I have a protein-DNA complex grown in 30 -40% MPD/0.2M Ammonium
sulfate/5% PEG 400/ 0.1M Tris (8.5).
...
I tried to grow crystal without AMSO4 or 0.1M AmSO4, but no crystals was
shown up.
So how would you test the following four hypotheses?
1. Sulfate is not required, ammonium is.
2. Ammonium is not required, but sulfate is.
3. Some salt is required to increase the ionic strength, but
it does not have to be ammonium sulfate.
4. Ammonium sulfate helps with crystal nucleation, but is not required for
crystal growth.
