Parak F, Hartmann H, Schmidt M, Corongiu G, Clementi E
J. Gutenberg-Universität, Institut für Molekulare Biophysik, Mainz, Federal Republic of Germany.
Eur Biophys J. 1992;21(5):313-20. doi: 10.1007/BF00188343.
The space in the unit cell of a metmyoglobin crystal not occupied by myoglobin atoms was filled with water using Monte Carlo calculations. Independent calculations with different amounts of water have been performed. Structure factors were calculated using the water coordinates thus obtained and the known coordinates of the myoglobin atoms. A comparison with experimental structure factors showed that both the low and the high resolution regime could be well reproduced with 814 Monte Carlo water molecules per unit cell with a B-value of 50 A2. The Monte Carlo water molecules yield a smaller standard R-value (0.166) than using a homogeneous electron density for the simulation of the crystal water (R = 0.212). A reciprocal space refinement of the water and the protein coordinates has been performed. Monte Carlo calculations can be used to obtain information for crystallographically invisible parts of the unit cell and yield better coordinates for the visible part in the refinement.
使用蒙特卡罗计算方法，将高铁肌红蛋白晶体晶胞中未被肌红蛋白原子占据的空间用水填充。已针对不同水量进行了独立计算。利用由此获得的水坐标和肌红蛋白原子的已知坐标计算结构因子。与实验结构因子的比较表明，每个晶胞有814个蒙特卡罗水分子且B值为50 Ų时，低分辨率和高分辨率区域均能得到很好的重现。与使用均匀电子密度模拟晶体水（R = 0.212）相比，蒙特卡罗水分子产生的标准R值更小（0.166）。已对水和蛋白质坐标进行了倒易空间精修。蒙特卡罗计算可用于获取晶胞中晶体学不可见部分的信息，并在精修过程中为可见部分提供更好的坐标。
