Dear Li, In regards to concentration ideally you should do a concentration series and from that perform a zero concentration extrapolation. Typically we've had success with a 1-10 mg/ml series and 1.5-3 s exposures at SSRL but it's going to be dependent on molecular weight. You should monitor your signal to look for any up turn at low resolution that would indicate multi-particle interaction or aggregation. If you have signal in the lower concentration samples and you see this effect in the higher concentration ones then take the sequence to more dilute ones. Advice from the beamline scientist or instrument manufacturer should guide you on typical concentrations and exposure times for the source you plan to use.
We found the review by Putnam, Hammel, Hura, and Tainer entitled "Solution scattering (SAXS) combined with crystallography and computation: defining accurate macromolecular structures, conformations and assemblies in solution" (Q Rev Biophys. 2007 Aug;40(3):191-285) to be very useful for practical information. This is available at http://bl1231.als.lbl.gov/publications/index.php. There is also a good example of what to expect in your data at http://bl1231.als.lbl.gov/saxs_protocols/saxs_data_collection_evaluatio.php which is also in the paper. Cheers, Eddie Edward Snell Ph.D. Assistant Prof. Department of Structural Biology, SUNY Buffalo, Hauptman-Woodward Medical Research Institute 700 Ellicott Street, Buffalo, NY 14203-1102 Phone: (716) 898 8631 Fax: (716) 898 8660 Email: [email protected] Telepathy: 42.2 GHz Heisenberg was probably here! > Dear Li, > > The SIBYLS Beamline web page has useful sample prep information at > http://bl1231.als.lbl.gov/saxs_protocols/index.php. They also have a link > to a very good SAXS review article. > > Cheers, > Angela > > > > > Li Sheng <[email protected]> > Sent by: CCP4 bulletin board <[email protected]> > 04/23/2009 06:19 AM > Please respond to > Li Sheng <[email protected]> > > > To > [email protected] > cc > > Subject > [ccp4bb] protein purity in SAXS > > > > > > > Dear all, > > Is there anyone with experience in small angle x-ray scattering? Could > anyone please tell me the requirements for protein sample purity and > concentration? > Thanx in advance. > > > > Sincerely, > Li > > __________________________________________ > Email:[email protected] > Institute of Biochemistry and Cell Biology > Institutes for Biological Sciences > Chinese Academy of Sciences > 320 Yue-Yang Road, Shanghai 200031, China > Tel: +86-21-5492-1217 > __________________________________________ > >
