[ccp4bb]

- Protein crystallography

Main steps:

- Protein purification
- Crystallisation

Special:

- Programs for crystallography
- X-ray detectors

Basic tutorials:

   - Chemistry
   - Protein
   - Peptide
   - Amino Acids

Xtal community:

- CCP4BB

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

Previous message:
Subject: Re: long command line problem in ccp4i/scala
From: "P {- dot -} J {- dot -} Briggs" p {- dot -} j {- dot -} briggs {- at -} DL {- dot -} AC {- dot -} UK
Date: 2007-06-08

Next message:
Subject: Protein Crystallographer at Merck Research Laboratories
From: "Becker, Joseph W" joseph_becker {- at -} MERCK {- dot -} COM
Date: 2007-06-08

Subject:
From: Marius Schmidt marius {- dot -} schmidt {- at -} PH {- dot -} TUM {- dot -} DE
Date: 2007-06-08

Dear Experts,
I have a strange problem.
Recently, we have collected some data on some myoglobin
derivative. Crystals were quite twinned and we had to
cut a leavlet out of a bundle of crystals.
Crystal scattered to 2.6 A. Apparent space group
P212121 with paramters [in A]: 30 58 and 118.
One single mol-rep solution was found with
sig to noise of rotation: 17
sig to noise of transl: 15
In two dimensions molecules pack nicely (see attached
image vowi34.gif) in the other direction there is much to much
space between the layers of molecules that one could
envision proper crystal packing (see other image vowi32.gif).
And indeed: refinement stops with R-cryst/R-free ~34/42 [%]
with some spurious e-density outside the molecule which does
not look like water.
Matthew coefficient: 2.8 with one mol per asy unit.
I tried to find another MR solution with the first
one fixed and I failed (signal to noise of the best
Rot and Trans solutions around 3).
What could be the problem? I always thought that
twinning cannot be the reason in P212121. Density
distributions (from truncate) however seem to indicate
some degree of twinning although this might also be
a problem of data processing (data are quite weak).
Maybe some of you have encountered similar problems and
know how to solve them. Any hint very much wellcome.

Marius

CCP4bb navigation

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

Next message:
Subject: Protein Crystallographer at Merck Research Laboratories
From: "Becker, Joseph W" joseph_becker {- at -} MERCK {- dot -} COM
Date: 2007-06-08