What else in in the conditions? Calcium Sulphate/Phosphate is poorly soluble, so if there is any sulphate or phosphate in your condition I would be suspicious. The age of the plate is also a bad sign, as evaporation over an extended time can lead to salt crystals. Check the well solution for crystals, if there are any then it's almost certainly salt. Softness and lack of birefringence are cautiously good signs, however the only way to know for sure is to stick them in an x-ray beam, which is always worth while for a crystal.
Good luck Rhys ________________________________________ From: CCP4 bulletin board [[email protected]] On Behalf Of Careina Edgooms [[email protected]] Sent: 15 April 2013 11:18 To: [email protected] Subject: [ccp4bb] salt or not? Dear ccp4 I have been performing trials on a protein DNA complex for a while now and have not seen any crystals form. Today I checked an old plate (over a month old) and I see 4 large crystals. *excitement* Three of them look tetragonal in shape (like a pyramid) and one of them looks hexagonal. I do not know if they are salt or protein. There is calcium chloride in the buffer. They feel quite soft to touch. They do not cause much birefringence. One of them does not seem to absorb much izit. It did go a bit blue but not entirely. How can I tell if this crystal is protein or not? Do you think its worth trying to see how it diffracts? Also, does Izit affect diffraction/ protein structures at all? Could I use a crystal with Izit in a diffraction experiment and ultimately to get the structure? Best Careina
