English: Diagram comparing the presentation of antigens in immunoassays between a typical direct attachment and in a function-spacer-lipid (by analogy to a flower).

Upper image shows the antigen (flower head) presented in a variety of formats directly on a solid surface. The construct attaches randomly to the solid surface.

Lower image shows the same antigen (flower head) presented in optimal orientation as an FSL construct with a spacer (stalk) holding it away from the solid surface. The lipid tail (roots) causes the construct to attach to the solid surface.