TABLE 3.
Characteristics of membrane-bound arraysa
| Unit cell dimensions |
| His-MoCANC |
| a = b = 77.2 ± 2.6 Å |
| γ = 118.6 ± 2.3° |
| His-MoCANCexact |
| a = b = 76.5 ± 1.4 Å |
| γ = 120.4 ± 0.9° |
| His-MoCANC plus RNA |
| a = b = 77.0 ± 1.5 Å |
| γ = 120.1 ± 0° |
| Space group determination |
| His-MoCANC phase residuals |
| p1 = 25.4 ± 3.5° |
| p2 = 25.8 ± 6.0° |
| p3 = 16.1 ± 5.9° |
| p6 = 18.1 ± 5.6° |
| Merge statistics |
| His-MoCANC |
| p1 phase residual = 13.6 ± 4.1° |
| p1 R factor = 0.96 ± 0.04 |
| p6 phase residual = 16.5 ± 6.7° |
| p6 R factor = 0.86 ± 0.18 |
| His-MoCANCexact |
| p1 phase residual = 18.6 ± 3.8° |
| His-MoCANC plus RNA |
| p1 phase residual = 34.0 ± 5.4° |
2D His-MoCANC arrays were formed on PC plus Ni+2-DHGN monolayers and stained, photographed, and digitized as described in Materials and Methods. Ten His-MoCANC images were Fourier transformed and viewed as power spectra to permit indexing of diffraction patterns, from which real-space unit cell dimensions are derived. For space group determinations, CTF-corrected, unbent aph files from indexed transforms were used in conjunction with the MRC program ALLSPACE to obtain averaged phase residuals to 20-Å resolution, where 0° represents perfect agreement with a designated space group while a 90° value is indicative of random agreement. Note that the average numbers of comparisons used for p1, p2, p3, and p6 calculations were 23, 12, 17, and 47, respectively, and no other space groups gave phase residuals of less than 30°. Merging of aph files to 20-Å resolution was performed with the program origtiltc for the p1 merge and origtiltb for the p6 merge. Average phase residuals for both merges derive from an average of 11 comparisons per aph file. Average R factors represent vector-averaged amplitude values divided by the corresponding scalar sum of amplitudes for each reflection. R-factor values for random data depend on the number of vectors averaged and correspond to values of 0.41 and 0.23 for the p1 and p6 merges, respectively. Note that while His-MoCANCexact and His-MoCANC+RNA arrays generally gave lower-quality crystals than did His-MoCANC, seven His-MoCANCexact and two His-MoCANC+RNA images also were examined. The His-MoCANCexact images yielded a unit cell size of a = b = 76.5 ± 1.4 Å, γ = 120.4 ± 0.9°, and gave an average phase residual of 18.6 ± 3.8° in a p1 merge to His-MoCANC images. The His-MoCANC+RNA images gave cell parameters of a = b = 77.0 ± 1.5 Å, γ = 120.1 ± 0°, and merged with His-MoCANC files to a phase residual of 34.0 ± 5.4°.