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[ccp4bb]: soluble protein, jeffamine, loops,panjelly

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save'm up and ask all at one time time

does anyone have special tricks to crystalize very soluble protein;
esp. a complex that can disassociate?  already in the pipeline:
titrating with precipitants, establishing the pH range to retain
intact complex.

I have a protein that crystalizes out of 18-25% Jeffamine M600 (CSII-31)
that is bulletproof to derivatization. we have varied pH, soak time,
conc. of HA. we have tried xenon , cryo-soaking with halides and 
iodination with diiodoacetic acid.  the only structures i have found
with crystal grown from JA (and all lower conc's) were mol. repl. solutions.
anyone have experience with JA (M600 in particular)?

I have convinced myself that my cryo-loops move as the goniometer head
rotates.  as i align the crystal under the telescope i can see it move 
as i rotate it 180 degrees to center it(this apears to be a horizontal
translation).  I have also observed that when performing an inverse beam
exp't that the rotx,roty,rotz (denzo notation) change significantly
(as much as 3 degres) when the 180 deg rotation occurs and then when
the rotation back 180 degrees happens the rotx... angles change back
also.  our LN2 nozzle is inclined about 45 degrees wrt Phi axis.
this effect is decreased when the twisted part of the loop is entirely
buried in epoxy but this also makes for a real battle when fishing the
crystal out of the drooplet.  

is this a problem with the end-on configuration of the nozzle as well?

since in usual practice this is a very gradual movement, is it producing
bad data or just large std dev's.

and last has anyone other that panjelly's parents have any success
stories with this stuff?

Steve Ernst
Univ. of Texas
Dept. of Chemistry & Biochemistry
Austin, Tx