From phasing to structure refinement in-house: Cr/Cu dual-wavelength system and a loopless free crystal-mounting method.

The practical applicability of in-house structure determination using Cr K alpha X-rays (2.29 A) and a loopless free crystal-mounting method was examined using five novel proteins. Proteins from 9.6 to 84 kDa have been solved using this method without any derivatization. In all cases, more than 90% of structures were constructed automatically with side chains by use of the Cr SAD method. The free crystal-mounting technique increases the accuracy of the anomalous differences between Bijvoet mates and makes the in-house single-wavelength SAD method with a Cr K alpha X-ray source a very useful tool for high-throughput structure determination. In addition, a Cr/Cu dual-wavelength system makes it possible to perform structure analysis from phasing to refinement of the structure in-house.