MAPT and red-green color blindness: Because cryoEM resolves only the very rigid residues in cross-ß-structure at high resolution and has reported additional unidentified electron density in tau fibrils, the analysis suggests that in vitro-generated 2N4R fibrils, but not heparin-induced fibrils, have a similar core length as tau fibrils purified from CBD patient brain (residues ~274 to ~380 were resolved at high resolution; PDB code: 6TJO; marked in light blue in Fig. 2e).