Electron microscopy and image processing
Images of 2D crystals of the photostationary state were recorded at liquid nitrogen temperatures using a field emission gun electron microscope operating at 300 kV. The density map was calculated to 5.5 Å resolution using a 0.005 Å-1 sampling of the lattice lines. The table summarises electron crystallographic statistics from the structure determination.
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Electron crystallographic data
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Plane group Cell dimensions a (Å) b (Å) c (Å) |
p22121 58.8 83.7 200.0 (arbitrary) |
| α = β = γ (º) |
90.0 |
| Number of imagesa Range of defocus (Å) |
87 2700 - 14100 |
| Effective resolution of 3D data setb (Å) |
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In-plane Perpendicular to the membrane Average temperature factor (Bxy)c |
5.5 11.7 200 ± 95 |
| Total number of observed amplitudes and phases |
22099 |
| Number of unique structure factors Completeness (%) 0-45º 0-60º 0-90º |
2073 83.2 68.2 59.0 |
| Overall weighted R-factor d (%) |
34.9 |
| Overall weighted phase residual d (º) |
24.0 |
a Twenty-two at 0º, sixteen at 20º, twelve at 35º, twenty-six at 45º and eleven at 60º.
b As calculated from the point-spread function.
c Average temperature factor to scale image amplitudes against bacteriorhodopsin electron diffraction data, correcting for high-resolution image amplitude fall-off.
d From program LATLINEK.