Linkage between doublets 1 and 2 when the 1-2 bridge is present in a cross section. (a, c, and e) The 1-2 bridge (8-nm period) in the xy plane (a), xz plane (c), and tilted section along the linkage (e). (b and d) The other two dominant linkages in the cross section (b) and tilted section along the two dominant linkages (d) are shown. The yellow crosses in b and c and e indicate the same position as the yellow crosses in a and d, respectively. Yellow lines in a and d indicate the planes of sections in b and c and e, respectively. The black arrowhead in b indicates the region where the inner bridge is discontinued. (f) Longitudinal section showing IDA of wild-type doublet 1 in the region of the 1-2 bridge. The blue arrowhead points to the difference from doublet 1 structure outside the 1-2 bridge region (Fig. 1 h). Bar, 20 nm.