Dear Crystallographers,
has anyone heard of or seen crystals form in their membrane protein stocks
in the presence of DDM, such as from a breakdown product, or otherwise? My
protein stock, after having been stored at ~2mg/mL (around solubility limit)
at 4degC in (theoretically) nothing but ~5mM DDM and 10mM NaHEPES 7.0,
formed a significant, visible number of spontaneous crystals in the bottom
of the tube (two separate, identical aliquots) after ~5mos. I have heard of
spontaneous crystals for soluble proteins, but never for membrane proteins.
The protein was buffer-exchanged into (10mM HEPES 7.0 and 1mM DDM) by 2 x
30-fold then 1 x 15-fold concentration-dilution in 50kD MWCO concentrator.
Seems pretty thorough to me, but perhaps there was some kind of carry-over?
Substances encountered in the course of the prep:
HEPES
NaCl
protease inhibitor cocktail
EGTA
DNAse
TCEP
PMSF
LysoPhosphosphotidylCholine 16
DDM
imidazole
glycerol
Thanks,
Jacob Keller
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Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
Dallos Laboratory
F. Searle 1-240
2240 Campus Drive
Evanston IL 60208
lab: 847.491.2438
cel: 773.608.9185
email: [EMAIL PROTECTED]
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