Dorset D L
Electron Diffraction Department, Hauptman-Woodward Medical Research Institute, Buffalo, NY 14203-1196, USA.
Acta Crystallogr A. 1998 May 1;54 ( Pt 3):290-5. doi: 10.1107/s0108767397016905.
The crystal structure of orthorhombic bacteriorhodopsin was determined in projection by direct methods from electron diffraction amplitudes, assuming that, after re-scaling the problem, the Fourier transform of projected alpha-helices could be modeled by atomic scattering factors. A basic set comprising two origin-defining phases, two phase values from sigma 1 triple estimates and an algebraic unknown (resolved early in the phase determination) was extended to a total set of 20 terms, with only two errors. Five helix sites were observed in the first potential map and, after three cycles of Fourier refinement, the rest of the asymmetric unit was found. The overall phase accuracy was 47 degrees or 22 degrees for the 25 most intense reflections.
通过直接法从电子衍射振幅确定了正交细菌视紫红质的晶体结构投影，假设在重新缩放问题后，投影α-螺旋的傅里叶变换可以用原子散射因子建模。一个基本集包括两个定义原点的相位、来自σ1三重估计的两个相位值和一个代数未知数（在相位确定早期解决），扩展到总共20个项，只有两个误差。在第一个潜在图中观察到五个螺旋位点，经过三个周期的傅里叶精修后，发现了不对称单元的其余部分。对于25个最强反射，整体相位精度为47度或22度。
