Figure 2.

(a) AFM image of bacteriorhodopsin trimers in their natural lattice formation on a mica substrate. (b) Zero-crossings of Gaussian curvature computed on the scale-space representation of (a) at scale $t={\left(0.6\mathrm{nm}\right)}^2$, overlaid on a brightened version of the image. At this finer scale, individual bacteriorhodopsin monomers are identified. (c) Zero-crossings of Gaussian curvature of the scale-space representation of (a) at the coarser scale $t={\left(1.2\mathrm{nm}\right)}^2$. At larger scales, the trimer structure becomes prevalent.