Re: [ccp4bb] Help with reducing crystal mosaicity

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

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Subject: Beam Time at BCSB beamlines in Berkeley
From: Paul Adams PDAdams {- at -} LBL {- dot -} GOV
Date: 2007-07-10

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Subject: Re: Help with reducing crystal mosaicity
From: Matthew {- dot -} Franklin {- at -} IMCLONE {- dot -} COM Matthew {- dot -} Franklin {- at -} IMCLONE {- dot -} COM
Date: 2007-07-10

Subject: Re: Help with reducing crystal mosaicity
From: Patrick Loll pat {- dot -} loll {- at -} DREXEL {- dot -} EDU
Date: 2007-07-10

Jeroen brings up a good point. Back in the old days, around 5 B. C.
(Before Cryo), we would use a chilled air generator to blow a stream
of cold air along the capillary axis to keep the crystals just above
their freezing point--it made a huge difference in crystal lifetime.
I recall a colleague devising an apparatus from a 50 ml conical tube.
The bottom was cut off and cold air was blown in from the other end.
Windows were cut in either side to allow the beam to pass & covered
in mylar. This way the entire capillary was contained within the
cold tube, so no temperature gradients formed along the length of the
capillary (temp gradient => distillation => dead crystal). Later, we
purchased a very clever goniometer head from Nonius that had a
plastic cylinder attached to goniometer head, with a swivel, so the
hose supplying cold air didn't get tangled during data collection...

I've often thought duplicating this apparatus when we encounter cryo
problems, but I'm always stymied when trying to find a cheap and
simple source of cold air. Any bright ideas?

On Jul 10, 2007, at 5:00 AM, mesters wrote:

> Mary,
>
> freezing habitually increases mosaicity. In your case, the high
> water content adds to the problem.
> Try not to freeze the crystal but collect at sub-zero temperature
> (in short glass capillaries or use oil plugs instead).
> You have to optimize the "close to freezing" data-collection
> temperature.
>
> I collected complete synchrotron datasets (of GCPII in buffer with
> PEG1500 and PEG400) at 260-263 Kelvin which resulted in mosaicity
> values of as small as 0.07 degrees! At 277 K, the crystals only
> last for a few images and freezing did not work (for the buffer
> mentioned before).
>
> - J. -

------------------------------------------------------------------------
---------------
Patrick J. Loll, Ph. D. (215) 762-7706
Associate Professor FAX: (215) 762-4452
Department of Biochemistry & Molecular Biology
Director, Biochemistry Graduate Program
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA 19102-1192 USA

pat.loll@drexel.edu

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Beam Time at BCSB beamlines in Berkeley
From: Paul Adams PDAdams {- at -} LBL {- dot -} GOV
Date: 2007-07-10