There's no theoretical reason it can't be that long.
BUT it is possible, especially for problematic diffraction
patterns (e.g. from a badly-diffracting, cracked crystal)
for the software to pick some wacky value in its attempt to
fit spots that don't really all belong in the same pattern.
You should be able to tell by looking at the images - are
there rows of spots regularly spaced 1/652 A apart?
Phoebe
---- Original message ----
>Date: Tue, 3 Aug 2010 10:27:34 -0400
>From: Matthew Franklin <[log in to unmask]>
>Subject: Re: [ccp4bb] Extremely long c-axis...reasonable?
>To: [log in to unmask]
>
>Hi Christian -
>
>As a number of others have pointed out, this unit cell is
unusual, but not impossible. It is, in fact, possible to
search the PDB for unit cell parameters. From the home
page, choose "Advanced Search"; on the search page,
choose "X-ray cell dimensions" from the dropdown list of
query types.
>
>Performing this search finds 12 structures in the PDB with
c axis > 600 A and a and b axes < 100 A. Two of these are
fiber diffraction molecular envelopes, but the other 10 are
well-refined crystal structures at reasonable resolutions.
So it can be done!
>
>- Matt
>
>
>--
>Matthew Franklin , Ph.D.
>Senior Scientist, ImClone Systems,
>a wholly owned subsidiary of Eli Lilly & Company
>180 Varick Street, 6th floor
>New York, NY 10014
>phone:(917)606-4116 fax:(212)645-2054
>
>
>> -----Original Message-----
>> From: CCP4 bulletin board [mailto:[log in to unmask]]
On Behalf Of
>> Christian Strube
>> Sent: Tuesday, August 03, 2010 7:46 AM
>> To: [log in to unmask]
>> Subject: [ccp4bb] Extremely long c-axis...reasonable?
>>
>> Hi everybody,
>>
>> indexing of recently collected data gave me unit cell
parameters of
>> a=b= 88 and an extremely long c-axis of 652 A. My
question is, if the
>> value of the c-axis can be reasonable? Or am I wrong with
the SG? I
>> know that length doesn't count, but does anybody has a
longer one? Is
>> there a function in the pdb to look for the length of
axes?
>>
>> Thanks,
>>
>> Christian
>>
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>Thank you.
Phoebe A. Rice
Assoc. Prof., Dept. of Biochemistry & Molecular Biology
The University of Chicago
phone 773 834 1723
http://bmb.bsd.uchicago.edu/Faculty_and_Research/01_Faculty/01_Faculty_Alphabetically.php?faculty_id=123
RNA is really nifty
DNA is over fifty
We have put them
both in one book
Please do take a
really good look
http://www.rsc.org/shop/books/2008/9780854042722.asp
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