But if you only have a single diffracting crystal, then you don't know the space group before the experiment, and you have to collect 180 (native) or 360 (anom) anyway. Plus, I have seen too many sorry cases where people thought they had a certain space group, and later it turned out to be lower symmetry - happens e.g. for twinned crystals. These cases ended up with severely incomplete datasets. Finally, there is simply no downside in collecting more degrees with proportionally lower dose on the Pilatus. Merging the data recovers the _same_ signal. It has only advantages - so many that I won't write them up here with 1 finger on my tablet.
With a CCD it's a different story. Best, Kay Am 17. April 2015 15:49:21 MESZ, schrieb Jurgen Bosch <jbos...@jhu.edu>: >I would disagree. >My philosophy is: assume this is your only diffracting crystal, >maximize the outcome by investing some thoughts into it before being >sorry. Therefore, run strategy and optimize for anomalous pairs being >collected as close in time as possible. >If you have the luxury of having multiple crystals you know diffract, >then it;s a different story. > >Regarding the 1degree option, I think that dates back to the dinosaurs >of crystallography, when only non-decimal numbers were an option to be >entered in the CLI, yes there was no GUI before :-) Also the >goniometers are much more accurate these days. More seriously, I think >this had something to do perhaps with the cost of storage, remember 50 >MB was a lot of space 20 years ago. Your average Pilatus data set today >comes at 3-5 GB, considering a 6TB drive costs about 250$ today that’s >nothing. Or reading the files from a DAT4 drive took ages, so you >really didn’t want to collect fine sliced data. > >Jürgen >...................... >Jürgen Bosch >Johns Hopkins University >Bloomberg School of Public Health >Department of Biochemistry & Molecular Biology >Johns Hopkins Malaria Research Institute >615 North Wolfe Street, W8708 >Baltimore, MD 21205 >Office: +1-410-614-4742<tel:%2B1-410-614-4742> >Lab: +1-410-614-4894<tel:%2B1-410-614-4894> >Fax: +1-410-955-2926<tel:%2B1-410-955-2926> >http://lupo.jhsph.edu > >On Apr 17, 2015, at 9:25 AM, Kay Diederichs ><kay.diederi...@uni-konstanz.de<mailto:kay.diederi...@uni-konstanz.de>> >wrote: > >Hi Jürgen, > >sorry - that's what I get when mailing while boarding ... No, I'd just >collect 360 degrees, and if the crystal is still ok, another 360, ... >This way one >- obtains high completeness and multiplicity >- can discard frames with "too much" radiation damage >- does not have to worry about the starting point of data collection. >To make the most of the second 360°, you should change some parameter: >wavelength, rotation axis (requires a BL with kappa or Prigo), or at >least distance (by few percent). > >When I read that 1° frames are collected, I just wonder why? Because it >used to be done like that in the good old times? > >HTH, > >Kay > >On Fri, 17 Apr 2015 11:55:42 +0000, Jurgen Bosch ><jbos...@jhu.edu<mailto:jbos...@jhu.edu>> wrote: > >Just to clarify, I think what Kay meant with "strategy" is that you >don't just shoot at the crystal and collect. You should figure out what >is the optimum start and end point of your data collection. Best to be >cautious and not immediately go for highest resolution and not fry your >crystal. A 4 A complete anomalous data set is better than a partial >3.2A one. >J?rgen > > >...................... >J?rgen Bosch >Johns Hopkins University >Bloomberg School of Public Health >Department of Biochemistry & Molecular Biology >Johns Hopkins Malaria Research Institute >615 North Wolfe Street<x-apple-data-detectors://4>, W8708 >Baltimore, MD 21205<x-apple-data-detectors://5/0> >Office: +1-410-614-4742<tel:%2B1-410-614-4742> >Lab: +1-410-614-4894<tel:%2B1-410-614-4894> >Fax: +1-410-955-2926<tel:%2B1-410-955-2926> >http://lupo.jhsph.edu<http://lupo.jhsph.edu/> > >On Apr 17, 2015, at 06:37, Kay Diederichs ><kay.diederi...@uni-konstanz.de<mailto:kay.diederi...@uni-konstanz.de>> >wrote: > >Hi, >I'd say using a Pilatus detector in fine-slicing mode and lowdose/high >multiplicity will give you better chances to solve the structure. The >right strategy makes a difference ... >Best, >Kay -- Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail gesendet.
