Low-dose phase retrieval of biological specimens using cryo-electron ptychography

Abstract

Cryo-electron microscopy is an essential tool for high-resolution structural studies of biological systems. This method relies on the use of phase contrast imaging at high defocus to improve information transfer at low spatial frequencies at the expense of higher spatial frequencies. Here we demonstrate that electron ptychography can recover the phase of the specimen with continuous information transfer across a wide range of the spatial frequency spectrum, with improved transfer at lower spatial frequencies, and as such is more efficient for phase recovery than conventional phase contrast imaging. We further show that the method can be used to study frozen-hydrated specimens of rotavirus double-layered particles and HIV-1 virus-like particles under low-dose conditions (5.7 e/Å 2) and heterogeneous objects in an Adenovirus-infected cell over large fields of view (1.14 × 1.14 μm), thus making it suitable for studies of many biologically important structures.

CryoET structures of immature HIV Gag reveal six-helix bundle

“…Radial density profiles from three different particles of similar size displayed three distinct peaks corresponding to the CA NTD , CA CTD and NC-RNA density layers (Fig. 4a ) 38 . While CA NTD , CA CTD and SP1 are rigidly connected as seen in the Gag ΔMA T8I map, NC-RNA is flexibly linked to SP1, resulting in a smeared density in Gag ΔMA T8I subtomogram averages (Fig.…”

CryoET structures of immature HIV Gag reveal a complete six-helix bundle and stabilizing small molecules distinct from IP6

“…Radial density profiles from three different particles of similar size displayed three distinct peaks corresponding to the CA NTD , CA CTD and NC-RNA density layers (Fig. 4a) 37 . While CA NTD , CA CTD and SP1 are rigidly connected as seen in the Gag ΔMA T8I map, NC-RNA is flexibly linked to SP1, resulting in a smeared density in Gag ΔMA T8I subtomogram averages (Fig.…”

Advances in the electron diffraction characterization of atomic clusters and nanoparticles

“…Electron diffraction methods at low dose configurations is another alternative to obtain the crystallography of biological and sensitive samples. Another methodology is the phase retrieval in electron holography at low doses as a systematic approach to reduce electron beam current in the sample [27][28][29] . Detection is a very important aspect in low dose radiation and illumination cannot be visualized with the binoculars using low doses.…”