Dear members, I am doing a molecular replacement of a transcription factor whose ligand binding structure(24000 Da) is available in PDB but not for the DNA binding(13000 Da). When i am searching for the two copies from ligand binding domain as a template model, i am getting very good solution but i am not getting any density for the DNA binding domain to build up in density. The space gorup is P 1 21 1 (4) and unit cell parameters are Unit Cell: 57.43 69.36 105.99 90.00 90.00 90.00. Please guide me how to get the complete model structure. Table below show the matthews statistics For estimated molecular weight 37000. Nmol/asym Matthews Coeff %solvent P(2.20) P(tot) _____________________________________________________________ 1 5.71 78.46 0.00 0.01 2 2.85 56.91 0.62 0.70 3 1.90 35.37 0.37 0.29 4 1.43 13.82 0.00 0.00 _____________________________________________________________ The phaser molecular replacement gives the following table. istogram of relative frequencies of VM values ---------------------------------------------- Frequency of most common VM value normalized to 1 VM values plotted in increments of 1/VM (0.02) <--- relative frequency ---> 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 | | | | | | | | | | | 10.00 - 8.33 - 7.14 - 6.25 - 5.56 - 5.00 - 4.55 - 4.17 - 3.85 -- 3.57 --- 3.33 ------ 3.12 ---------- 2.94 **************** (COMPOSITION*1) 2.78 ----------------------- 2.63 -------------------------------- 2.50 ----------------------------------------- 2.38 ------------------------------------------------ 2.27 -------------------------------------------------- 2.17 ----------------------------------------------- 2.08 -------------------------------------- 2.00 -------------------------- 1.92 --------------- 1.85 ------- 1.79 --- 1.72 - 1.67 - 1.61 - 1.56 - 1.52 - 1.47 * (COMPOSITION*2) 1.43 - 1.39 - 1.35 - 1.32 - 1.28 - 1.25 - TABLE : Cell Content Analysis: SCATTER :N*Composition vs Probability:0|3x0|1:1,2: $$ N*Composition Probability $$ loggraph $$ 1 0.306066 2 0.00141804 $$ Most probable VM for resolution = 2.27817 Most probable MW of protein in asu for resolution = 92664.2 I have initially indexed the data in C2221 but Rfree was not decreasing so i reindexed the data in data in P121 space group keeping the Rfree flag of C2221. While analysing the symmetry mates , i found large space but no density. structure of Ligand binding domain is almost identical with 90% identity in sequence. I am stuck with this problem and don't know how to process further. I run the phenix.xtriage to evaluate the twining but it suggest no twining. When i reindex from C2221 to P21, the completeness of data reduced from 95 % to 35% whereas the map is very good and Rwork and Rfree are 26/31 for 2.2 resolution. I do not understand why the completeness of data reduced so much on reindexing. please Can anyone explain this phenomenon. Please give me your valuable suggestion. I will appreciate your effort. Thank you