was then imaged. The shoulder after the complex peak corresponds to free HDL. b A raw micrograph of negative stain EM showing individual particles of the LCAT–HDL complex. Pink circles show particles with 2:1 LCAT:HDL. The scale bar is 20 nm. c, d Selected class averages (left) and a 3D reconstruction (right) of particles revealing 1:1 (c) and 2:1 (d) LCAT:HDL stoichiometry. No side views are shown for the 2:1 complex as they would be similar to side views for a 1:1 complex. The black scale bar for the 2D classes is 10 nm and for the 3D models it equals 5 nm. See Supplementary Fig. 1 for all class averages.