Re: [ccp4bb] twin fraction varies between crystals?

- Protein crystallography

Main steps:

- Protein purification
- Crystallisation

Special:

- Programs for crystallography
- X-ray detectors

Basic tutorials:

   - Chemistry
   - Protein
   - Peptide
   - Amino Acids

Xtal community:

- CCP4BB

CCP4bb navigation

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

Previous message:
Subject: Re: twin fraction varies between crystals?
From: Peter Zwart PHZwart {- at -} LBL {- dot -} GOV
Date: 2007-04-17

Next message:
Subject: Re: twin fraction varies between crystals?
From: Manish C Pathak pmxtal {- at -} YAHOO {- dot -} CO {- dot -} IN
Date: 2007-04-17

Subject: Re: twin fraction varies between crystals?
From: Christopher Colbert Christopher {- dot -} Colbert {- at -} UTSOUTHWESTERN {- dot -} EDU
Date: 2007-04-17

I experienced the same behavior. Crystals from the same drop could have
varying twin fractions. Screening for twinning can be done with
remarkably few degrees of data. Of course, all proteins and all twins
aren't equal. So, don't expect to have varying twin fractions all the
time.

Happy Refining,

Chris

On Tue, 17 Apr 2007, Mark Mayer wrote:

>>>For cases where people have had merohedral twinning, did the twin fraction vary substantially
>>>between individual crystals grown under indentical conditions? I have no prior experience with
>>>merohedral twinning, and was surprised to see that the twin fraction varied substantially as detailed
>>>below, and that by screening we were able to get untwinned xtals.
>>>
>>>The project started with a weak home data set for which the twin fraction was 0.478, and which
>>>scaled in both H3 and H32. We just came back from APS with data sets from another three crystals,
>>>for which the ML twin fraction, estimated using phenix.xtriage with scalepack merged intensities as
>>>input, varied from 0.335, 0.219 and 0.02. The latter is refining very nicely, in H3 and will not scale in
>>>H32.
>>>
>>>Thanks - Mark
>>>

Christopher L. Colbert, Ph.D.
Assistant Instructor Phone: (214) 645 5944
University of Texas Southwestern Medical Center FAX: (214) 645 5945
6001 Forest Park Lane
Dallas, TX 75390

CCP4bb navigation

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

Previous message:
Subject: Re: twin fraction varies between crystals?
From: Peter Zwart PHZwart {- at -} LBL {- dot -} GOV
Date: 2007-04-17

Next message:
Subject: Re: twin fraction varies between crystals?
From: Manish C Pathak pmxtal {- at -} YAHOO {- dot -} CO {- dot -} IN
Date: 2007-04-17