First comment - your data looks excelent - even to 1.8A. Second - look also at the wilson plot and second moment plots - these should not be jerky - wilson plot falling off smoothly, 2nd moment pretty constant to the good resolution limit..
Thirdly - just use all your data and check the refinement results. You can always reject some later if the refinement looks bizarre. Eleanor On 4 August 2017 at 15:37, Harry Powell <hrp-ccp...@virginmedia.com> wrote: > Hi Satvik > > If you're only just starting out, the first thing I would recommend is > that you forget all about Scala! It's been effectively obsolete for 5-6 > years, and any bugs that exist in it will not be fixed. > > It was replaced by Aimless a long time ago; Aimless is much faster than > Scala and the scaling model is somewhat improved (what would you expect > with another half-decade of development?). > > Cutting your data at the data processing stage is probably too early in > the structure solution process. > > In your case, I'd continue analysing your structure with all your data (to > 1.861Å,) after re-scaling with Aimless ;-), then once the structure is > complete and refined, use the "paired refinement" technique to see if the > high resolution data are actually contributing any useful information. > > HTH > > Harry > -- > Dr Harry Powell > Chairman of International Union of Crystallography Commission on > Crystallographic Computing > Chairman of European Crystallographic Association SIG9 (Crystallographic > Computing) > > > > On 4 Aug 2017, at 13:48, Satvik Kumar wrote: > > Dear Crystallographers, > > > I am a beginner to solving structures by x-ray crystallography. Having > collected a diffraction data set using laboratory source X-ray, I am now > processing the data. I have integrated the data successfully with the > program iMOSFLM using the space group P212121. > > > During the process of scaling and merging intensities using Scala, I was > confronted with the question of setting the resolution cutoff. To clear the > doubts I had, I have read the below articles with great care: > > > 1. How good are my data and what is the resolution? Evans and Murshdov, > 2013. > > 2. Assessing and maximizing data quality in macromolecular > crystallography. Karplus and Diederichs, 2015. > > > Based on these articles it becomes very clear that I should set the > resolution cutoff to a value at which CC1/2 reduces to 0.2-0.4 irrespective > of the values of either Rmerge or I/sigI (prone to uncertainities). > > > When I ran the program Scala using high resolution cutoffs ranging from > 1.861 A (resolution at which data was collected) to 2.33 A, I observe that > at 2.0 A, the CC1/2 is 0.582 (outer shell) but the CC1/2 increases to 0.722 > at 1.861 A. > > > The Karplus and Diederichs article clearly states that the CC1/2 is 1 at > low resolution and drops down with increasing resolution. It also states > that any anomaly should be carefully inspected. > > > I request the community to kindly inspect the statistics and guide me in > setting the optimum resolution cutoff. I have attached a pdf file > containing the Scala outputs (statistics and a plot of correlation > coefficients versus resolution) for your inspection. > > > > Thanks, > > Satvik > <040817_scala.pdf> > > >
