DENV-2 NGC strain used for the cryoEM reconstructions was propagated in mosquito C6/36 cells. Virus was purified by precipitation with 40% PEG 8000 and then ultracentrifugation onto a 25% sucrose cushion. Virus was further purified by banding on a 10%-30% potassium tartrate gradient. The virus band was removed and dialyzed against 12 mM Tris pH 8.0, 120 mM NaCl, 1 mM EDTA, and concentrated using a Millipore Centricon filter. Purified virus was mixed with 1OAN or DN57opt at a concentration of 1 molecule of peptide for every E protein on the surface of the virus. The complex was incubated for half an hour at 37uC followed by half an hour at 4uC and then flash frozen on holey carbon grids in liquid ethane. Images of the frozen complex were taken with a Philips CM200 FEG transmission electron microscope (Philips, Eindhoven, The Netherlands) at a magnification 51,040 using an electron dose of approximately, 25e-/Å 2 using a Charge-Couple device.