Figure 2. CTF Correction and Identification of Best Quality Images from Tilt Series of GroEL.
Tilt series of GroEL were collected and processed using conventional subvolume averaging (see Experimental Procedures) and the proposed reconstruction strategy.
(A) Zero-tilt exposure from representative tilt series at ~2.3 e−/Å2.
(B) Slice through corresponding tomographic reconstruction (~105 e−/Å2 accumulated dose). Scale bars, 35 nm.
(C) Theoretical CTF curve at 2.5 μm defocus estimated from radially averaged, background-subtracted, 1D power spectrum obtained by periodogram averaging using tiles from the tilt series.
(D) FSC against X-ray model of GroEL of non-CTF corrected conventional subvolume averaging reconstruction from 10,000 GroEL particles and proposed CTF-corrected reconstruction by merging of projection sets.
(E and F) Difference in image quality between successive exposures in the tilt series and its impact on resolution of reconstructions. (E) Average phase residual per exposure in the tilt series plotted as a function of the tilt angle using a two-branch data collection scheme (0° to −45° and 2° to 45°). (F) FSC of reconstructions using first 11 exposures from first branch (0° to −20°) and first ten exposures from second branch (2° to 20°).
See also Figure S1.