Surface Force Measurements. Surface force measurements were carried out with a Mark III instrument, and the spring constant used was 205 N/m. In surface force measurements between oriented monolayers of DC-SIGNR and 5 mol % Man 9 GlcNAc 2 containing lipid monolayers ( Figure 1C ), the separation distance D between the lipid bilayers can be determined within (0.1 nm by interferometry. 25 The difference in the total thickness, T, of the molecular assembly relative to contact between supporting DPPE monolayers was measured after the deposition of the outer lipid layers. The absolute membrane 26 where T NTA-TRIG-DLGE is the thickness of the NTA-TRIG-DLGE monolayer 27 and T DTPC is the thickness of the DTPC on the neoglycolipid-containing membrane. The DTPC layer thickness does not include the thickness of the Man 9 GlcNAc 2 headgroup, such that D = 0 is defined as contact between the NTA-TRIG-DLGE and bare DTPC membranes.