Open AccessSingle-molecule orientation localization microscopy for resolving structural heterogeneities between amyloid fibrils
Author(s) -
Tianben Ding,
Tingting Wu,
Hesam Mazidi,
Oumeng Zhang,
Matthew D. Lew
Publication year - 2020
Publication title -
optica
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 5.074
H-Index - 107
ISSN - 2334-2536
DOI - 10.1364/optica.388157
Subject(s) - orientation (vector space) , molecule , microscopy , dipole , materials science , chemistry , crystallography , physics , optics , mathematics , geometry , organic chemistry
Simultaneous measurements of single-molecule positions and orientations provide critical insight into a variety of biological and chemical processes. Various engineered point spread functions (PSFs) have been introduced for measuring the orientation and rotational diffusion of dipole-like emitters, but the widely used Cramér-Rao bound (CRB) only evaluates performance for one specific orientation at a time. Here, we report a performance metric, termed variance upper bound (VUB), that yields a global maximum CRB for all possible molecular orientations, thereby enabling the measurement performance of any PSF to be computed efficiently (~1000× faster than calculating average CRB). Our VUB reveals that the simple polarized standard PSF provides robust and precise orientation measurements if emitters are near a refractive index interface. Using this PSF, we measure the orientations and positions of Nile red (NR) molecules transiently bound to amyloid aggregates. Our super-resolved images reveal the main binding mode of NR on amyloid fiber surfaces, as well as structural heterogeneities along amyloid fibrillar networks, that cannot be resolved by single-molecule localization alone.