Semi-automated methods for simulation and measurement of amyloid fiber distributions obtained from transmission electron microscopy experiments

Transmission electron microscopy (TEM) is the standard procedure for qualitatively confirming the presence of amyloid fibers in a protein aggregation reaction product. However, extracting quantitative information about the amyloid size distribution from the electron micrographs is a nontrivial problem. Here we describe methods for (i) the simulation of pseudo-TEM images of amyloid fiber distributions having known characteristic properties and (ii) the semi-automated processing of experimental TEM images of amyloid fibers to produce two-dimensional histogram plots reflecting either the distribution of amyloid length and width or, alternatively, the distribution of width and fiber rigidity/persistence. The processing method is fully automatic when the density of fibers on the grid is sufficiently low (such that the adsorbed fibers do not touch) and is semi-automatic (requiring some user decision making) when the fibers are overlapping. Termed “ADM” (for Amyloid Distribution Measurement), the program suite is written in MATLAB code and is available on request from the author.