Hi, Re " Has anybody ever used xenon? Can anyone share the starting pressure and time for optimization? " This paper :- doi:10.1107/S0907444901009350 <http://dx.doi.org/10.1107/S0907444901009350> offers you details. Best wishes, John
On Fri, Apr 17, 2015 at 2:11 AM, joy yang <joybeiy...@gmail.com> wrote: > Hi All, > > Thanks a lot for the advice from Mark. > > 1. For the comment to use a attenuated beam, the major concern here is > resolution, since at full beam, the resolution is already somewhere > between 3.5-4.2, I assume that significant attenuation will bring down the > resolution dramatically, and also decrease the I/Sigma which might lead to > more errors in |F|? > > 2. We used TaBr because as a large electron dense cluster, it is good for > low resolution phasing. This derivative, in the best scenario, give a 4.8A > data set (a resolution that is supposed to be enough to find the huge > cluster) which only has 0.1~0.2A unit cell difference to a native data set > collected on the same beam, theoretically, this dataset should give > prominent peaks on hacker section (the crystal is green, and fluoresence > scan give moderate signal), but what I find is only two small peaks (6-7 > sigma, boarder line) (maybe occupancy too low?), and using Hyss to find the > HA only result in a FOM of 0.20. This is what triggers me to wonder if a > high scaling error model (0.05-0.1) is also detrimental for isomorphous > phasing? > > 3. speaking of Se. Is it possible to use Se as a second derivative for MIR > in my case (500 amino acid, 18 Met)? my concern is that Se might be too > “light” for my protein, and 4.5A resolution is NOT much better than the 7A > Mark has mentioned. > > 4. Has anybody ever used xenon? Can anyone share the starting pressure and > time for optimization? > > Thank you again, > > Bei > -- Professor John R Helliwell DSc
