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Yup. Typical example is the crystallization of CAT (chloramphenicol acetyl
transferase) out of protein preps derived from bacteria that carried CAT for
selection (common marker in the older days, currently primarily used for
e.g. LysS, LysE, RIL, and other auxiliary plasmid maintenance). I have
actually seen it happen to someone, not a happy story.
However, I have not heard of impurities crystallizing out if their original
concentration was not at least 5-10% of the whole protein prep. That's why
MS verification of protein samples and (if suspicions arise) dissolved
crystals is a good thing to do.
Artem
----- Original Message -----
From: "Edward A. Berry" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, September 14, 2005 10:49 PM
Subject: Re: [ccp4bb]: Imidazole in crysatllization
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Artem G. Evdokimov wrote:
On the other hand, people will readily share horror stories about how
proteins only would crystallize for them once the purity exceeded a
magical percentage, or once a specific pesky impurity was removed, a
magical purification step was added, etc. Therefore, it is best to go
with the protein and figure things out practically :)
Or how a trace impurity crystallized when the target protein didn't,
and the mistake was only realized after MR failed,
MIR succeeded, and the density improved to the point where enough
sequence could be read off to identify it by blast.
Ed
