Hi Rongjin, During the SAXS experiment, have you noticed X-ray induced damage on your samples that could explain this?
If you are characterizing your protein in solution you may also be able to pinpoint conformational flexibility using other techniques. - analytical sedimentation. since you have a structure you can calculate the sedimentation coefficient (with SOLPRO) and using sedimentation velocity experiment ( this only takes a few hours) see if it fits your prediction. An unfolded protein or a rigid rod certainly display very different hydrodynamic behaviors (the RASMB mailing list could give you a lot of advice if you want to go this way) - circular dichroism - melting point using differential scanning calorimetry (if you have access to one of those instruments) may be give you some hints about the conformational "variability' of your protein in solution - proteolysis in solution, if your protein is so floppy you would expect it to be rather sensitive to some proteases in solution? my guess is that by now you would have observed this during your purification. - NMR? Hope this helps, All the best -- Pascal F. Egea, PhD Assistant Professor UCLA, David Geffen School of Medicine Department of Biological Chemistry 314 Biomedical Sciences Research Building office (310)-983-3515 lab (310)-983-3516 email pe...@mednet.ucla.edu
