IUCr activities

Was the SDPD round robin drug biased?

The preliminary conclusions of the first Structure Determination by Powder Diffractometry Round Robin (SDPDRR) were given at ECM-18,Prague, Aug. 1998. The Web site had 800 visitors and 70 data downloads were counted, 31 participants were explicit about the software they used. Only four final participants sent questionnaires of which none determined the inorganic compound structure [Co(NH3)5CO3]NO3•H2O, and only two produced the pharmaceutical compound structure C22H24N2O8•HC1 (tetracycline hydrochloride). One success was due to the ability of DRUID software to locate a molecule inside a cell by a “Global Optimization Method”. The second success made use of the good old Patterson approach, but some additional materials, not provided by the Round Robin organizers, are suspected to have played an important role. Namely five cigarettes and two cups of coffee, as IUCr Commission News confessed by the participant, who solved the structure in 3 (very probably intense) hours. The conclusion of this Round Robin is that SDPD is not yet routine. Solving structures “on demand” by powder diffractometry requires not only good software but also some user skills. This is why crystallography is still so exciting. We should not forget the contribution of the human brain and its stimulation by the quasi drugs like caffeine and nicotine. Both structures were also solved by the organizers, with the help of caffeine. Jokes aside, one reason for so few successes could be the lack of availability of some recent packages in the public domain, particularly software allowing the location of molecular fragments in cells.

Detailed information is available at http://fluo.univlemans.fr:8001/SDPDRR/.

Armel Le Bail and Lachlan Cranswick