(750f) Estimating Insulin Nuclei Concentration From Amyloid Fibrils: A Theoretical Approach

Considerable progress has been made in characterizing amyloid diseases since 1901, when amyloids fibrils were first connected with dementia. More than 20 proteins have been associated with different amyloid diseases, but the connection between amyloidosis and disease is still unclear. Recent contradictory reports suggest that the fibrils and/or the oligomer precursors cause toxicity. Here, we offer a theoretical estimate of nuclei concentrations using a ?reverse estimate? in which fibril lengths are used to back-calculate the concentration of nuclei originally present in solution. Assuming the nucleation model is valid, with a few reasonable assumptions, a fibril length distribution calculated with an atomic force microscope and a set of seeding experiments to show that fibrils with different length elongate with the same rate, we estimated the in vitro concentration of nuclei for the model hormone, recombinant human insulin, to be in the picomolar range. Because of their propensity to form aggregates (non-ordered) and fibrils (ordered), this very low concentration could explain the difficulty in fractionating, isolating and blocking nuclei toxicity.