We have used the PEI precipitation described by Pavan, very high salt (2M or
even higher) as alluded to by Ana, or heparin columns with success. In some
cases, a denaturing purification protocol can be very useful, but of course
this assumes you can refold the protein. In the case of a student
Tiancen,
How critical is it that the crystals remain in the sulfate salts? I ask
because we recently had success with an RNA crystal that was very
intractable to heavy atom soaks because of very high lithium sulfate
growth conditions, and the fact that cryo-protection was best done by
increasing
