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1. Pick many representative samples from each morphological class. 2. Take as many notes about the appearance, habits, and physical properties of each crystal that you can. 3. Screen every crystal for diffraction in a variety of cryo- protectants, etc. 4. All protein crystals were meant to be destroyed in an x-ray beam pointed at a detector. 5. Salt has a characteristic diffraction. X-ray is the best way to test for salt. 6. If you can unambiguously identify salt crystals from the information you gathered in 2, 3, and 5, don't waste time harvesting said salt crystals. 7. Go to 1 until you have exhausted your supply of protein crystals. 8. Grow new crystals by varying growth conditions. 9. Go to 1 until you are happy with your data. James On Jan 13, 2009, at 7:50 PM, deliang wrote: > Hi there, > > Since a lot of different forms of crystals shows, I am using a quick/ > simple strategy to choose crystals by applying a force on the > crystal against the wall, with the nylon loop. > > Some can never break apart, so they are salt crystals? The others > can not survive the force and lose their intact shape and sharp > surface. It seems these are protein crystals, but are they "bad" > crystals? I just came to this field, and welcome all your > suggestions and experience. > > Thanks a lot. > > Deliang