Well - it is hard to comment without more information, but many crystals do have tNCS and yield perfectly satisfactory solutions..
How many molecules do you expect in the asymmetric unit? Look at the Matthewscoefficient suggestions to guess that. What are the fractional coordinates of the Patterson peaks? If they are near 1/2, 1/3 etc they can cause whole classes of reflections to be systematically weak and that guarantees higher R factors. Do you also have non-crystallographic rtations (MOLREPs self rotation plot is helpful here.. ) Anyway get back to us with more information if you like. Eleanor On Wed, 19 Jul 2023 at 15:46, Jon Cooper < [email protected]> wrote: > Hello Lande, the map which you have fitted looks quite good, as does the > diffraction pattern. At that resolution it will benefit from anisotropic > refinement, I think. What sort of R-and R-free do you have? You mentioned > they are high with some of your solutions. What does the solvent content > suggest for the number of molecules per asymmetric unit and have you found > them all? With MR, there is usually a bewildering array of peaks with the > same height, due to the high symmetry of the translation function. The > programs will sort that out for you, usually. Is that what you mean with 48 > solutions? Are you sure of the space group? The main MR progs can try all > possibilities, I think, so I assume you have done this. Also, my first and > most memorable encounter with tNCS was with a crystal which had an NCS > 2-fold parallel with a crystallographic 2(1) screw-axis. To my mind tNCS is > just rotational NCS with a screw translation? Others will probably disagree > ;-0 > > Best wishes, Jon Cooper. [email protected] > > Sent from Proton Mail mobile > > > > -------- Original Message -------- > On 18 Jul 2023, 10:06, Lande < > [email protected]> wrote: > > > How to deal with tNCS? Dear all, I have read topics talking about tNCS > problem a few years ago and have faced many tNCS data during my work. > Generally, I just turned that tNCS button on in phaser during MR, and > ignored high R/R-free if the MR solutions were correct. However, I always > thought about what made tNCS to occur and what I can do further on tNCS > data. Recently, I got sub 1.5A diffraction data of a simple protein (~100 > amino acid) soaking with a large ligand and it seems it suffers severe > tNCS. It is very clear that two of its unit cell axis are doubled and there > is many ghost density around the model. The other 10 datasets with > different soaking time and concentration do not have tNCS, No ligand in > there after modeling. So all my hope lays on that tNCS one. Here are my > questions: 1. I know some proteins tend to form tNCS crystal but what > causes tNCS in this crystal only? 2. In MR 48 solution were found and > currently I have 4 copies in ASU. There seems to be more to fit the empty > density. The map is messy and I cannot determinate the ligand status. What > can I do now? Here I linked some screenshots. Any suggestions or articles > to read will be helpful. Regards, Lande Fu > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?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/
