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Have you worked out where the long axis is with respect to the crystal shape? As Jacob said, it’s likely to be parallel to the short axis of the crystal, which would mean that it’s almost impossible to mount crystals in normal loops with this axis along the pin. You’ll want to rotate along this long axis (within 30º) during data collection to prevent overlaps, which may mean mounting crystals in a bent loop, using a kappa goniometer, or what I guess might be the easiest/best, a multi-axis goniometer, like they have at the Swiss Light Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4489532/ (haven’t been there myself unfortunately, and I don’t know if they have these elsewhere) Even though your native data is apparently ok, it may also get better if you use this strategy. Mark J van Raaij Dpto de Estructura de Macromoleculas Centro Nacional de Biotecnologia - CSIC c/Darwin 3 E-28049 Madrid, Spain tel. (+34) 91 585 4616 http://wwwuser.cnb.csic.es/~mjvanraaij > On 4 Aug 2016, at 22:58, Mohamed Noor <[log in to unmask]> wrote: > > Dear all > > I am trying to get an anomalous dataset at Fe K edge for my protein. While I can routinely get native datasets to a resolution of 2.5-3 A, the high radiation damage coupled with non-isomorphism is preventing me from getting a high multiplicity anomalous dataset. The best that I have got so far has an anomalous signal to 4.5 A but this was not enough for phasing (I tried CRANK2 and phenix.autosol) with various options. > > The SG is C 2221, with unit cell of about 130, 420, 85. Secondly, the crystals are not perfectly shaped like those 'usual' ones. On one side, they are almost flat like a flying saucer (for a lack of better description). The Rmerge then becomes wavy every 80 degrees or so. > > The protein is about 60 kDa with 5 Fe (mixture of heme and [Fe-S]) per monomer. The synchrotron has a PILATUS detector. > > Are there any helpful hints that you can share? > > Thanks. > Mohamed