Figure 1.

(a) AFM image of membrane protein SecYEG embedded in a lipid bilayer supported on a glass substrate¹¹. (b) Particles from (a) with increased color contrast, and their corresponding scale-space signature to their right. The response of $\det {\mathscr{H}}_{norm}L$ scaled by a factor of 1 × 10¹⁹ was calculated at the central pixel in each particle and plotted as a function of the effective scale⁴⁴ approximated as ${\log }_2(1+t)$. Top Row: A smaller particle and the corresponding scale extracted from the scale-space signature, marked by red dashed line. Middle Row: A larger particle, with a detected scale greater than the top particle. Bottom Row: A complex particle with substructure components. Two scales are identified, one corresponding to a smaller substructure component and one for the particle as a whole. (c) The 90 strongest scale-space extrema of ${\nabla }_{norm}^{2}L$, represented as circles centered on the spatial coordinates of the scale-space extremum with radius $\sqrt{2t}$. As in the style used by Lindeberg²⁹, red circles represent maxima (dark blobs), blue represent minima (bright blobs). (d) The 90 strongest scale-space maxima of $\det {\mathscr{H}}_{norm}L$, also as circles with radius $\sqrt{2t}$. Both positive and negative blobs correspond to maxima of $\det {\mathscr{H}}_{norm}L$.