I've used a technique called "annealing", which amounts to holding an index card between the cryo stream and the crystal for a few seconds then removing the card quickly.
In my experience, about 70% of the time the diffraction is worse and about 30% of the time the ice rings will be gone with slightly improved diffraction, allowing recovery of a significant range of data. Most of the time, though, I find another crystal that had a better initial freeze, so annealing has never been a life saver--but it could be under dire circumstances. James On Oct 11, 2011, at 9:30 AM, Dr. Thayumanasamy Somasundaram wrote: > Francis, > > I would like to bring your attention to our paper in Acta Cryst D Volume 66 > (6), 741-744 (2010) where we deal with spots under the ice-rings. We have > been very successful in eliminating the ice-rings and recover the data > underneath. If you are interested you can request the Python script from > Michael Chapman at OHSU. > De-icing: recovery of diffraction intensities in the presence of ice rings, > Michael S. Chapman and Thayumanasamy Somasundaram > > > If you need help please e-mail me outside the CCP4BB. > > On 10/11/2011 11:16 AM, Francis E Reyes wrote: >> >> All, >> >> >> So I have two intense ice rings where there appear to be lattice spots in >> between them. >> >> I understand that any reflections that lie directly on the ice ring are >> useless, however, how do software programs (HKL2000, d*Trek, mosflm, XDS) >> deal with these intermediate spots? >> >> It would seem to me that employing a 'resolution cut off' just before the >> ice ring (on the low resolution side) would be improper, as there are spots >> on the high resolution side of the ice. (see enclosed .tiff) >> >> >> In fact, how do these programs deal with spots lying on ice rings? Are they >> rejected by some algorithm by those programs during integration, or is it up >> to the scaling/merging (by SCALA for example) step to deal with them? >> >> Thanks! >> >> F >> >> >> >> --------------------------------------------- >> Francis E. Reyes M.Sc. >> 215 UCB >> University of Colorado at Boulder >> >> >> >> >> > > -- > > Dr. Thayumanasamy Somasundaram [Soma] > Director, X-Ray Crystallography Facility (XRF) > Off. Ph: (850)644-6448 | Lab Ph: (850)645-1333 > Fax: (850)644-7244 | E-mail: tsomasunda...@fsu.edu > > URI: www.sb.fsu.edu/~soma | URI: www.sb.fsu.edu/~xray > ----------------Postal Address-------------------------- > 91, Chieftan Way | KLB 414 > Institute of Molecular Biophysics > Florida State University > Tallahassee, FL 32306-4380, USA. > --------------------------------------------------------
