I am refining a structure with a resolution of 2.1 Angstroem using Phenix. The spacegroup is P 31 2 1 (No. 152) with a twin fraction of 0.37 and twin law -h,-k,l. In the refinement procedure the NCS (4 chains) constraints are on, using individual sites, ADP and occupancy refinement. In the last refinement step, I use the option to optimize the values for wxu_scale and wxc_scale. These values are optimizes to 0 for wxc_scale and close to 0 for wxu_scale (0.2) When I tried this at earlier refinement stages wxu_scale was also here optimized in some refinement macrocycles to 0. Interestingly I obtain better R values (0.1948/0.2184), than without the optimization by using the default values (0.1391/0.2438 Rwork/Rfree). In addition to that the statistics are better: clashscore 14.41 (compared to 25.73 without wxc_scale & wxu_scale optimization), rotamer outliers 2.33% (compared o 4.66%) and Ramachandran favoured (Molprobity). How is it possible that wxu_scale and wxc_scale can be optimized to 0 by having better statistics? The total refinement target is defined as Etotal= wxc_scale x wxc x Exray + wc x Egeom As I understand it, the crystallographic refinement target (Exray) would now not be considered in the refinement procedure. Would this refinement procedure be valid? And how is wxc (output of target weights: x-ray data) defined? Thank you very much for your help Michaela Here is the output belonging to the optimization: Refinement Macrocycle 1 of 3 ========================== Target weights: x-ray data ========================= |-----------------------------------------------------------------------------| | XYZ refinement: T = Eexperimental * wxc * wxc_scale + Echem * wc | | wxc = 1.649809 wxc_scale = 0.500 wc = 1.000 | | angle between x-ray and geometry gradient vectors: 93.128 (deg) | | | | ADP refinement: T = Eexperimental * wxu * wxu_scale + Eadp * wu | | wxc = 0.888942 wxc_scale = 1.000 wc = 1.000 | | angle between Xray and ADP gradient vectors: 85.407 (deg) | |-----------------------------------------------------------------------------| ================================ xyz refinement =============================== Start r_free = 0.2118 scale= 0.0000 total_weight= 0.0000 r_free= 0.2181 0 scale= 1.0000 total_weight= 1.6498 r_free= 0.2336 0 scale= 1.5000 total_weight= 2.4747 r_free= 0.2379 1 scale= 2.0000 total_weight= 3.2996 r_free= 0.2412 2 scale= 0.6667 total_weight= 1.0999 r_free= 0.2297 0 scale= 0.5000 total_weight= 0.8249 r_free= 0.2245 1 scale= 0.4000 total_weight= 0.6599 r_free= 0.2226 2 Best r_free = 0.2181 ================================ ADP refinement =============================== ----------Individual ADP refinement---------- Start r_free = 0.2181 scale= 0.0000 total_weight= 0.0000 r_free= 0.2247 0 scale= 1.0000 total_weight= 0.8889 r_free= 0.2262 0 scale= 1.5000 total_weight= 1.3334 r_free= 0.2293 1 scale= 2.0000 total_weight= 1.7779 r_free= 0.2310 2 scale= 0.6667 total_weight= 0.5926 r_free= 0.2236 0 scale= 0.5000 total_weight= 0.4445 r_free= 0.2221 0 scale= 0.4000 total_weight= 0.3556 r_free= 0.2208 0 scale= 0.3333 total_weight= 0.2963 r_free= 0.2203 0 scale= 0.2857 total_weight= 0.2540 r_free= 0.2195 0 scale= 0.2500 total_weight= 0.2222 r_free= 0.2191 0 scale= 0.2222 total_weight= 0.1975 r_free= 0.2186 0 scale= 0.2000 total_weight= 0.1778 r_free= 0.2183 0 Best r_free = 0.2183 Refinement Macrocycle 2 of 3 ========================== Target weights: x-ray data ========================= |-----------------------------------------------------------------------------| | XYZ refinement: T = Eexperimental * wxc * wxc_scale + Echem * wc | | wxc = 1.737535 wxc_scale = 0.500 wc = 1.000 | | angle between x-ray and geometry gradient vectors: 89.612 (deg) | | | | ADP refinement: T = Eexperimental * wxu * wxu_scale + Eadp * wu | | wxc = 0.228155 wxc_scale = 1.000 wc = 1.000 | | angle between Xray and ADP gradient vectors: 155.392 (deg) | |-----------------------------------------------------------------------------| ================================ xyz refinement =============================== Start r_free = 0.2179 scale= 0.0000 total_weight= 0.0000 r_free= 0.2223 0 scale= 1.0000 total_weight= 1.7375 r_free= 0.2272 0 scale= 1.5000 total_weight= 2.6063 r_free= 0.2310 1 scale= 2.0000 total_weight= 3.4751 r_free= 0.2332 2 scale= 0.6667 total_weight= 1.1584 r_free= 0.2267 0 scale= 0.5000 total_weight= 0.8688 r_free= 0.2258 1 scale= 0.4000 total_weight= 0.6950 r_free= 0.2269 2 Best r_free = 0.2223 ================================ ADP refinement =============================== ----------Individual ADP refinement---------- Start r_free = 0.2223 scale= 0.0000 total_weight= 0.0000 r_free= 0.2228 0 scale= 1.0000 total_weight= 0.2282 r_free= 0.2235 0 scale= 1.5000 total_weight= 0.3422 r_free= 0.2256 1 scale= 2.0000 total_weight= 0.4563 r_free= 0.2275 2 scale= 0.6667 total_weight= 0.1521 r_free= 0.2219 0 scale= 0.5000 total_weight= 0.1141 r_free= 0.2213 0 scale= 0.4000 total_weight= 0.0913 r_free= 0.2207 0 scale= 0.3333 total_weight= 0.0761 r_free= 0.2204 0 scale= 0.2857 total_weight= 0.0652 r_free= 0.2201 0 scale= 0.2500 total_weight= 0.0570 r_free= 0.2197 0 scale= 0.2222 total_weight= 0.0507 r_free= 0.2195 0 scale= 0.2000 total_weight= 0.0456 r_free= 0.2194 0 Best r_free = 0.2194 Macrocycle 2 of 3 ========================== Target weights: x-ray data ========================= |-----------------------------------------------------------------------------| | XYZ refinement: T = Eexperimental * wxc * wxc_scale + Echem * wc | | wxc = 2.157676 wxc_scale = 0.500 wc = 1.000 | | angle between x-ray and geometry gradient vectors: 93.409 (deg) | | | | ADP refinement: T = Eexperimental * wxu * wxu_scale + Eadp * wu | | wxc = 0.228399 wxc_scale = 1.000 wc = 1.000 | | angle between Xray and ADP gradient vectors: 140.390 (deg) | |-----------------------------------------------------------------------------| ================================ xyz refinement =============================== Start r_free = 0.2163 scale= 0.0000 total_weight= 0.0000 r_free= 0.2189 0 scale= 1.0000 total_weight= 2.1577 r_free= 0.2299 0 scale= 1.5000 total_weight= 3.2365 r_free= 0.2340 1 scale= 2.0000 total_weight= 4.3154 r_free= 0.2341 2 scale= 0.6667 total_weight= 1.4385 r_free= 0.2282 0 scale= 0.5000 total_weight= 1.0788 r_free= 0.2255 1 scale= 0.4000 total_weight= 0.8631 r_free= 0.2249 2 Best r_free = 0.2189 ================================ ADP refinement =============================== ----------Individual ADP refinement---------- Start r_free = 0.2189 scale= 0.0000 total_weight= 0.0000 r_free= 0.2218 0 scale= 1.0000 total_weight= 0.2284 r_free= 0.2231 0 scale= 1.5000 total_weight= 0.3426 r_free= 0.2250 1 scale= 2.0000 total_weight= 0.4568 r_free= 0.2272 2 scale= 0.6667 total_weight= 0.1523 r_free= 0.2215 0 scale= 0.5000 total_weight= 0.1142 r_free= 0.2209 0 scale= 0.4000 total_weight= 0.0914 r_free= 0.2201 0 scale= 0.3333 total_weight= 0.0761 r_free= 0.2197 0 scale= 0.2857 total_weight= 0.0653 r_free= 0.2195 0 scale= 0.2500 total_weight= 0.0571 r_free= 0.2193 0 scale= 0.2222 total_weight= 0.0508 r_free= 0.2191 0 scale= 0.2000 total_weight= 0.0457 r_free= 0.2190 0 Best r_free = 0.2190 Michaela Kramer PhD student Institute of Biochemistry Winterthurerstrasse 190 8057 Zuerich Switzerland