**Fig. 4.** Size and geometric variation of HIV-1 cores. The histograms show the distribution of length (**A**), diameter (**B**) and angle at the narrow end (**C**) of conical HIV-1 cores. Length and diameter were measured once for each core, while the mean of three independent measurements was used in case of the angle. Particles were excluded if the standard deviation of three measurements for the cone angle was >15% of the respective mean, or if all three parameters could not be measured. Arbitrary size classes were defined for each parameter, and the frequency of cores found for each class was plotted. (**D**) A tabulated version of the results. Abbreviations: *n*, number; µ, mean; min., minimal value; max., maximal value; σ, standard deviation; µ_{3σ}, µ_{2σ} or µ_{1σ}, mean calculated from the fraction of particles within the range of three (*n* = 256), two (*n* = 239) or one (*n* = 145) standard deviation of the overall mean, respectively. The correlation between the width at the broad end of the core and the overall length is shown in (**E**). The slope of the line corresponded to an included angle of 19.7 ± 2°.

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