Tiancen, I am not entirely clear - are you asking for techniques that can improve your *existing* material - or are you shopping for *any* technique that will eventually result in an improvement?
If you're looking for the latter, and are willing to send me your protein sequence (I promise to keep it confidential, of course) - I can supply you with a list of changes you can do on the level of sequence modification, with fairly high likelihood of success (tested on a number of bad proteins to-date, with very high success ratio). I cannot disclose the algorithms used to calculate these mutations but they're not the same as Derewenda's surface entropy method (which also works) or some of the existing servers dedicated to the same purpose. If it helps, you can look at my recent short blurb for other ideas :) http://www.xtals.org/pdfs/rescue_crystals.pdf Artem > Dear all, > > Sorry for the non-CCP4 question. I think this is an old story but our > knowledge to deal with it is very limited. So any suggestions will be > greatly appreciated. > > We have crystallized a 21KD protein with 2 disulfide bonds grown for one > month in 0.1M tri-sodium citrate pH 5.6, 0.5M (NH4)2SO4 and 1M Li2SO4. The > crystals look big (~0.4mm x 0.4mm x 0.3mm) and pretty (sharp edge, clean > surface) but diffracted to only 4A in-house. The spots are quite strong > and isotropic at low resolution but decay sharply beyond 5-6A. The crystal > belongs to P4 pointgroup (P422 is also possible) with cell parameters of > 127.6, 127.6, 162.5, 90, 90, 90. The solutions we can think of to elevate > its diffraction ability are as follows: > > 1) Try synchrotron radiation > 2) Try a lot of similar crystals and hope one of them diffracts better > than others > 3) Let the crystals grow for a longer time and hope it could pack more > ¡°orderly¡± > 4) Additive screen based on the original condition > 5) Check the original plates for other crystallizing conditions > (unfortunately until now this is the only one out of ~300) > 6) Screen with other forms of the protein, i.e., N/C-terminus truncated > ones, complexed with its ligands etc. > > I believe many protein crystallographers have encountered similar > problems, are there any successful stories from these fancy poor crystals? > Any suggestions or references will be highly appreciated. > > Thanks in advance! > > Tiancen Hu > Shanghai Institute of Materia Medica > Rm. 2107, #555, ZuChongzhi Rd. > Shanghai 201203 > P.R. China > Tel: +86-21-50806600 ext 2107 > Email: [EMAIL PROTECTED] > >
