Dear bb, could anyone please share his/her opinion on following matter; I am refining a 4.4 A protein complex structure which I could solve using MR with the high resolution models of the separate components. I also have another 3.5 A crystal form of the complex. My question is whether or not to rebuild/leave "positionally known" side chains in the 4.4 A structure, because of course 2/3 of the time there is of course no density for it. However, a review of the PDB learnes that almost all models deposited between 4 and 5 A contain full side chains! Personally my opinion is not to include them because a model should be a representation of the information content of the experiment and thus density, but maybe that deviates from the consensus. On a more technical note: until now the trimming procedure has only sporadically led to Fo-Fc 'blobs' in the hydrophobic protein interior; are there proven modifications one has to apply to the bulk solvent model mask to avoid these even more? Thanks a lot for your insights, Jonathan -- Jonathan Elegheert Ph.D. Student Unit for Structural Biology& Biophysics http://www.lprobe.ugent.be/xray.html Lab for Protein Biochemistry and Biomolecular Engineering Department of Biochemistry& Microbiology Ghent University, Belgium e-mail: [email protected]