Fig. 2.

EM density map used by Miyazawa, Fujiyoshi, and Unwin (18) to derive a structure of the nAChR TM domain (PDB ID code 1OED, a precursor to the full structure 2BG9). The view is a slice through the TM domain, in the membrane plane, showing regions of high (blue), intermediate (white), and low density (red). Dark-blue circles include protein backbone and most side-chain density; the composition of material filling gaps between α-helices is unspecified but presumed to be water. However, the density in these gaps (white or pale blue) is higher than in the pentameric pore (red) and similar to that of the lipid surrounding the protein. Data retrieved from the Electron Microscopy Database, entry EMD-1044.