FIGURE 4. GMPCPP tubes: comparison with and conversion into microtubules.
From the following article:
Nucleotide-dependent bending flexibility of tubulin regulates microtubule assembly
Hong-Wei Wang and Eva Nogales
Nature 435, 911-915 (16 June 2005)
doi:10.1038/nature03606
a, GMPCPP tube (yellow) and microtubule (green). The side view illustrates radial bending (blue arrow); the end-on view shows how the lateral contact that results in the closure of microtubules is maintained within a protofilament pair but is displaced between pairs (red dashed arrow on inset). b, Direct conversion of GMPCPP tubes into microtubules at 37 °C revealed by negative-stain electron microscopy. Scale bar, 100 nm. c, Fluorescence microscopy of microtubules formed by mixing two populations of differentially labelled GMPCPP tubes before warming the solution, proving that conversion does not involve a depolymerization step. Scale bar, 10 
m.
