β-CTT alters the structure of the microtubule plus end. β-CTT alters the structure of the microtubule plus end. (A) Representative image of a microtubule assembled from the untreated tubulin (6.9 μM). Dashed white line is the coverage of the line scan across the microtubule with intensities plotted in (C). Scale bar = 1 μm. (B) Same as (A) assembled with S-tubulin (4.0 μM). (C) Intensity measurements plotted as a function of pixel position of the microtubules in (A) (black) and (B) (red). (D) Mean tip SD plotted as a function of polymerization rate for tubulin (black) and S-tubulin (red). N = 355 time points per polymerization rate, from at least five different microtubules. Data points are mean ± 95% CI plotted for each concentration. Colby P Fees, and Jeffrey K Moore LSA 2018;1:e201800054 © 2018 Fees and Moore