Re: [ccp4bb] small lines in diffraction pattern

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

Previous message:
Subject: Re: OT: VectorNTI alternatives
From: Darren Hart hart {- at -} EMBL {- dot -} FR
Date: 2009-01-28

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From: Cynthia Kinsland clk10 {- at -} CORNELL {- dot -} EDU
Date: 2009-01-28

Subject: Re: small lines in diffraction pattern
From: "Nave, C (Colin)" colin {- dot -} nave {- at -} DIAMOND {- dot -} AC {- dot -} UK
Date: 2009-01-28

Margriet
This looks like stacking or shift disorder which can occur when perfect
3 dimensional order breaks down. For example one can have a situation
where the lattice is preserved in 2 dimensions but the planes can slide
with respect to one another destroying the order in the 3rd dimension,
thereby giving rods in reciprocal space rather than spots. Preservation
of order in 1 dimension but with the 1 D lattices shifted with respect
to each other gives diffuse planes in reciprocal space. If displacements
are non random, than the diffuse scatter might only occur for certain
reflections.

As sharp spots are also present, it is likely that the 3D order is
preserved over much of the sample. To analyse properly one would have to
record diffraction over small angular increments (similar to 3D
reciprocal space mapping) and perhaps identify the hkl value of
reflections which exhibit strong, weak or absent effects of this type.

The reason for the behaviour can become clear when the structure is
known and weak lattice interactions identified. However, if these
effects are preventing you determining the structure then this statement
is not particularly useful.

If really interested you can of course google for such types of
disorders and find examples with similar types of streaking (e.g. in J.
Appl. Cryst. (1971). 4, 329
http://journals.iucr.org/j/issues/1971/04/00/a08549/a08549.pdf
).
Alternatively read "ancient" text books such as Hosemann and Bagchi.

Others will be far better at suggesting means of preventing the effects,
which I suspect is what you would really like to know!

Colin

________________________________

From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of
Margriet Ovaere
Sent: 28 January 2009 13:52
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] small lines in diffraction pattern

Dear all,

In the diffraction pattern of crystals of an RNA decamer, small lines
appeared (see pictures attached). We've tried different crystals but
they all showed the same small lines. Has anybody seen this phenomena
before and has got an explanation for it please..?

Many thanks

Margriet Ovaere

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CCP4bb navigation

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

Previous message:
Subject: Re: OT: VectorNTI alternatives
From: Darren Hart hart {- at -} EMBL {- dot -} FR
Date: 2009-01-28

Next message:
Subject: Re: OT: VectorNTI alternatives - 4 Mac?
From: Cynthia Kinsland clk10 {- at -} CORNELL {- dot -} EDU
Date: 2009-01-28