解像度: 2.2→5 Å / Rfactor Rwork: 0.176 / Rfactor obs: 0.176 / σ(F): 0 詳細: REFINEMENT. THE STARTING MODEL WAS THE ETHYL ISOCYANIDE - HEMOGLOBIN (1HBC) COMPLEX WITH THE LIGAND REMOVED AND THE METHYL ISOCYANIDE LIGAND MODELED INTO INITIAL DIFFERENCE MAP (FO-FC) ...詳細: REFINEMENT. THE STARTING MODEL WAS THE ETHYL ISOCYANIDE - HEMOGLOBIN (1HBC) COMPLEX WITH THE LIGAND REMOVED AND THE METHYL ISOCYANIDE LIGAND MODELED INTO INITIAL DIFFERENCE MAP (FO-FC) ELECTRON DENSITY. THE PROGRAM X-PLOR WAS USED TO ACHIEVE A FINAL CONVENTIONAL R- FACTOR OF 17.6%. THE REFINEMENT PROCESS INCLUDED SIMULATED ANNEALING FOLLOWED BY POSITION AND TEMPERATURE FACTOR REFINEMENT. AN ITERATIVE PROCESS OF MANUAL REFITTING OF SIDE CHAINS AND PLACEMENT OF WATERS WAS PERFORMED UNTIL THE R-FACTOR CONVERGED. THE WEIGHTING OF PSEUDO-ENERGY X-RAY TERM WAS ADJUSTED TO GIVE A BOND RMS OF 0.020 ANGSTROMS IN THE LAST FEW STEPS OF POSITIONAL REFINEMENT. WATERS (N=109) WERE RETAINED FROM THE STARTING STRUCTURE OF OXYHEMOGLOBIN (1HHO). ADDITIONAL WATERS WERE ADDED IF THEY LAY IN 3.5 - 4.O SIGMA PEAKS IN FO-FC ELECTRON DENSITY MAPS AND 1 SIGMA PEAKS IN 2FO-FC MAPS. CONCURRENTLY, A WATER WOULD BE DELETED IF ITS OCCUPANCY (Q) AND TEMPERATURE FACTOR (B) COMBINED TO MAKE THE VALUE (Q*EXP(- B/36)*100%) FALL BELOW 10%. A PEAK NUMBER OF 104 WATERS WAS REACHED. THIS WAS REDUCED TO 66 WATERS OVER THE LAST FEW REFINEMENT CYCLES BY DELETING WATERS WHICH FELL BELOW A 20% THRESHOLD.