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Re: [ccp4bb] How to reduce no. of overlaps

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999
Previous message:
Subject: Re: How to reduce no. of overlaps
From: Frank von Delft frank {- dot -} vondelft {- at -} SGC {- dot -} OX {- dot -} AC {- dot -} UK
Date: 2012-03-07
Next message:
Subject: Re: How to reduce no. of overlaps
From: Jim Pflugrath Jim {- dot -} Pflugrath {- at -} RIGAKU {- dot -} COM
Date: 2012-03-07


Subject: Re: How to reduce no. of overlaps
From: Zhijie Li zhijie {- dot -} li {- at -} UTORONTO {- dot -} CA
Date: 2012-03-07

Hampton sells an adjustable mounted loop for this purpose.

http://hamptonresearch.com/product_detail.aspx?cid=24&sid=136&pid=385


From: Frank von Delft
Sent: Wednesday, March 07, 2012 1:26 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] How to reduce no. of overlaps


You probably have to tilt your crystal, so that the long axis is parallel to the beam. We do this routinely: cut a plastic pipette tip to have a sharp point, then push the loop where it attaches to the pin, to bend the crystal itself.

You have to identify from your diffraction whether the long axis is pointing through the face or the edge of the loop. As it's P6, chances are it's through the face, because long-axis P6 tends to make flat hexagons which lie flush with the face. So you have to bend so the face of the loop upwards.

You'll have to practice this first, though, so put up an empty loop. Top tips:
* Don't breathe! You'll blow the cryostream away.
* Bend the loop towards (rather than away from) the rim edge of the pin to which it's glued.
* Don't breathe!
* Practise practise practise.


Another thing: most in-house sources allow you to reduce divergence of the beam. You lose intensity, but no matter, just expose longer. That also improves overlap.

Cheers
phx



On 07/03/2012 04:56, Dipankar Manna wrote:
Dear Crystallographers,



I am working on a protein having SG P6, the cell parameters are a= 79, b= 79, c= 325. The crystals are forming in big size and with very good shape. It also diffracting very well in Home source facility both in terms of resolution and intensity. But the only problem is the number of overlaps. Its showing much more than the good spots. As a result the completeness is showing maximum up to 65% even after collecting 180 degrees. I am unable to get a complete data. I tried with reducing the oscillation angel to 0.3 degree/0.5 degree but it did not improve that much. Please give me some suggestions.



Regards,



Dipankar





Dipankar Manna

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CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999
Previous message:
Subject: Re: How to reduce no. of overlaps
From: Frank von Delft frank {- dot -} vondelft {- at -} SGC {- dot -} OX {- dot -} AC {- dot -} UK
Date: 2012-03-07
Next message:
Subject: Re: How to reduce no. of overlaps
From: Jim Pflugrath Jim {- dot -} Pflugrath {- at -} RIGAKU {- dot -} COM
Date: 2012-03-07



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