Figure 4. Distributions and shape-based differentiation of HA and NA spikes.
A, HA cluster (left); single NA (marked) in a cluster of HAs (center); and cluster of mainly NA spikes (right). B & C, schematic models (left) and tomographic sections of a single HA (B) and NA (C). (D) Model of the distribution of HA (green) and NA (gold) on a single influenza virion. The lipid bilayer is blue. Figure is reprinted from Harris et al., Influenza virus pleiomorphy characterized by cryoelectron tomography, 2006, PNAS 103(50):19123-7, with permission from the National Academy of Sciences of the USA [27]. Bars, 50 nm in A; 5 nm in B & C; 20 nm in D.