crystal size

Dr. Artem Evdokimov eudokima at mail.ncifcrf.gov
Wed Mar 28 12:01:09 EST 2001


Hi,

My 2 cents:

I have collected 2.4 A data from 0.05x0.03x0.03 mm crystals at
Brookhaven, line X9B. This was not a small protein, by the way, 47 kDa
in unit cell.
Exposure time was 5 minutes per degree, which is very long for
synchrotron. At Argonne, I could have gotten away with much less
exposure and probably higher resolution. Plus, they have a microcrystal
beamline with special optics for accurate centering and such.

I hesitate to call crysals 'too large' however it is certainly true that
very large crystals are very difficult to freeze. In general anything
above 0.5 is difficult. I am currently growing 2 mm protein crystals for
neutron experiments and I have yet to figure out how to freeze them.

Practically, if I were you I'd just shoot your crystals and see what
happens. Make sure that you are as close to the center of the beam as
possible - for very small crystals it makes a lot of difference.

Michael Witty wrote:
> 
> Dear All,
>         I am starting on some practical crystallization and have obtained
> some protein crystals which people have called "small".  They are about
> 30 micrometers.  What do you all think the words "big" and "small" mean
> regarding protein crystals.  Or is that unimportant, and do we have to put
> the crystal into an x-ray beam to find out if it is a "good" protein?
> Regards, Mike.

-- 
|Dr. Artem Evdokimov   Protein Engineering |
| NCI-Frederick        Tel. (301)846-5401  |
|              FAX (301)846-7148           |
|        eudokima at mail.ncifcrf.gov         |
|      http://www.ncifcrf.gov/plague       |





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