13/08 – 14h00 – sala 69

Seminar: Restoring high-resolution contrast in images affected by beam-induced motion

Prof. Niko Grigorieff (Brandeis University)

The contrast observed in images of frozen-hydrated biological specimens prepared for electron cryo-microscopy falls significantly short of theoretical predictions. It is widely acknowledged that motion of the specimen during its exposure to the electron beam leads to significant blurring in the recorded images. We have studied the amount and direction of motion of virus particles suspended in thin vitrified ice layers across holes in perforated carbon films using exposure series. Our data shows that the beam induces a drum-like motion in the ice layer, leading to particle rotations of up to a few degrees and shifts of a few 10s of Angstroms. Using a new type of camera, a direct electron detector, we were able to record movies of vitrified specimens while exposed to the electron beam. The movies offer the possibility of frame alignment and averaging to significantly reduce the blurring in the images and restore the high-resolution signal. As an example, I will show how the new movie recording technique enhances the resolution of virus reconstructions.

13^th August 2012, at 2:00 PM

Sala 69 – Andar superior do Prédio Biologia
Campus – Centro Nacional de Pesquisa em Energia e Materiais – CNPEM
Rua Giuseppe M. Scolfaro, 10.000 – Guará
Phone: (19) 3512-1010