Working Solutions and Magic Solutions
A precipitant is defined as a solution which is used to induce supersaturation.
A precipitant will consist of a precipitating salt or polyethylene glycol, a buffer and some additives.
In reverse screening we arrive at a refined precipitant solutions through several steps. The intermediate
solutions are called working solutions, while the final refined solution is refered to as "Magic Solution".
There is no magic in it. It is the result of a lot of hard work, but it humors many that think
that in order to do crystallization one must have a "green finger" or practice some kind of witchcraft.
They also believe that like the three witches in Macbeth "The First witch stirs the pot and gets first authorship,
but only on the crystallization paper, the second witch decides which magic ingredients to add,
and the third witch supervises and is generally last author
on all the papers and first on all the reviews.
Back to science:
Working Solutions
A working solution is mixed in a volume which may range from 50 ml to 500 ml. The precipitant concentration is
set at about 10% above the amount needed to generate nucleation. It provides a more accurate method to determine
the effect of small amounts of additives. These additions are refered to as perturbations.
As specific effects and additives are
identified, it becomes important to include in the precipitant mixture. Such compounds are used to help in controlling
supersaturation levels, nucleation and crystal growth. Such a mixture, is the new working solution and it can
be used to analyse other additives which can then be included.
Magic Solutions
Magic solutions are the final product of an optimization. It is used to grow crystals for heavy atom searches.
It is also used to compare different preparations that should be the same. It is also used to find crystallization
conditions for different complexes of the same protein. They are also used in the screening of new macromolecules
with smimilar characteristics in the same way you would use one particular condition from the
Hampton Screen.
Updated/Created on Sep-23-97 by EAS,
TSRI