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Hi Paul, R/R-free in the mid to low 30's at 2.6 angs resolution from only 50% of the scattering mass of your asu already indicates that your model is largely complete and that the expected second trimer does not contribute much to your signal, i.e it is grossly disordered. If your structure indeed suffers from such extreme disorder your data would likely suffer from significant anisotropy. What does your output from Truncate say about that? Could you also comment on the quality of the difference fourier maps (2Fo-Fc contoured at 0.8-1 sigma and the Fo-Fc contoured at 3 sigma) in the region of the missing trimer? Is there any alectron density to be seen? Can you identify some secondary structure elements in the second trimer? If you could see some structure maybe you could try deriving some NCS relationships that will eventually allow you to enhance the density of the missing trimer by NCS averaging. If NCS does apply in your case then you can expect an increase in the signal to noise ratio in the region of the missing trimer by as much as as the square root of n, where n is the number of molecular units being averaged. Your already modeled trimer could serve as a good model to capture the envelope for your second trimer. Programs like G. Kleywegt's MAMA could help you easily go from model to density envelopes. ----- Savvas -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Widboom Sent: Wednesday, August 30, 2006 7:15 PM To: [email protected] Subject: [ccp4bb]: more details on Half solution *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** The resolution of the data is 2.6A. The single trimer model refines very well but only to R = 33% Rf = 35%. At this point the trimer cannot be refined anymore, it is virtually complete with few conformational violations. I understand that this second trimer is not twinned, and is probably in a state of disorder. Finding this second trimer is important, first of all to lower the R factors to an acceptable range, second of all to establish contacts between the rows of symmetry related molecules from the first trimers. When looking at the single trimer it is obvious something must fit in that region. Thanks for you help. Sincerely Paul Widboom Boston College
