Hi, I cannot really answer what the lowest resolution for MR is but I have been successful with 4 A data for a protein-DNA complex and so I encourage you to try your 3.6 A data set. Of course, it also depends on the quality of your data, in particular how well/how many low resolution reflections were measured, solvent content and your search model.
In my case, I have used only protein as the search model (45% of the molar mass was missing) to reduce model bias and to avoid trouble with different DNA conformations (deviating from ideal B-DNA). The obtained MR solution gave a correct packing (for protein) with a lot of space for DNA. The resulting electron density map showed clear density for protein but it was very noisy apart from that. I have used density modification (solvent flipping) in CNS to increase the contrast of the map and it brought out a signal for DNA (solvent content was 65%). As Raji pointed out, have a look for the phosphate backbone or some density in a helical arrangement. Most probably, you will not be able to resolve individual bases. Good luck, christian Muthiah wrote: > What is the lowest resolution one can try to do molecular replacement > with? I have a 3.6 angstroms resolution data for a protein-DNA complex > and wondering whether I can try MR to see the density for DNA. _______________________________________________________________________ Dr. Christian Biertümpfel Laboratory of Molecular Biology NIDDK/National Institutes of Health phone: +1 301 402 4647 9000 Rockville Pike, Bldg. 5, Rm. B1-03 fax: +1 301 496 0201 Bethesda, MD 20892-0580 USA _______________________________________________________________________
