Hi Jessica, If you see spots and they fit a lattice, you should use them. Use the b=10 solution in P1 that you have with 3 models (or two if one is iffy) and use that as a start model for MR in b=20 and start searching for the rest. Alternatively, use the b=10 model with stuff that looks decent and generate a model for b=20 by adding in the lattice translations. This can be tricky, especially when you are not in P1, so perhaps try the first option first.
Pseudo translational symmetry will do this to you btw: https://journals.iucr.org/d/issues/2008/01/00/ba5111/ba5111.pdf , section 3.4.2 Regards Peter On Wed, May 27, 2020 at 7:00 PM Jessica Bruhn < 0000450e5de75376-dmarc-requ...@jiscmail.ac.uk> wrote: > Hello, > > I am wondering if pseudosymmetry can cause weak reflections that mimic the > doubling of one unit cell axis' length. Has anyone seen something like this > before? > > I am processing data from a small molecule sample collected with electron > diffraction from multiple crystals. For the b axis, it is not clear if the > length should be 10A or 20A. There are spots with the correct spacing for > b=20A, but every other spot seems weaker than the spots along k if I choose > b=10A (this extends beyond (0,k,0)). I am unable to phase the b=20 data. I > have solved this structure in P1 with b=10 and found four molecules in the > ASU and in P212121 with b=10 resulting in one molecule in the ASU. In P1, > three of the four molecules adopt the same conformation, but the fourth > molecule is in an alternate conformation that causes only ~1/2 of the > molecule to be consistent with the first three. In P212121 I see density > for part of this alternative conformation, but the full molecule in this > alternate conformation cannot pack properly in P212121. Based on these > results and some orthogonal data, I think I should refine the solution in > P1 with b=10. Does it seem reasonable that pseudosymmetry is causing these > weak reflections along k hinting at a doubling of the b axis? > > Thanks in advance! > > Best, > Jessica > > -- > Jessica Bruhn, Ph.D > Principal Scientist > NanoImaging Services, Inc. > 4940 Carroll Canyon Road, Suite 115 > San Diego, CA 92121 > Phone #: (888) 675-8261 > www.nanoimagingservices.com > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > -- ------------------------------------------------------------------------ P.H. Zwart Staff Scientist Molecular Biophysics and Integrated Bioimaging & Center for Advanced Mathematics for Energy Research Applications Lawrence Berkeley National Laboratories 1 Cyclotron Road, Berkeley, CA-94703, USA Cell: 510 289 9246 PHENIX: http://www.phenix-online.org CAMERA: http://camera.lbl.gov/ ------------------------------------------------------------------------- ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
