Nanopore measurements. a Intact VLP (green) sonicated VLP (blue) and 217 nm polystyrene beads (pink). b VLP after sonication and passage through a 0.45 µm (red) or 0.8/0.2 µm (cyan) filter. c The calculated particle size distribution of filtered VLP samples after calibration using the polystyrene beads. d Pressure dependence of the particle flow rate. Calibration beads (green triangles), sonicated and filtered (0.45 μm) VLP (blue circles). R2 was 0.99 for both linear regressions.