Dear UPenn Crystallographer,
Regarding your concerns about twinning and how to deal with twinned
data, we did some work with twinned protein crystals a couple of years ago.
Our situation was perfect twinning by hemihedry, and we were able to
overcome the effects of the twinning. Your situation may be different,
but our work or the references we cite within it may help. Here is
Acta Cryst. (1993), D49, 375-380.
Most of the general and some specific consequences of twinning are described,
as are ways to detect it. Our paper deals with the very specific case of
perfect twinning. Partial twinning is more common (although probably still
quite rare) and is easier to deal with. Good luck. Contact me if you
run into problems.
redinbo at uclaue.mbi.ucla.edu