Hi. Here is some additional information.
1. The purification method that I used included Ni, tag cleavage, and SEC as a final step. I have tried samples from three different purification batches that range in purity, and even the batch with the worst purity seems to produce crystals. 2. The protein is a proteolyzed fragment since the full length version did not crystallize. Mutagenesis and methylation, however, may be techniques to consider since the protein contains quite a few lysines. 3. There are not any detergents in the buffer, so these are not detergent crystals. The protein buffer just contains Tris at pH 8, NaCl, and DTT. 4. Some experiments that I have done thus far seem to suggest that the crystals are protein. Izit dye soaks well into the crystals, and the few crystals that I shot previously did not produce any diffraction pattern whatsoever. However, I have had difficulty seeming them on a gel and they are a bit tough to break. 5. I tried seeding previously as follows: I broke some crystals, made a seed stock, dipped in a hair, and did serial streak seeding. After seeding, I usually saw small disks or clusters along the path of the hair but nothing larger or better looking. I also had one more question. Has anyone had an instance where changing the precipitation condition or including an additive improved diffraction but did not drastically change the shape of the protein? If so, I may just try further optimization with the current conditions and shoot some more crystals. Thanks for all the helpful advice thus far, Matt
