Re: [ccp4bb] Quick-soak

[Matt Vetting]

     We have had really outstanding success using trimethyllead and 
samarium acetate as 'quick soak' derivatives. Both are soluble to 100 mM 
in most crystallization solutions and have large anomalous signals at the 
copper-kalpha wavelength used at most home sources. A quick 30 sec to 5 
minute soak and collect as much data (180-360 degrees) as quickly as 
possible. We have been able to solve many datasets by SAD alone on our 
home source (R-AXIS-IV++ - RUH3R generator). Pb and Sm are bound by acidic 
residues. Post mortum of 'quick soak' datasets made in such a manner 
usually indicate 1-3 strong sites which are usually heavy atoms 
coordinated by more than on acidic group, 3-4 medium occupancy sites, and 
5-10 low occupancy sites. Software such as BnP and PHENIX will readily 
find and phase well collected (high accuracy) 'quick soak' datasets.