Fibre length distributions quantified from negative stain EM micrographs of DpHF18 (top), DpHF19 (middle) and DpHF19_9his (bottom) in pH 8, 6, 5, 4.2, 3.5 and 3 buffer, and after incubation at pH 3 followed by raising the pH to 8. In the box and whisker plots, the centre line is the median, the box represents Q1 to Q3, the lower whisker is Q1–1.5 × IQR and the upper whisker is Q3 + 1.5 × IQR (Q1 is the first quartile, Q3 is the third quartile and IQR is the interquartile range). From left to right, the numbers of independent fibres quantified for DpHF18 are 436, 329, 3, 1, 1, 166; for DpHF19, 61, 1491, 207, 26, 1, 33; and for DpHF19_9his, 427, 522, 26, 1, 2, 9, 155.
