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. 1998 Jun 23;95(13):7299–7304. doi: 10.1073/pnas.95.13.7299

Figure 4.

Figure 4

Circularly averaged radial density profiles for the most rounded PR− MuLV (a) and WT MuLV (b) displayed in Fig. 3. The locations of the membrane envelope (E), the track pattern (T), and the inner track pattern (IT) are indicated. The lipid bilayer envelope (E) has a constant distance between the phosphate head groups (peak-to-peak distance 37.5 ± 3.3 Å; n = 8) for both particles, but the inner leaflet seems to have a lower density in the PR− MuLV compared with the WT MuLV. We attribute the shoulder of density on the inner leaflet of the bilayer to the region occupied by the matrix protein (M), which has a thickness of 40 ± 9 Å. The track region (T) corresponds to the outer surface of the core and is not well defined in the WT MuLV particles. For the PR− MuLV, there was considerable variation in the lucent region between the track and matrix regions (43 ± 16 Å, n = 4). Consequently, the radial location of the track pattern varies from particle to particle.